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[v4,1/3] kunit: make test->lock irq safe

Message ID 20210413100747.4921-1-glittao@gmail.com (mailing list archive)
State New
Headers show
Series [v4,1/3] kunit: make test->lock irq safe | expand

Commit Message

Oliver Glitta April 13, 2021, 10:07 a.m. UTC
From: Vlastimil Babka <vbabka@suse.cz>

The upcoming SLUB kunit test will be calling kunit_find_named_resource() from
a context with disabled interrupts. That means kunit's test->lock needs to be
IRQ safe to avoid potential deadlocks and lockdep splats.

This patch therefore changes the test->lock usage to spin_lock_irqsave()
and spin_unlock_irqrestore().

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Oliver Glitta <glittao@gmail.com>
---
 include/kunit/test.h |  5 +++--
 lib/kunit/test.c     | 18 +++++++++++-------
 2 files changed, 14 insertions(+), 9 deletions(-)

Comments

Brendan Higgins April 13, 2021, 1:38 p.m. UTC | #1
On Tue, Apr 13, 2021 at 3:07 AM <glittao@gmail.com> wrote:
>
> From: Vlastimil Babka <vbabka@suse.cz>
>
> The upcoming SLUB kunit test will be calling kunit_find_named_resource() from
> a context with disabled interrupts. That means kunit's test->lock needs to be
> IRQ safe to avoid potential deadlocks and lockdep splats.
>
> This patch therefore changes the test->lock usage to spin_lock_irqsave()
> and spin_unlock_irqrestore().
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Oliver Glitta <glittao@gmail.com>

Reviewed-by: Brendan Higgins <brendanhiggins@google.com>

Thanks!
Marco Elver April 13, 2021, 1:54 p.m. UTC | #2
On Tue, 13 Apr 2021 at 12:07, <glittao@gmail.com> wrote:
> From: Oliver Glitta <glittao@gmail.com>
>
> SLUB has resiliency_test() function which is hidden behind #ifdef
> SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody
> runs it. KUnit should be a proper replacement for it.
>
> Try changing byte in redzone after allocation and changing
> pointer to next free node, first byte, 50th byte and redzone
> byte. Check if validation finds errors.
>
> There are several differences from the original resiliency test:
> Tests create own caches with known state instead of corrupting
> shared kmalloc caches.
>
> The corruption of freepointer uses correct offset, the original
> resiliency test got broken with freepointer changes.
>
> Scratch changing random byte test, because it does not have
> meaning in this form where we need deterministic results.
>
> Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.
> Because the test deliberatly modifies non-allocated objects, it depends on
> !KASAN which would have otherwise prevented that.

Hmm, did the test fail with KASAN? Is it possible to skip the tests
and still run a subset of tests with KASAN? It'd be nice if we could
run some of these tests with KASAN as well.

> Use kunit_resource to count errors in cache and silence bug reports.
> Count error whenever slab_bug() or slab_fix() is called or when
> the count of pages is wrong.
>
> Signed-off-by: Oliver Glitta <glittao@gmail.com>

Reviewed-by: Marco Elver <elver@google.com>

Thanks, this all looks good to me. But perhaps do test what works with
KASAN, to see if you need the !KASAN constraint for all cases.

> ---
> Changes since v3
>
> Use kunit_resource to silence bug reports and count errors suggested by
> Marco Elver.
> Make the test depends on !KASAN thanks to report from the kernel test robot.
>
> Changes since v2
>
> Use bit operation & instead of logical && as reported by kernel test
> robot and Dan Carpenter
>
> Changes since v1
>
> Conversion from kselftest to KUnit test suggested by Marco Elver.
> Error silencing.
> Error counting improvements.
>  lib/Kconfig.debug |  12 ++++
>  lib/Makefile      |   1 +
>  lib/slub_kunit.c  | 150 ++++++++++++++++++++++++++++++++++++++++++++++
>  mm/slab.h         |   1 +
>  mm/slub.c         |  50 ++++++++++++++--
>  5 files changed, 209 insertions(+), 5 deletions(-)
>  create mode 100644 lib/slub_kunit.c
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 2779c29d9981..9b8a0d754278 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2371,6 +2371,18 @@ config BITS_TEST
>
>           If unsure, say N.
>
> +config SLUB_KUNIT_TEST
> +       tristate "KUnit test for SLUB cache error detection" if !KUNIT_ALL_TESTS
> +       depends on SLUB_DEBUG && KUNIT && !KASAN
> +       default KUNIT_ALL_TESTS
> +       help
> +         This builds SLUB allocator unit test.
> +         Tests SLUB cache debugging functionality.
> +         For more information on KUnit and unit tests in general please refer
> +         to the KUnit documentation in Documentation/dev-tools/kunit/.
> +
> +         If unsure, say N.
> +
>  config TEST_UDELAY
>         tristate "udelay test driver"
>         help
> diff --git a/lib/Makefile b/lib/Makefile
> index b5307d3eec1a..1e59c6714ed8 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -352,5 +352,6 @@ obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
>  obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
>  obj-$(CONFIG_BITS_TEST) += test_bits.o
>  obj-$(CONFIG_CMDLINE_KUNIT_TEST) += cmdline_kunit.o
> +obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o
>
>  obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o
> diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
> new file mode 100644
> index 000000000000..cb9ae9f7e8a6
> --- /dev/null
> +++ b/lib/slub_kunit.c
> @@ -0,0 +1,150 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <kunit/test.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include "../mm/slab.h"
> +
> +static struct kunit_resource resource;
> +static int slab_errors;
> +
> +static void test_clobber_zone(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_alloc", 64, 0,
> +                               SLAB_RED_ZONE, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +
> +       p[64] = 0x12;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +
> +       kmem_cache_free(s, p);
> +       kmem_cache_destroy(s);
> +}
> +
> +static void test_next_pointer(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_next_ptr_free", 64, 0,
> +                               SLAB_POISON, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +       unsigned long tmp;
> +       unsigned long *ptr_addr;
> +
> +       kmem_cache_free(s, p);
> +
> +       ptr_addr = (unsigned long *)(p + s->offset);
> +       tmp = *ptr_addr;
> +       p[s->offset] = 0x12;
> +
> +       /*
> +        * Expecting three errors.
> +        * One for the corrupted freechain and the other one for the wrong
> +        * count of objects in use. The third error is fixing broken cache.
> +        */
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 3, slab_errors);
> +
> +       /*
> +        * Try to repair corrupted freepointer.
> +        * Still expecting two errors. The first for the wrong count
> +        * of objects in use.
> +        * The second error is for fixing broken cache.
> +        */
> +       *ptr_addr = tmp;
> +       slab_errors = 0;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +
> +       /*
> +        * Previous validation repaired the count of objects in use.
> +        * Now expecting no error.
> +        */
> +       slab_errors = 0;
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 0, slab_errors);
> +
> +       kmem_cache_destroy(s);
> +}
> +
> +static void test_first_word(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_1th_word_free", 64, 0,
> +                               SLAB_POISON, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +
> +       kmem_cache_free(s, p);
> +       *p = 0x78;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +
> +       kmem_cache_destroy(s);
> +}
> +
> +static void test_clobber_50th_byte(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_50th_word_free", 64, 0,
> +                               SLAB_POISON, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +
> +       kmem_cache_free(s, p);
> +       p[50] = 0x9a;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +       kmem_cache_destroy(s);
> +}
> +
> +static void test_clobber_redzone_free(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_free", 64, 0,
> +                               SLAB_RED_ZONE, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +
> +       kmem_cache_free(s, p);
> +       p[64] = 0xab;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +       kmem_cache_destroy(s);
> +}
> +
> +static int test_init(struct kunit *test)
> +{
> +       slab_errors = 0;
> +
> +       /* FIXME: remove when CONFIG_KASAN requirement is dropped. */
> +       current->kunit_test = test;

Note, the patch "kunit: support failure from dynamic analysis tools"
is already in -next. It's probably safe to leave this, and send a
follow-up patch later once that kunit patch is in mainline.

> +       kunit_add_named_resource(test, NULL, NULL, &resource,
> +                                       "slab_errors", &slab_errors);
> +       return 0;
> +}
> +
> +static void test_exit(struct kunit *test)
> +{
> +       /* FIXME: remove when CONFIG_KASAN requirement is dropped. */
> +       current->kunit_test = NULL;
> +}
> +
> +static struct kunit_case test_cases[] = {
> +       KUNIT_CASE(test_clobber_zone),
> +       KUNIT_CASE(test_next_pointer),
> +       KUNIT_CASE(test_first_word),
> +       KUNIT_CASE(test_clobber_50th_byte),
> +       KUNIT_CASE(test_clobber_redzone_free),
> +       {}
> +};
> +
> +static struct kunit_suite test_suite = {
> +       .name = "slub_test",
> +       .init = test_init,
> +       .exit = test_exit,
> +       .test_cases = test_cases,
> +};
> +kunit_test_suite(test_suite);
> +
> +MODULE_LICENSE("GPL");
> diff --git a/mm/slab.h b/mm/slab.h
> index 076582f58f68..95cf42eb8396 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -215,6 +215,7 @@ DECLARE_STATIC_KEY_TRUE(slub_debug_enabled);
>  DECLARE_STATIC_KEY_FALSE(slub_debug_enabled);
>  #endif
>  extern void print_tracking(struct kmem_cache *s, void *object);
> +long validate_slab_cache(struct kmem_cache *s);
>  #else
>  static inline void print_tracking(struct kmem_cache *s, void *object)
>  {
> diff --git a/mm/slub.c b/mm/slub.c
> index 3021ce9bf1b3..d7df8841d90a 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -35,6 +35,7 @@
>  #include <linux/prefetch.h>
>  #include <linux/memcontrol.h>
>  #include <linux/random.h>
> +#include <kunit/test.h>
>
>  #include <trace/events/kmem.h>
>
> @@ -447,6 +448,26 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
>  static unsigned long object_map[BITS_TO_LONGS(MAX_OBJS_PER_PAGE)];
>  static DEFINE_SPINLOCK(object_map_lock);
>
> +#if IS_ENABLED(CONFIG_KUNIT)
> +static bool slab_add_kunit_errors(void)
> +{
> +       struct kunit_resource *resource;
> +
> +       if (likely(!current->kunit_test))
> +               return false;
> +
> +       resource = kunit_find_named_resource(current->kunit_test, "slab_errors");
> +       if (!resource)
> +               return false;
> +
> +       (*(int *)resource->data)++;
> +       kunit_put_resource(resource);
> +       return true;
> +}
> +#else
> +static inline bool slab_add_kunit_errors(void) { return false; }
> +#endif
> +
>  /*
>   * Determine a map of object in use on a page.
>   *
> @@ -676,6 +697,9 @@ static void slab_fix(struct kmem_cache *s, char *fmt, ...)
>         struct va_format vaf;
>         va_list args;
>
> +       if (slab_add_kunit_errors())
> +               return;
> +
>         va_start(args, fmt);
>         vaf.fmt = fmt;
>         vaf.va = &args;
> @@ -739,6 +763,9 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
>  void object_err(struct kmem_cache *s, struct page *page,
>                         u8 *object, char *reason)
>  {
> +       if (slab_add_kunit_errors())
> +               return;
> +
>         slab_bug(s, "%s", reason);
>         print_trailer(s, page, object);
>  }
> @@ -749,6 +776,9 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
>         va_list args;
>         char buf[100];
>
> +       if (slab_add_kunit_errors())
> +               return;
> +
>         va_start(args, fmt);
>         vsnprintf(buf, sizeof(buf), fmt, args);
>         va_end(args);
> @@ -798,12 +828,16 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
>         while (end > fault && end[-1] == value)
>                 end--;
>
> +       if (slab_add_kunit_errors())
> +               goto skip_bug_print;
> +
>         slab_bug(s, "%s overwritten", what);
>         pr_err("INFO: 0x%p-0x%p @offset=%tu. First byte 0x%x instead of 0x%x\n",
> -                                       fault, end - 1, fault - addr,
> -                                       fault[0], value);
> +                               fault, end - 1, fault - addr,
> +                               fault[0], value);
>         print_trailer(s, page, object);
>
> +skip_bug_print:
>         restore_bytes(s, what, value, fault, end);
>         return 0;
>  }
> @@ -4650,9 +4684,11 @@ static int validate_slab_node(struct kmem_cache *s,
>                 validate_slab(s, page);
>                 count++;
>         }
> -       if (count != n->nr_partial)
> +       if (count != n->nr_partial) {
>                 pr_err("SLUB %s: %ld partial slabs counted but counter=%ld\n",
>                        s->name, count, n->nr_partial);
> +               slab_add_kunit_errors();
> +       }
>
>         if (!(s->flags & SLAB_STORE_USER))
>                 goto out;
> @@ -4661,16 +4697,18 @@ static int validate_slab_node(struct kmem_cache *s,
>                 validate_slab(s, page);
>                 count++;
>         }
> -       if (count != atomic_long_read(&n->nr_slabs))
> +       if (count != atomic_long_read(&n->nr_slabs)) {
>                 pr_err("SLUB: %s %ld slabs counted but counter=%ld\n",
>                        s->name, count, atomic_long_read(&n->nr_slabs));
> +               slab_add_kunit_errors();
> +       }
>
>  out:
>         spin_unlock_irqrestore(&n->list_lock, flags);
>         return count;
>  }
>
> -static long validate_slab_cache(struct kmem_cache *s)
> +long validate_slab_cache(struct kmem_cache *s)
>  {
>         int node;
>         unsigned long count = 0;
> @@ -4682,6 +4720,8 @@ static long validate_slab_cache(struct kmem_cache *s)
>
>         return count;
>  }
> +EXPORT_SYMBOL(validate_slab_cache);
> +
>  /*
>   * Generate lists of code addresses where slabcache objects are allocated
>   * and freed.
> --
> 2.31.1.272.g89b43f80a5
>
Daniel Latypov April 13, 2021, 9:33 p.m. UTC | #3
On Tue, Apr 13, 2021 at 3:07 AM <glittao@gmail.com> wrote:
>
> From: Oliver Glitta <glittao@gmail.com>
>
> SLUB has resiliency_test() function which is hidden behind #ifdef
> SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody
> runs it. KUnit should be a proper replacement for it.
>
> Try changing byte in redzone after allocation and changing
> pointer to next free node, first byte, 50th byte and redzone
> byte. Check if validation finds errors.
>
> There are several differences from the original resiliency test:
> Tests create own caches with known state instead of corrupting
> shared kmalloc caches.
>
> The corruption of freepointer uses correct offset, the original
> resiliency test got broken with freepointer changes.
>
> Scratch changing random byte test, because it does not have
> meaning in this form where we need deterministic results.
>
> Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.
> Because the test deliberatly modifies non-allocated objects, it depends on

nit: *deliberately

> !KASAN which would have otherwise prevented that.
>
> Use kunit_resource to count errors in cache and silence bug reports.
> Count error whenever slab_bug() or slab_fix() is called or when
> the count of pages is wrong.
>
> Signed-off-by: Oliver Glitta <glittao@gmail.com>

Acked-by: Daniel Latypov <dlatypov@google.com>

Looks good to me!
My one minor suggestion: perhaps let's log a summary of the error or
the func name in slab_add_kunit_errors().

> ---
> Changes since v3
>
> Use kunit_resource to silence bug reports and count errors suggested by
> Marco Elver.
> Make the test depends on !KASAN thanks to report from the kernel test robot.
>
> Changes since v2
>
> Use bit operation & instead of logical && as reported by kernel test
> robot and Dan Carpenter
>
> Changes since v1
>
> Conversion from kselftest to KUnit test suggested by Marco Elver.
> Error silencing.
> Error counting improvements.
>  lib/Kconfig.debug |  12 ++++
>  lib/Makefile      |   1 +
>  lib/slub_kunit.c  | 150 ++++++++++++++++++++++++++++++++++++++++++++++
>  mm/slab.h         |   1 +
>  mm/slub.c         |  50 ++++++++++++++--
>  5 files changed, 209 insertions(+), 5 deletions(-)
>  create mode 100644 lib/slub_kunit.c
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 2779c29d9981..9b8a0d754278 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2371,6 +2371,18 @@ config BITS_TEST
>
>           If unsure, say N.
>
> +config SLUB_KUNIT_TEST
> +       tristate "KUnit test for SLUB cache error detection" if !KUNIT_ALL_TESTS
> +       depends on SLUB_DEBUG && KUNIT && !KASAN
> +       default KUNIT_ALL_TESTS
> +       help
> +         This builds SLUB allocator unit test.
> +         Tests SLUB cache debugging functionality.
> +         For more information on KUnit and unit tests in general please refer
> +         to the KUnit documentation in Documentation/dev-tools/kunit/.
> +
> +         If unsure, say N.
> +
>  config TEST_UDELAY
>         tristate "udelay test driver"
>         help
> diff --git a/lib/Makefile b/lib/Makefile
> index b5307d3eec1a..1e59c6714ed8 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -352,5 +352,6 @@ obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
>  obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
>  obj-$(CONFIG_BITS_TEST) += test_bits.o
>  obj-$(CONFIG_CMDLINE_KUNIT_TEST) += cmdline_kunit.o
> +obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o
>
>  obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o
> diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
> new file mode 100644
> index 000000000000..cb9ae9f7e8a6
> --- /dev/null
> +++ b/lib/slub_kunit.c
> @@ -0,0 +1,150 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <kunit/test.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include "../mm/slab.h"
> +
> +static struct kunit_resource resource;
> +static int slab_errors;
> +
> +static void test_clobber_zone(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_alloc", 64, 0,
> +                               SLAB_RED_ZONE, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +
> +       p[64] = 0x12;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +
> +       kmem_cache_free(s, p);
> +       kmem_cache_destroy(s);

Might not be worth doing for now:
I see kmem_cache_destroy() has a `if (err) { pr_err(...); dump_stack(); }` call.
Does it make sense to cause that to fail the test?

I see it's defined in mm/slab_common.c, so we might not want to touch
that in this patch.

> +}
> +
> +static void test_next_pointer(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_next_ptr_free", 64, 0,
> +                               SLAB_POISON, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +       unsigned long tmp;
> +       unsigned long *ptr_addr;
> +
> +       kmem_cache_free(s, p);
> +
> +       ptr_addr = (unsigned long *)(p + s->offset);
> +       tmp = *ptr_addr;
> +       p[s->offset] = 0x12;
> +

I really like this test!
I think it'll be a good example to point to wrt handle mutating state
in tests (clear comments, using whitespace to break up steps, setting
up clear EXPECT calls, etc.)

> +       /*
> +        * Expecting three errors.
> +        * One for the corrupted freechain and the other one for the wrong
> +        * count of objects in use. The third error is fixing broken cache.
> +        */
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 3, slab_errors);
> +
> +       /*
> +        * Try to repair corrupted freepointer.
> +        * Still expecting two errors. The first for the wrong count
> +        * of objects in use.
> +        * The second error is for fixing broken cache.
> +        */
> +       *ptr_addr = tmp;
> +       slab_errors = 0;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +
> +       /*
> +        * Previous validation repaired the count of objects in use.
> +        * Now expecting no error.
> +        */
> +       slab_errors = 0;
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 0, slab_errors);
> +
> +       kmem_cache_destroy(s);
> +}
> +
> +static void test_first_word(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_1th_word_free", 64, 0,
> +                               SLAB_POISON, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +
> +       kmem_cache_free(s, p);
> +       *p = 0x78;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +
> +       kmem_cache_destroy(s);
> +}
> +
> +static void test_clobber_50th_byte(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_50th_word_free", 64, 0,
> +                               SLAB_POISON, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +
> +       kmem_cache_free(s, p);
> +       p[50] = 0x9a;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +       kmem_cache_destroy(s);
> +}
> +
> +static void test_clobber_redzone_free(struct kunit *test)
> +{
> +       struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_free", 64, 0,
> +                               SLAB_RED_ZONE, NULL);
> +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +
> +       kmem_cache_free(s, p);
> +       p[64] = 0xab;
> +
> +       validate_slab_cache(s);
> +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> +       kmem_cache_destroy(s);
> +}
> +
> +static int test_init(struct kunit *test)
> +{
> +       slab_errors = 0;
> +
> +       /* FIXME: remove when CONFIG_KASAN requirement is dropped. */
> +       current->kunit_test = test;
> +
> +       kunit_add_named_resource(test, NULL, NULL, &resource,
> +                                       "slab_errors", &slab_errors);
> +       return 0;
> +}
> +
> +static void test_exit(struct kunit *test)
> +{
> +       /* FIXME: remove when CONFIG_KASAN requirement is dropped. */
> +       current->kunit_test = NULL;
> +}
> +
> +static struct kunit_case test_cases[] = {
> +       KUNIT_CASE(test_clobber_zone),
> +       KUNIT_CASE(test_next_pointer),
> +       KUNIT_CASE(test_first_word),
> +       KUNIT_CASE(test_clobber_50th_byte),
> +       KUNIT_CASE(test_clobber_redzone_free),
> +       {}
> +};
> +
> +static struct kunit_suite test_suite = {
> +       .name = "slub_test",
> +       .init = test_init,
> +       .exit = test_exit,
> +       .test_cases = test_cases,
> +};
> +kunit_test_suite(test_suite);
> +
> +MODULE_LICENSE("GPL");
> diff --git a/mm/slab.h b/mm/slab.h
> index 076582f58f68..95cf42eb8396 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -215,6 +215,7 @@ DECLARE_STATIC_KEY_TRUE(slub_debug_enabled);
>  DECLARE_STATIC_KEY_FALSE(slub_debug_enabled);
>  #endif
>  extern void print_tracking(struct kmem_cache *s, void *object);
> +long validate_slab_cache(struct kmem_cache *s);
>  #else
>  static inline void print_tracking(struct kmem_cache *s, void *object)
>  {
> diff --git a/mm/slub.c b/mm/slub.c
> index 3021ce9bf1b3..d7df8841d90a 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -35,6 +35,7 @@
>  #include <linux/prefetch.h>
>  #include <linux/memcontrol.h>
>  #include <linux/random.h>
> +#include <kunit/test.h>
>
>  #include <trace/events/kmem.h>
>
> @@ -447,6 +448,26 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
>  static unsigned long object_map[BITS_TO_LONGS(MAX_OBJS_PER_PAGE)];
>  static DEFINE_SPINLOCK(object_map_lock);
>
> +#if IS_ENABLED(CONFIG_KUNIT)
> +static bool slab_add_kunit_errors(void)
> +{
> +       struct kunit_resource *resource;
> +
> +       if (likely(!current->kunit_test))
> +               return false;
> +
> +       resource = kunit_find_named_resource(current->kunit_test, "slab_errors");
> +       if (!resource)
> +               return false;
> +
> +       (*(int *)resource->data)++;
> +       kunit_put_resource(resource);
> +       return true;
> +}
> +#else
> +static inline bool slab_add_kunit_errors(void) { return false; }
> +#endif
> +
>  /*
>   * Determine a map of object in use on a page.
>   *
> @@ -676,6 +697,9 @@ static void slab_fix(struct kmem_cache *s, char *fmt, ...)
>         struct va_format vaf;
>         va_list args;
>
> +       if (slab_add_kunit_errors())
> +               return;
> +
>         va_start(args, fmt);
>         vaf.fmt = fmt;
>         vaf.va = &args;
> @@ -739,6 +763,9 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
>  void object_err(struct kmem_cache *s, struct page *page,
>                         u8 *object, char *reason)
>  {
> +       if (slab_add_kunit_errors())
> +               return;
> +
>         slab_bug(s, "%s", reason);

Would it be a good idea for us to log the error text in slab_add_kunit_errors()?
Otherwise we could end up with getting the same error count but from
an unexpected set of code paths.

Boils down to using this macro
  kunit_info(current->kunit_test, "%s", reason);

Perhaps we could get away with just duplicating (a subset of) what
we'd pass into slab_bug(), i.e.
  if (slab_add_kunit_errors("%s", reason)) return;
  if (slab_add_kunit_errors("%s overwritten", what) return;
If the string we're printing is too annoying to duplicate, can get
away with just using __func__ as well.

Or a more messy alternative would be to add some #if'd code in
slab_bug(), but I don't know if that's as good of an idea.

>         print_trailer(s, page, object);
>  }
> @@ -749,6 +776,9 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
>         va_list args;
>         char buf[100];
>
> +       if (slab_add_kunit_errors())
> +               return;
> +
>         va_start(args, fmt);
>         vsnprintf(buf, sizeof(buf), fmt, args);
>         va_end(args);
> @@ -798,12 +828,16 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
>         while (end > fault && end[-1] == value)
>                 end--;
>
> +       if (slab_add_kunit_errors())
> +               goto skip_bug_print;
> +
>         slab_bug(s, "%s overwritten", what);
>         pr_err("INFO: 0x%p-0x%p @offset=%tu. First byte 0x%x instead of 0x%x\n",
> -                                       fault, end - 1, fault - addr,
> -                                       fault[0], value);
> +                               fault, end - 1, fault - addr,
> +                               fault[0], value);
>         print_trailer(s, page, object);
>
> +skip_bug_print:
>         restore_bytes(s, what, value, fault, end);
>         return 0;
>  }
> @@ -4650,9 +4684,11 @@ static int validate_slab_node(struct kmem_cache *s,
>                 validate_slab(s, page);
>                 count++;
>         }
> -       if (count != n->nr_partial)
> +       if (count != n->nr_partial) {
>                 pr_err("SLUB %s: %ld partial slabs counted but counter=%ld\n",
>                        s->name, count, n->nr_partial);
> +               slab_add_kunit_errors();
> +       }
>
>         if (!(s->flags & SLAB_STORE_USER))
>                 goto out;
> @@ -4661,16 +4697,18 @@ static int validate_slab_node(struct kmem_cache *s,
>                 validate_slab(s, page);
>                 count++;
>         }
> -       if (count != atomic_long_read(&n->nr_slabs))
> +       if (count != atomic_long_read(&n->nr_slabs)) {
>                 pr_err("SLUB: %s %ld slabs counted but counter=%ld\n",
>                        s->name, count, atomic_long_read(&n->nr_slabs));
> +               slab_add_kunit_errors();
> +       }
>
>  out:
>         spin_unlock_irqrestore(&n->list_lock, flags);
>         return count;
>  }
>
> -static long validate_slab_cache(struct kmem_cache *s)
> +long validate_slab_cache(struct kmem_cache *s)
>  {
>         int node;
>         unsigned long count = 0;
> @@ -4682,6 +4720,8 @@ static long validate_slab_cache(struct kmem_cache *s)
>
>         return count;
>  }
> +EXPORT_SYMBOL(validate_slab_cache);
> +
>  /*
>   * Generate lists of code addresses where slabcache objects are allocated
>   * and freed.
> --
> 2.31.1.272.g89b43f80a5
>
Oliver Glitta April 15, 2021, 10:10 a.m. UTC | #4
ut 13. 4. 2021 o 15:54 Marco Elver <elver@google.com> napísal(a):
>
> On Tue, 13 Apr 2021 at 12:07, <glittao@gmail.com> wrote:
> > From: Oliver Glitta <glittao@gmail.com>
> >
> > SLUB has resiliency_test() function which is hidden behind #ifdef
> > SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody
> > runs it. KUnit should be a proper replacement for it.
> >
> > Try changing byte in redzone after allocation and changing
> > pointer to next free node, first byte, 50th byte and redzone
> > byte. Check if validation finds errors.
> >
> > There are several differences from the original resiliency test:
> > Tests create own caches with known state instead of corrupting
> > shared kmalloc caches.
> >
> > The corruption of freepointer uses correct offset, the original
> > resiliency test got broken with freepointer changes.
> >
> > Scratch changing random byte test, because it does not have
> > meaning in this form where we need deterministic results.
> >
> > Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.
> > Because the test deliberatly modifies non-allocated objects, it depends on
> > !KASAN which would have otherwise prevented that.
>
> Hmm, did the test fail with KASAN? Is it possible to skip the tests
> and still run a subset of tests with KASAN? It'd be nice if we could
> run some of these tests with KASAN as well.
>
> > Use kunit_resource to count errors in cache and silence bug reports.
> > Count error whenever slab_bug() or slab_fix() is called or when
> > the count of pages is wrong.
> >
> > Signed-off-by: Oliver Glitta <glittao@gmail.com>
>
> Reviewed-by: Marco Elver <elver@google.com>
>

Thank you.

> Thanks, this all looks good to me. But perhaps do test what works with
> KASAN, to see if you need the !KASAN constraint for all cases.

I tried to run tests with KASAN functionality disabled with function
kasan_disable_current() and three of the tests failed with wrong
errors counts.
So I add the !KASAN constraint for all tests, because the merge window
is coming, we want to know if this version is stable and without other
mistakes.
We will take a closer look at that in the follow-up patch.

>
> > ---
> > Changes since v3
> >
> > Use kunit_resource to silence bug reports and count errors suggested by
> > Marco Elver.
> > Make the test depends on !KASAN thanks to report from the kernel test robot.
> >
> > Changes since v2
> >
> > Use bit operation & instead of logical && as reported by kernel test
> > robot and Dan Carpenter
> >
> > Changes since v1
> >
> > Conversion from kselftest to KUnit test suggested by Marco Elver.
> > Error silencing.
> > Error counting improvements.
> >  lib/Kconfig.debug |  12 ++++
> >  lib/Makefile      |   1 +
> >  lib/slub_kunit.c  | 150 ++++++++++++++++++++++++++++++++++++++++++++++
> >  mm/slab.h         |   1 +
> >  mm/slub.c         |  50 ++++++++++++++--
> >  5 files changed, 209 insertions(+), 5 deletions(-)
> >  create mode 100644 lib/slub_kunit.c
> >
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 2779c29d9981..9b8a0d754278 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -2371,6 +2371,18 @@ config BITS_TEST
> >
> >           If unsure, say N.
> >
> > +config SLUB_KUNIT_TEST
> > +       tristate "KUnit test for SLUB cache error detection" if !KUNIT_ALL_TESTS
> > +       depends on SLUB_DEBUG && KUNIT && !KASAN
> > +       default KUNIT_ALL_TESTS
> > +       help
> > +         This builds SLUB allocator unit test.
> > +         Tests SLUB cache debugging functionality.
> > +         For more information on KUnit and unit tests in general please refer
> > +         to the KUnit documentation in Documentation/dev-tools/kunit/.
> > +
> > +         If unsure, say N.
> > +
> >  config TEST_UDELAY
> >         tristate "udelay test driver"
> >         help
> > diff --git a/lib/Makefile b/lib/Makefile
> > index b5307d3eec1a..1e59c6714ed8 100644
> > --- a/lib/Makefile
> > +++ b/lib/Makefile
> > @@ -352,5 +352,6 @@ obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
> >  obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
> >  obj-$(CONFIG_BITS_TEST) += test_bits.o
> >  obj-$(CONFIG_CMDLINE_KUNIT_TEST) += cmdline_kunit.o
> > +obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o
> >
> >  obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o
> > diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
> > new file mode 100644
> > index 000000000000..cb9ae9f7e8a6
> > --- /dev/null
> > +++ b/lib/slub_kunit.c
> > @@ -0,0 +1,150 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <kunit/test.h>
> > +#include <linux/mm.h>
> > +#include <linux/slab.h>
> > +#include <linux/module.h>
> > +#include <linux/kernel.h>
> > +#include "../mm/slab.h"
> > +
> > +static struct kunit_resource resource;
> > +static int slab_errors;
> > +
> > +static void test_clobber_zone(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_alloc", 64, 0,
> > +                               SLAB_RED_ZONE, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +
> > +       p[64] = 0x12;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +
> > +       kmem_cache_free(s, p);
> > +       kmem_cache_destroy(s);
> > +}
> > +
> > +static void test_next_pointer(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_next_ptr_free", 64, 0,
> > +                               SLAB_POISON, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +       unsigned long tmp;
> > +       unsigned long *ptr_addr;
> > +
> > +       kmem_cache_free(s, p);
> > +
> > +       ptr_addr = (unsigned long *)(p + s->offset);
> > +       tmp = *ptr_addr;
> > +       p[s->offset] = 0x12;
> > +
> > +       /*
> > +        * Expecting three errors.
> > +        * One for the corrupted freechain and the other one for the wrong
> > +        * count of objects in use. The third error is fixing broken cache.
> > +        */
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 3, slab_errors);
> > +
> > +       /*
> > +        * Try to repair corrupted freepointer.
> > +        * Still expecting two errors. The first for the wrong count
> > +        * of objects in use.
> > +        * The second error is for fixing broken cache.
> > +        */
> > +       *ptr_addr = tmp;
> > +       slab_errors = 0;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +
> > +       /*
> > +        * Previous validation repaired the count of objects in use.
> > +        * Now expecting no error.
> > +        */
> > +       slab_errors = 0;
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 0, slab_errors);
> > +
> > +       kmem_cache_destroy(s);
> > +}
> > +
> > +static void test_first_word(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_1th_word_free", 64, 0,
> > +                               SLAB_POISON, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +
> > +       kmem_cache_free(s, p);
> > +       *p = 0x78;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +
> > +       kmem_cache_destroy(s);
> > +}
> > +
> > +static void test_clobber_50th_byte(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_50th_word_free", 64, 0,
> > +                               SLAB_POISON, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +
> > +       kmem_cache_free(s, p);
> > +       p[50] = 0x9a;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +       kmem_cache_destroy(s);
> > +}
> > +
> > +static void test_clobber_redzone_free(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_free", 64, 0,
> > +                               SLAB_RED_ZONE, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +
> > +       kmem_cache_free(s, p);
> > +       p[64] = 0xab;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +       kmem_cache_destroy(s);
> > +}
> > +
> > +static int test_init(struct kunit *test)
> > +{
> > +       slab_errors = 0;
> > +
> > +       /* FIXME: remove when CONFIG_KASAN requirement is dropped. */
> > +       current->kunit_test = test;
>
> Note, the patch "kunit: support failure from dynamic analysis tools"
> is already in -next. It's probably safe to leave this, and send a
> follow-up patch later once that kunit patch is in mainline.
>
> > +       kunit_add_named_resource(test, NULL, NULL, &resource,
> > +                                       "slab_errors", &slab_errors);
> > +       return 0;
> > +}
> > +
> > +static void test_exit(struct kunit *test)
> > +{
> > +       /* FIXME: remove when CONFIG_KASAN requirement is dropped. */
> > +       current->kunit_test = NULL;
> > +}
> > +
> > +static struct kunit_case test_cases[] = {
> > +       KUNIT_CASE(test_clobber_zone),
> > +       KUNIT_CASE(test_next_pointer),
> > +       KUNIT_CASE(test_first_word),
> > +       KUNIT_CASE(test_clobber_50th_byte),
> > +       KUNIT_CASE(test_clobber_redzone_free),
> > +       {}
> > +};
> > +
> > +static struct kunit_suite test_suite = {
> > +       .name = "slub_test",
> > +       .init = test_init,
> > +       .exit = test_exit,
> > +       .test_cases = test_cases,
> > +};
> > +kunit_test_suite(test_suite);
> > +
> > +MODULE_LICENSE("GPL");
> > diff --git a/mm/slab.h b/mm/slab.h
> > index 076582f58f68..95cf42eb8396 100644
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -215,6 +215,7 @@ DECLARE_STATIC_KEY_TRUE(slub_debug_enabled);
> >  DECLARE_STATIC_KEY_FALSE(slub_debug_enabled);
> >  #endif
> >  extern void print_tracking(struct kmem_cache *s, void *object);
> > +long validate_slab_cache(struct kmem_cache *s);
> >  #else
> >  static inline void print_tracking(struct kmem_cache *s, void *object)
> >  {
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 3021ce9bf1b3..d7df8841d90a 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -35,6 +35,7 @@
> >  #include <linux/prefetch.h>
> >  #include <linux/memcontrol.h>
> >  #include <linux/random.h>
> > +#include <kunit/test.h>
> >
> >  #include <trace/events/kmem.h>
> >
> > @@ -447,6 +448,26 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
> >  static unsigned long object_map[BITS_TO_LONGS(MAX_OBJS_PER_PAGE)];
> >  static DEFINE_SPINLOCK(object_map_lock);
> >
> > +#if IS_ENABLED(CONFIG_KUNIT)
> > +static bool slab_add_kunit_errors(void)
> > +{
> > +       struct kunit_resource *resource;
> > +
> > +       if (likely(!current->kunit_test))
> > +               return false;
> > +
> > +       resource = kunit_find_named_resource(current->kunit_test, "slab_errors");
> > +       if (!resource)
> > +               return false;
> > +
> > +       (*(int *)resource->data)++;
> > +       kunit_put_resource(resource);
> > +       return true;
> > +}
> > +#else
> > +static inline bool slab_add_kunit_errors(void) { return false; }
> > +#endif
> > +
> >  /*
> >   * Determine a map of object in use on a page.
> >   *
> > @@ -676,6 +697,9 @@ static void slab_fix(struct kmem_cache *s, char *fmt, ...)
> >         struct va_format vaf;
> >         va_list args;
> >
> > +       if (slab_add_kunit_errors())
> > +               return;
> > +
> >         va_start(args, fmt);
> >         vaf.fmt = fmt;
> >         vaf.va = &args;
> > @@ -739,6 +763,9 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
> >  void object_err(struct kmem_cache *s, struct page *page,
> >                         u8 *object, char *reason)
> >  {
> > +       if (slab_add_kunit_errors())
> > +               return;
> > +
> >         slab_bug(s, "%s", reason);
> >         print_trailer(s, page, object);
> >  }
> > @@ -749,6 +776,9 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> >         va_list args;
> >         char buf[100];
> >
> > +       if (slab_add_kunit_errors())
> > +               return;
> > +
> >         va_start(args, fmt);
> >         vsnprintf(buf, sizeof(buf), fmt, args);
> >         va_end(args);
> > @@ -798,12 +828,16 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
> >         while (end > fault && end[-1] == value)
> >                 end--;
> >
> > +       if (slab_add_kunit_errors())
> > +               goto skip_bug_print;
> > +
> >         slab_bug(s, "%s overwritten", what);
> >         pr_err("INFO: 0x%p-0x%p @offset=%tu. First byte 0x%x instead of 0x%x\n",
> > -                                       fault, end - 1, fault - addr,
> > -                                       fault[0], value);
> > +                               fault, end - 1, fault - addr,
> > +                               fault[0], value);
> >         print_trailer(s, page, object);
> >
> > +skip_bug_print:
> >         restore_bytes(s, what, value, fault, end);
> >         return 0;
> >  }
> > @@ -4650,9 +4684,11 @@ static int validate_slab_node(struct kmem_cache *s,
> >                 validate_slab(s, page);
> >                 count++;
> >         }
> > -       if (count != n->nr_partial)
> > +       if (count != n->nr_partial) {
> >                 pr_err("SLUB %s: %ld partial slabs counted but counter=%ld\n",
> >                        s->name, count, n->nr_partial);
> > +               slab_add_kunit_errors();
> > +       }
> >
> >         if (!(s->flags & SLAB_STORE_USER))
> >                 goto out;
> > @@ -4661,16 +4697,18 @@ static int validate_slab_node(struct kmem_cache *s,
> >                 validate_slab(s, page);
> >                 count++;
> >         }
> > -       if (count != atomic_long_read(&n->nr_slabs))
> > +       if (count != atomic_long_read(&n->nr_slabs)) {
> >                 pr_err("SLUB: %s %ld slabs counted but counter=%ld\n",
> >                        s->name, count, atomic_long_read(&n->nr_slabs));
> > +               slab_add_kunit_errors();
> > +       }
> >
> >  out:
> >         spin_unlock_irqrestore(&n->list_lock, flags);
> >         return count;
> >  }
> >
> > -static long validate_slab_cache(struct kmem_cache *s)
> > +long validate_slab_cache(struct kmem_cache *s)
> >  {
> >         int node;
> >         unsigned long count = 0;
> > @@ -4682,6 +4720,8 @@ static long validate_slab_cache(struct kmem_cache *s)
> >
> >         return count;
> >  }
> > +EXPORT_SYMBOL(validate_slab_cache);
> > +
> >  /*
> >   * Generate lists of code addresses where slabcache objects are allocated
> >   * and freed.
> > --
> > 2.31.1.272.g89b43f80a5
> >
Oliver Glitta April 15, 2021, 10:11 a.m. UTC | #5
ut 13. 4. 2021 o 23:33 Daniel Latypov <dlatypov@google.com> napísal(a):
>
> On Tue, Apr 13, 2021 at 3:07 AM <glittao@gmail.com> wrote:
> >
> > From: Oliver Glitta <glittao@gmail.com>
> >
> > SLUB has resiliency_test() function which is hidden behind #ifdef
> > SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody
> > runs it. KUnit should be a proper replacement for it.
> >
> > Try changing byte in redzone after allocation and changing
> > pointer to next free node, first byte, 50th byte and redzone
> > byte. Check if validation finds errors.
> >
> > There are several differences from the original resiliency test:
> > Tests create own caches with known state instead of corrupting
> > shared kmalloc caches.
> >
> > The corruption of freepointer uses correct offset, the original
> > resiliency test got broken with freepointer changes.
> >
> > Scratch changing random byte test, because it does not have
> > meaning in this form where we need deterministic results.
> >
> > Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.
> > Because the test deliberatly modifies non-allocated objects, it depends on
>
> nit: *deliberately
>
> > !KASAN which would have otherwise prevented that.
> >
> > Use kunit_resource to count errors in cache and silence bug reports.
> > Count error whenever slab_bug() or slab_fix() is called or when
> > the count of pages is wrong.
> >
> > Signed-off-by: Oliver Glitta <glittao@gmail.com>
>
> Acked-by: Daniel Latypov <dlatypov@google.com>
>

Thank you.

> Looks good to me!
> My one minor suggestion: perhaps let's log a summary of the error or
> the func name in slab_add_kunit_errors().
>

That is a good suggestion, but now we want to know if this version is stable.
We will take a look at that in the follow-up patch.

> > ---
> > Changes since v3
> >
> > Use kunit_resource to silence bug reports and count errors suggested by
> > Marco Elver.
> > Make the test depends on !KASAN thanks to report from the kernel test robot.
> >
> > Changes since v2
> >
> > Use bit operation & instead of logical && as reported by kernel test
> > robot and Dan Carpenter
> >
> > Changes since v1
> >
> > Conversion from kselftest to KUnit test suggested by Marco Elver.
> > Error silencing.
> > Error counting improvements.
> >  lib/Kconfig.debug |  12 ++++
> >  lib/Makefile      |   1 +
> >  lib/slub_kunit.c  | 150 ++++++++++++++++++++++++++++++++++++++++++++++
> >  mm/slab.h         |   1 +
> >  mm/slub.c         |  50 ++++++++++++++--
> >  5 files changed, 209 insertions(+), 5 deletions(-)
> >  create mode 100644 lib/slub_kunit.c
> >
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 2779c29d9981..9b8a0d754278 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -2371,6 +2371,18 @@ config BITS_TEST
> >
> >           If unsure, say N.
> >
> > +config SLUB_KUNIT_TEST
> > +       tristate "KUnit test for SLUB cache error detection" if !KUNIT_ALL_TESTS
> > +       depends on SLUB_DEBUG && KUNIT && !KASAN
> > +       default KUNIT_ALL_TESTS
> > +       help
> > +         This builds SLUB allocator unit test.
> > +         Tests SLUB cache debugging functionality.
> > +         For more information on KUnit and unit tests in general please refer
> > +         to the KUnit documentation in Documentation/dev-tools/kunit/.
> > +
> > +         If unsure, say N.
> > +
> >  config TEST_UDELAY
> >         tristate "udelay test driver"
> >         help
> > diff --git a/lib/Makefile b/lib/Makefile
> > index b5307d3eec1a..1e59c6714ed8 100644
> > --- a/lib/Makefile
> > +++ b/lib/Makefile
> > @@ -352,5 +352,6 @@ obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
> >  obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
> >  obj-$(CONFIG_BITS_TEST) += test_bits.o
> >  obj-$(CONFIG_CMDLINE_KUNIT_TEST) += cmdline_kunit.o
> > +obj-$(CONFIG_SLUB_KUNIT_TEST) += slub_kunit.o
> >
> >  obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o
> > diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
> > new file mode 100644
> > index 000000000000..cb9ae9f7e8a6
> > --- /dev/null
> > +++ b/lib/slub_kunit.c
> > @@ -0,0 +1,150 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <kunit/test.h>
> > +#include <linux/mm.h>
> > +#include <linux/slab.h>
> > +#include <linux/module.h>
> > +#include <linux/kernel.h>
> > +#include "../mm/slab.h"
> > +
> > +static struct kunit_resource resource;
> > +static int slab_errors;
> > +
> > +static void test_clobber_zone(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_alloc", 64, 0,
> > +                               SLAB_RED_ZONE, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +
> > +       p[64] = 0x12;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +
> > +       kmem_cache_free(s, p);
> > +       kmem_cache_destroy(s);
>
> Might not be worth doing for now:
> I see kmem_cache_destroy() has a `if (err) { pr_err(...); dump_stack(); }` call.
> Does it make sense to cause that to fail the test?
>
> I see it's defined in mm/slab_common.c, so we might not want to touch
> that in this patch.
>
> > +}
> > +
> > +static void test_next_pointer(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_next_ptr_free", 64, 0,
> > +                               SLAB_POISON, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +       unsigned long tmp;
> > +       unsigned long *ptr_addr;
> > +
> > +       kmem_cache_free(s, p);
> > +
> > +       ptr_addr = (unsigned long *)(p + s->offset);
> > +       tmp = *ptr_addr;
> > +       p[s->offset] = 0x12;
> > +
>
> I really like this test!
> I think it'll be a good example to point to wrt handle mutating state
> in tests (clear comments, using whitespace to break up steps, setting
> up clear EXPECT calls, etc.)
>
> > +       /*
> > +        * Expecting three errors.
> > +        * One for the corrupted freechain and the other one for the wrong
> > +        * count of objects in use. The third error is fixing broken cache.
> > +        */
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 3, slab_errors);
> > +
> > +       /*
> > +        * Try to repair corrupted freepointer.
> > +        * Still expecting two errors. The first for the wrong count
> > +        * of objects in use.
> > +        * The second error is for fixing broken cache.
> > +        */
> > +       *ptr_addr = tmp;
> > +       slab_errors = 0;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +
> > +       /*
> > +        * Previous validation repaired the count of objects in use.
> > +        * Now expecting no error.
> > +        */
> > +       slab_errors = 0;
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 0, slab_errors);
> > +
> > +       kmem_cache_destroy(s);
> > +}
> > +
> > +static void test_first_word(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_1th_word_free", 64, 0,
> > +                               SLAB_POISON, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +
> > +       kmem_cache_free(s, p);
> > +       *p = 0x78;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +
> > +       kmem_cache_destroy(s);
> > +}
> > +
> > +static void test_clobber_50th_byte(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_50th_word_free", 64, 0,
> > +                               SLAB_POISON, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +
> > +       kmem_cache_free(s, p);
> > +       p[50] = 0x9a;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +       kmem_cache_destroy(s);
> > +}
> > +
> > +static void test_clobber_redzone_free(struct kunit *test)
> > +{
> > +       struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_free", 64, 0,
> > +                               SLAB_RED_ZONE, NULL);
> > +       u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> > +
> > +       kmem_cache_free(s, p);
> > +       p[64] = 0xab;
> > +
> > +       validate_slab_cache(s);
> > +       KUNIT_EXPECT_EQ(test, 2, slab_errors);
> > +       kmem_cache_destroy(s);
> > +}
> > +
> > +static int test_init(struct kunit *test)
> > +{
> > +       slab_errors = 0;
> > +
> > +       /* FIXME: remove when CONFIG_KASAN requirement is dropped. */
> > +       current->kunit_test = test;
> > +
> > +       kunit_add_named_resource(test, NULL, NULL, &resource,
> > +                                       "slab_errors", &slab_errors);
> > +       return 0;
> > +}
> > +
> > +static void test_exit(struct kunit *test)
> > +{
> > +       /* FIXME: remove when CONFIG_KASAN requirement is dropped. */
> > +       current->kunit_test = NULL;
> > +}
> > +
> > +static struct kunit_case test_cases[] = {
> > +       KUNIT_CASE(test_clobber_zone),
> > +       KUNIT_CASE(test_next_pointer),
> > +       KUNIT_CASE(test_first_word),
> > +       KUNIT_CASE(test_clobber_50th_byte),
> > +       KUNIT_CASE(test_clobber_redzone_free),
> > +       {}
> > +};
> > +
> > +static struct kunit_suite test_suite = {
> > +       .name = "slub_test",
> > +       .init = test_init,
> > +       .exit = test_exit,
> > +       .test_cases = test_cases,
> > +};
> > +kunit_test_suite(test_suite);
> > +
> > +MODULE_LICENSE("GPL");
> > diff --git a/mm/slab.h b/mm/slab.h
> > index 076582f58f68..95cf42eb8396 100644
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -215,6 +215,7 @@ DECLARE_STATIC_KEY_TRUE(slub_debug_enabled);
> >  DECLARE_STATIC_KEY_FALSE(slub_debug_enabled);
> >  #endif
> >  extern void print_tracking(struct kmem_cache *s, void *object);
> > +long validate_slab_cache(struct kmem_cache *s);
> >  #else
> >  static inline void print_tracking(struct kmem_cache *s, void *object)
> >  {
> > diff --git a/mm/slub.c b/mm/slub.c
> > index 3021ce9bf1b3..d7df8841d90a 100644
> > --- a/mm/slub.c
> > +++ b/mm/slub.c
> > @@ -35,6 +35,7 @@
> >  #include <linux/prefetch.h>
> >  #include <linux/memcontrol.h>
> >  #include <linux/random.h>
> > +#include <kunit/test.h>
> >
> >  #include <trace/events/kmem.h>
> >
> > @@ -447,6 +448,26 @@ static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page,
> >  static unsigned long object_map[BITS_TO_LONGS(MAX_OBJS_PER_PAGE)];
> >  static DEFINE_SPINLOCK(object_map_lock);
> >
> > +#if IS_ENABLED(CONFIG_KUNIT)
> > +static bool slab_add_kunit_errors(void)
> > +{
> > +       struct kunit_resource *resource;
> > +
> > +       if (likely(!current->kunit_test))
> > +               return false;
> > +
> > +       resource = kunit_find_named_resource(current->kunit_test, "slab_errors");
> > +       if (!resource)
> > +               return false;
> > +
> > +       (*(int *)resource->data)++;
> > +       kunit_put_resource(resource);
> > +       return true;
> > +}
> > +#else
> > +static inline bool slab_add_kunit_errors(void) { return false; }
> > +#endif
> > +
> >  /*
> >   * Determine a map of object in use on a page.
> >   *
> > @@ -676,6 +697,9 @@ static void slab_fix(struct kmem_cache *s, char *fmt, ...)
> >         struct va_format vaf;
> >         va_list args;
> >
> > +       if (slab_add_kunit_errors())
> > +               return;
> > +
> >         va_start(args, fmt);
> >         vaf.fmt = fmt;
> >         vaf.va = &args;
> > @@ -739,6 +763,9 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
> >  void object_err(struct kmem_cache *s, struct page *page,
> >                         u8 *object, char *reason)
> >  {
> > +       if (slab_add_kunit_errors())
> > +               return;
> > +
> >         slab_bug(s, "%s", reason);
>
> Would it be a good idea for us to log the error text in slab_add_kunit_errors()?
> Otherwise we could end up with getting the same error count but from
> an unexpected set of code paths.
>
> Boils down to using this macro
>   kunit_info(current->kunit_test, "%s", reason);
>
> Perhaps we could get away with just duplicating (a subset of) what
> we'd pass into slab_bug(), i.e.
>   if (slab_add_kunit_errors("%s", reason)) return;
>   if (slab_add_kunit_errors("%s overwritten", what) return;
> If the string we're printing is too annoying to duplicate, can get
> away with just using __func__ as well.
>
> Or a more messy alternative would be to add some #if'd code in
> slab_bug(), but I don't know if that's as good of an idea.
>
> >         print_trailer(s, page, object);
> >  }
> > @@ -749,6 +776,9 @@ static __printf(3, 4) void slab_err(struct kmem_cache *s, struct page *page,
> >         va_list args;
> >         char buf[100];
> >
> > +       if (slab_add_kunit_errors())
> > +               return;
> > +
> >         va_start(args, fmt);
> >         vsnprintf(buf, sizeof(buf), fmt, args);
> >         va_end(args);
> > @@ -798,12 +828,16 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
> >         while (end > fault && end[-1] == value)
> >                 end--;
> >
> > +       if (slab_add_kunit_errors())
> > +               goto skip_bug_print;
> > +
> >         slab_bug(s, "%s overwritten", what);
> >         pr_err("INFO: 0x%p-0x%p @offset=%tu. First byte 0x%x instead of 0x%x\n",
> > -                                       fault, end - 1, fault - addr,
> > -                                       fault[0], value);
> > +                               fault, end - 1, fault - addr,
> > +                               fault[0], value);
> >         print_trailer(s, page, object);
> >
> > +skip_bug_print:
> >         restore_bytes(s, what, value, fault, end);
> >         return 0;
> >  }
> > @@ -4650,9 +4684,11 @@ static int validate_slab_node(struct kmem_cache *s,
> >                 validate_slab(s, page);
> >                 count++;
> >         }
> > -       if (count != n->nr_partial)
> > +       if (count != n->nr_partial) {
> >                 pr_err("SLUB %s: %ld partial slabs counted but counter=%ld\n",
> >                        s->name, count, n->nr_partial);
> > +               slab_add_kunit_errors();
> > +       }
> >
> >         if (!(s->flags & SLAB_STORE_USER))
> >                 goto out;
> > @@ -4661,16 +4697,18 @@ static int validate_slab_node(struct kmem_cache *s,
> >                 validate_slab(s, page);
> >                 count++;
> >         }
> > -       if (count != atomic_long_read(&n->nr_slabs))
> > +       if (count != atomic_long_read(&n->nr_slabs)) {
> >                 pr_err("SLUB: %s %ld slabs counted but counter=%ld\n",
> >                        s->name, count, atomic_long_read(&n->nr_slabs));
> > +               slab_add_kunit_errors();
> > +       }
> >
> >  out:
> >         spin_unlock_irqrestore(&n->list_lock, flags);
> >         return count;
> >  }
> >
> > -static long validate_slab_cache(struct kmem_cache *s)
> > +long validate_slab_cache(struct kmem_cache *s)
> >  {
> >         int node;
> >         unsigned long count = 0;
> > @@ -4682,6 +4720,8 @@ static long validate_slab_cache(struct kmem_cache *s)
> >
> >         return count;
> >  }
> > +EXPORT_SYMBOL(validate_slab_cache);
> > +
> >  /*
> >   * Generate lists of code addresses where slabcache objects are allocated
> >   * and freed.
> > --
> > 2.31.1.272.g89b43f80a5
> >
Vlastimil Babka April 15, 2021, 10:30 a.m. UTC | #6
On 4/13/21 12:07 PM, glittao@gmail.com wrote:
> From: Oliver Glitta <glittao@gmail.com>
> 
> SLUB has resiliency_test() function which is hidden behind #ifdef
> SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody
> runs it. KUnit should be a proper replacement for it.
> 
> Try changing byte in redzone after allocation and changing
> pointer to next free node, first byte, 50th byte and redzone
> byte. Check if validation finds errors.
> 
> There are several differences from the original resiliency test:
> Tests create own caches with known state instead of corrupting
> shared kmalloc caches.
> 
> The corruption of freepointer uses correct offset, the original
> resiliency test got broken with freepointer changes.
> 
> Scratch changing random byte test, because it does not have
> meaning in this form where we need deterministic results.
> 
> Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.
> Because the test deliberatly modifies non-allocated objects, it depends on
> !KASAN which would have otherwise prevented that.
> 
> Use kunit_resource to count errors in cache and silence bug reports.
> Count error whenever slab_bug() or slab_fix() is called or when
> the count of pages is wrong.
> 
> Signed-off-by: Oliver Glitta <glittao@gmail.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

(again with a disclaimer that I'm the advisor of Oliver's student project)
Vlastimil Babka April 15, 2021, 10:38 a.m. UTC | #7
On 4/15/21 12:10 PM, Oliver Glitta wrote:
> ut 13. 4. 2021 o 15:54 Marco Elver <elver@google.com> napísal(a):
>>
>> On Tue, 13 Apr 2021 at 12:07, <glittao@gmail.com> wrote:
>> > From: Oliver Glitta <glittao@gmail.com>
>> >
>> > SLUB has resiliency_test() function which is hidden behind #ifdef
>> > SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody
>> > runs it. KUnit should be a proper replacement for it.
>> >
>> > Try changing byte in redzone after allocation and changing
>> > pointer to next free node, first byte, 50th byte and redzone
>> > byte. Check if validation finds errors.
>> >
>> > There are several differences from the original resiliency test:
>> > Tests create own caches with known state instead of corrupting
>> > shared kmalloc caches.
>> >
>> > The corruption of freepointer uses correct offset, the original
>> > resiliency test got broken with freepointer changes.
>> >
>> > Scratch changing random byte test, because it does not have
>> > meaning in this form where we need deterministic results.
>> >
>> > Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.
>> > Because the test deliberatly modifies non-allocated objects, it depends on
>> > !KASAN which would have otherwise prevented that.
>>
>> Hmm, did the test fail with KASAN? Is it possible to skip the tests
>> and still run a subset of tests with KASAN? It'd be nice if we could
>> run some of these tests with KASAN as well.
>>
>> > Use kunit_resource to count errors in cache and silence bug reports.
>> > Count error whenever slab_bug() or slab_fix() is called or when
>> > the count of pages is wrong.
>> >
>> > Signed-off-by: Oliver Glitta <glittao@gmail.com>
>>
>> Reviewed-by: Marco Elver <elver@google.com>
>>
> 
> Thank you.
> 
>> Thanks, this all looks good to me. But perhaps do test what works with
>> KASAN, to see if you need the !KASAN constraint for all cases.
> 
> I tried to run tests with KASAN functionality disabled with function
> kasan_disable_current() and three of the tests failed with wrong
> errors counts.
> So I add the !KASAN constraint for all tests, because the merge window
> is coming, we want to know if this version is stable and without other
> mistakes.
> We will take a closer look at that in the follow-up patch.

Agreed. In this context, KASAN is essentially a different implementation of the
same checks that SLUB_DEBUG offers (and also does other checks) and we excercise
these SLUB_DEBUG checks by deliberately causing the corruption that they detect
- so instead, KASAN detects it, as it should. I assume that once somebody opts
for a full KASAN kernel build, they don't need the SLUB_DEBUG functionality at
that point, as KASAN is more extensive (On the other hand SLUB_DEBUG kernels can
be (and are) shipped as production distro kernels where specific targetted
debugging can be enabled to help find bugs in production with minimal disruption).
So trying to make both cooperate can work only to some extent and for now we've
chosen the safer way.
Marco Elver April 15, 2021, 11:01 a.m. UTC | #8
On Thu, 15 Apr 2021 at 12:38, Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 4/15/21 12:10 PM, Oliver Glitta wrote:
> > ut 13. 4. 2021 o 15:54 Marco Elver <elver@google.com> napísal(a):
> >>
> >> On Tue, 13 Apr 2021 at 12:07, <glittao@gmail.com> wrote:
> >> > From: Oliver Glitta <glittao@gmail.com>
> >> >
> >> > SLUB has resiliency_test() function which is hidden behind #ifdef
> >> > SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody
> >> > runs it. KUnit should be a proper replacement for it.
> >> >
> >> > Try changing byte in redzone after allocation and changing
> >> > pointer to next free node, first byte, 50th byte and redzone
> >> > byte. Check if validation finds errors.
> >> >
> >> > There are several differences from the original resiliency test:
> >> > Tests create own caches with known state instead of corrupting
> >> > shared kmalloc caches.
> >> >
> >> > The corruption of freepointer uses correct offset, the original
> >> > resiliency test got broken with freepointer changes.
> >> >
> >> > Scratch changing random byte test, because it does not have
> >> > meaning in this form where we need deterministic results.
> >> >
> >> > Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.
> >> > Because the test deliberatly modifies non-allocated objects, it depends on
> >> > !KASAN which would have otherwise prevented that.
> >>
> >> Hmm, did the test fail with KASAN? Is it possible to skip the tests
> >> and still run a subset of tests with KASAN? It'd be nice if we could
> >> run some of these tests with KASAN as well.
> >>
> >> > Use kunit_resource to count errors in cache and silence bug reports.
> >> > Count error whenever slab_bug() or slab_fix() is called or when
> >> > the count of pages is wrong.
> >> >
> >> > Signed-off-by: Oliver Glitta <glittao@gmail.com>
> >>
> >> Reviewed-by: Marco Elver <elver@google.com>
> >>
> >
> > Thank you.
> >
> >> Thanks, this all looks good to me. But perhaps do test what works with
> >> KASAN, to see if you need the !KASAN constraint for all cases.
> >
> > I tried to run tests with KASAN functionality disabled with function
> > kasan_disable_current() and three of the tests failed with wrong
> > errors counts.
> > So I add the !KASAN constraint for all tests, because the merge window
> > is coming, we want to know if this version is stable and without other
> > mistakes.
> > We will take a closer look at that in the follow-up patch.
>
> Agreed. In this context, KASAN is essentially a different implementation of the
> same checks that SLUB_DEBUG offers (and also does other checks) and we excercise
> these SLUB_DEBUG checks by deliberately causing the corruption that they detect
> - so instead, KASAN detects it, as it should. I assume that once somebody opts
> for a full KASAN kernel build, they don't need the SLUB_DEBUG functionality at
> that point, as KASAN is more extensive (On the other hand SLUB_DEBUG kernels can
> be (and are) shipped as production distro kernels where specific targetted
> debugging can be enabled to help find bugs in production with minimal disruption).
> So trying to make both cooperate can work only to some extent and for now we've
> chosen the safer way.

Sounds reasonable. In any case, I'm fine with this version to land and
my Reviewed-by above remains valid. :-)

Thanks,
-- Marco
diff mbox series

Patch

diff --git a/include/kunit/test.h b/include/kunit/test.h
index 49601c4b98b8..524d4789af22 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -515,8 +515,9 @@  kunit_find_resource(struct kunit *test,
 		    void *match_data)
 {
 	struct kunit_resource *res, *found = NULL;
+	unsigned long flags;
 
-	spin_lock(&test->lock);
+	spin_lock_irqsave(&test->lock, flags);
 
 	list_for_each_entry_reverse(res, &test->resources, node) {
 		if (match(test, res, (void *)match_data)) {
@@ -526,7 +527,7 @@  kunit_find_resource(struct kunit *test,
 		}
 	}
 
-	spin_unlock(&test->lock);
+	spin_unlock_irqrestore(&test->lock, flags);
 
 	return found;
 }
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index ec9494e914ef..2c62eeb45b82 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -442,6 +442,7 @@  int kunit_add_resource(struct kunit *test,
 		       void *data)
 {
 	int ret = 0;
+	unsigned long flags;
 
 	res->free = free;
 	kref_init(&res->refcount);
@@ -454,10 +455,10 @@  int kunit_add_resource(struct kunit *test,
 		res->data = data;
 	}
 
-	spin_lock(&test->lock);
+	spin_lock_irqsave(&test->lock, flags);
 	list_add_tail(&res->node, &test->resources);
 	/* refcount for list is established by kref_init() */
-	spin_unlock(&test->lock);
+	spin_unlock_irqrestore(&test->lock, flags);
 
 	return ret;
 }
@@ -515,9 +516,11 @@  EXPORT_SYMBOL_GPL(kunit_alloc_and_get_resource);
 
 void kunit_remove_resource(struct kunit *test, struct kunit_resource *res)
 {
-	spin_lock(&test->lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&test->lock, flags);
 	list_del(&res->node);
-	spin_unlock(&test->lock);
+	spin_unlock_irqrestore(&test->lock, flags);
 	kunit_put_resource(res);
 }
 EXPORT_SYMBOL_GPL(kunit_remove_resource);
@@ -597,6 +600,7 @@  EXPORT_SYMBOL_GPL(kunit_kfree);
 void kunit_cleanup(struct kunit *test)
 {
 	struct kunit_resource *res;
+	unsigned long flags;
 
 	/*
 	 * test->resources is a stack - each allocation must be freed in the
@@ -608,9 +612,9 @@  void kunit_cleanup(struct kunit *test)
 	 * protect against the current node being deleted, not the next.
 	 */
 	while (true) {
-		spin_lock(&test->lock);
+		spin_lock_irqsave(&test->lock, flags);
 		if (list_empty(&test->resources)) {
-			spin_unlock(&test->lock);
+			spin_unlock_irqrestore(&test->lock, flags);
 			break;
 		}
 		res = list_last_entry(&test->resources,
@@ -621,7 +625,7 @@  void kunit_cleanup(struct kunit *test)
 		 * resource, and this can't happen if the test->lock
 		 * is held.
 		 */
-		spin_unlock(&test->lock);
+		spin_unlock_irqrestore(&test->lock, flags);
 		kunit_remove_resource(test, res);
 	}
 #if (IS_ENABLED(CONFIG_KASAN) && IS_ENABLED(CONFIG_KUNIT))