diff mbox series

string: Add additional __realloc_size() annotations for "dup" helpers

Message ID 20240501233201.work.732-kees@kernel.org (mailing list archive)
State Superseded
Commit 450331b7338133ff77aa3908b53fed23db6d9d91
Headers show
Series string: Add additional __realloc_size() annotations for "dup" helpers | expand

Commit Message

Kees Cook May 1, 2024, 11:32 p.m. UTC 
Several other "dup"-style interfaces could use the __realloc_size()
attribute. (As a reminder to myself and others: "realloc" is used here
instead of "alloc" because the "alloc_size" attribute implies that the
memory contents are uninitialized. Since we're copying contents into the
resulting allocation, it must use "realloc_size" to avoid confusing the
compiler's optimization passes.)

Add KUnit test coverage where possible. (KUnit still does not have the
ability to manipulate userspace memory.)

Signed-off-by: Kees Cook <keescook@chromium.org>
---
Cc: Andy Shevchenko <andy@kernel.org>
Cc: linux-hardening@vger.kernel.org
---
 include/linux/string.h | 13 ++++++++-----
 lib/fortify_kunit.c    | 26 ++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 5 deletions(-)

Comments

Andy Shevchenko May 2, 2024, 9:45 a.m. UTC | #1 
On Thu, May 2, 2024 at 2:32 AM Kees Cook <keescook@chromium.org> wrote:
>
> Several other "dup"-style interfaces could use the __realloc_size()
> attribute. (As a reminder to myself and others: "realloc" is used here
> instead of "alloc" because the "alloc_size" attribute implies that the
> memory contents are uninitialized. Since we're copying contents into the
> resulting allocation, it must use "realloc_size" to avoid confusing the
> compiler's optimization passes.)
>
> Add KUnit test coverage where possible. (KUnit still does not have the
> ability to manipulate userspace memory.)

Makes sense to me,
Reviewed-by: Andy Shevchenko <andy@kernel.org>

...

> +               checker(len, kmemdup_array(test_phrases[idx], len, 1,   \
> +                                          gfp), kfree(p));             \

Despite being longer, I would put gfp on the previous line for the
sake of logical split (and additionally to be consistent with the
below).

> +               checker(len, kmemdup(test_phrases[idx], len, gfp),      \
> +                       kfree(p));                                      \
Kees Cook May 2, 2024, 2:54 p.m. UTC | #2 
On Thu, May 02, 2024 at 12:45:33PM +0300, Andy Shevchenko wrote:
> On Thu, May 2, 2024 at 2:32 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > Several other "dup"-style interfaces could use the __realloc_size()
> > attribute. (As a reminder to myself and others: "realloc" is used here
> > instead of "alloc" because the "alloc_size" attribute implies that the
> > memory contents are uninitialized. Since we're copying contents into the
> > resulting allocation, it must use "realloc_size" to avoid confusing the
> > compiler's optimization passes.)
> >
> > Add KUnit test coverage where possible. (KUnit still does not have the
> > ability to manipulate userspace memory.)
> 
> Makes sense to me,
> Reviewed-by: Andy Shevchenko <andy@kernel.org>
> 
> ...
> 
> > +               checker(len, kmemdup_array(test_phrases[idx], len, 1,   \
> > +                                          gfp), kfree(p));             \
> 
> Despite being longer, I would put gfp on the previous line for the
> sake of logical split (and additionally to be consistent with the
> below).
> 
> > +               checker(len, kmemdup(test_phrases[idx], len, gfp),      \
> > +                       kfree(p));                                      \

Oh good! This bothered me to no end too. I will adjust it. :) Thanks!

-Kees
diff mbox series

Patch

diff --git a/include/linux/string.h b/include/linux/string.h
index 86aa6cd35167..10e5177bb49c 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -14,8 +14,8 @@ 
 #include <uapi/linux/string.h>
 
 extern char *strndup_user(const char __user *, long);
-extern void *memdup_user(const void __user *, size_t);
-extern void *vmemdup_user(const void __user *, size_t);
+extern void *memdup_user(const void __user *, size_t) __realloc_size(2);
+extern void *vmemdup_user(const void __user *, size_t) __realloc_size(2);
 extern void *memdup_user_nul(const void __user *, size_t);
 
 /**
@@ -27,7 +27,8 @@  extern void *memdup_user_nul(const void __user *, size_t);
  * Return: an ERR_PTR() on failure. Result is physically
  * contiguous, to be freed by kfree().
  */
-static inline void *memdup_array_user(const void __user *src, size_t n, size_t size)
+static inline __realloc_size(2, 3)
+void *memdup_array_user(const void __user *src, size_t n, size_t size)
 {
 	size_t nbytes;
 
@@ -46,7 +47,8 @@  static inline void *memdup_array_user(const void __user *src, size_t n, size_t s
  * Return: an ERR_PTR() on failure. Result may be not
  * physically contiguous. Use kvfree() to free.
  */
-static inline void *vmemdup_array_user(const void __user *src, size_t n, size_t size)
+static inline __realloc_size(2, 3)
+void *vmemdup_array_user(const void __user *src, size_t n, size_t size)
 {
 	size_t nbytes;
 
@@ -285,7 +287,8 @@  extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
 extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
 extern void *kvmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
 extern char *kmemdup_nul(const char *s, size_t len, gfp_t gfp);
-extern void *kmemdup_array(const void *src, size_t element_size, size_t count, gfp_t gfp);
+extern void *kmemdup_array(const void *src, size_t element_size, size_t count, gfp_t gfp)
+		__realloc_size(2, 3);
 
 /* lib/argv_split.c */
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
diff --git a/lib/fortify_kunit.c b/lib/fortify_kunit.c
index 306522fd0aa2..87b873108350 100644
--- a/lib/fortify_kunit.c
+++ b/lib/fortify_kunit.c
@@ -363,6 +363,31 @@  DEFINE_ALLOC_SIZE_TEST_PAIR(kvmalloc)
 } while (0)
 DEFINE_ALLOC_SIZE_TEST_PAIR(devm_kmalloc)
 
+static const char * const test_phrases[] = {
+	"",
+	"Hello there",
+	"A longer string, just for variety",
+};
+
+#define TEST_realloc(checker)	do {					\
+	gfp_t gfp = GFP_KERNEL;						\
+	size_t len;							\
+	int idx;							\
+									\
+	for (idx = 0; idx < ARRAY_SIZE(test_phrases); idx++) {		\
+		len = strlen(test_phrases[idx]);			\
+		KUNIT_EXPECT_EQ(test, __builtin_constant_p(len), 0);	\
+		checker(len, kmemdup_array(test_phrases[idx], len, 1,	\
+					   gfp), kfree(p));		\
+		checker(len, kmemdup(test_phrases[idx], len, gfp),	\
+			kfree(p));					\
+	}								\
+} while (0)
+static void fortify_test_realloc_size(struct kunit *test)
+{
+	TEST_realloc(check_dynamic);
+}
+
 /*
  * We can't have an array at the end of a structure or else
  * builds without -fstrict-flex-arrays=3 will report them as
@@ -1046,6 +1071,7 @@  static struct kunit_case fortify_test_cases[] = {
 	KUNIT_CASE(fortify_test_alloc_size_kvmalloc_dynamic),
 	KUNIT_CASE(fortify_test_alloc_size_devm_kmalloc_const),
 	KUNIT_CASE(fortify_test_alloc_size_devm_kmalloc_dynamic),
+	KUNIT_CASE(fortify_test_realloc_size),
 	KUNIT_CASE(fortify_test_strlen),
 	KUNIT_CASE(fortify_test_strnlen),
 	KUNIT_CASE(fortify_test_strcpy),