[v2,11/11] mm: SLUB hardened usercopy support
diff mbox

Message ID 1468446964-22213-12-git-send-email-keescook@chromium.org
State New
Headers show

Commit Message

Kees Cook July 13, 2016, 9:56 p.m. UTC
Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the
SLUB allocator to catch any copies that may span objects. Includes a
redzone handling fix from Michael Ellerman.

Based on code from PaX and grsecurity.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 init/Kconfig |  1 +
 mm/slub.c    | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

Comments

Michael Ellerman July 14, 2016, 10:07 a.m. UTC | #1
Kees Cook <keescook@chromium.org> writes:

> Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the
> SLUB allocator to catch any copies that may span objects. Includes a
> redzone handling fix from Michael Ellerman.

Actually I think you wrote the fix, I just pointed you in that
direction. But anyway, this works for me, so if you like:

Tested-by: Michael Ellerman <mpe@ellerman.id.au>

cheers
Balbir Singh July 15, 2016, 2:05 a.m. UTC | #2
On Wed, Jul 13, 2016 at 02:56:04PM -0700, Kees Cook wrote:
> Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the
> SLUB allocator to catch any copies that may span objects. Includes a
> redzone handling fix from Michael Ellerman.
> 
> Based on code from PaX and grsecurity.
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  init/Kconfig |  1 +
>  mm/slub.c    | 36 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index 798c2020ee7c..1c4711819dfd 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1765,6 +1765,7 @@ config SLAB
>  
>  config SLUB
>  	bool "SLUB (Unqueued Allocator)"
> +	select HAVE_HARDENED_USERCOPY_ALLOCATOR

Should this patch come in earlier from a build perspective? I think
patch 1 introduces and uses __check_heap_object.

Balbir Singh.
Kees Cook July 15, 2016, 4:29 a.m. UTC | #3
On Thu, Jul 14, 2016 at 7:05 PM, Balbir Singh <bsingharora@gmail.com> wrote:
> On Wed, Jul 13, 2016 at 02:56:04PM -0700, Kees Cook wrote:
>> Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the
>> SLUB allocator to catch any copies that may span objects. Includes a
>> redzone handling fix from Michael Ellerman.
>>
>> Based on code from PaX and grsecurity.
>>
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> ---
>>  init/Kconfig |  1 +
>>  mm/slub.c    | 36 ++++++++++++++++++++++++++++++++++++
>>  2 files changed, 37 insertions(+)
>>
>> diff --git a/init/Kconfig b/init/Kconfig
>> index 798c2020ee7c..1c4711819dfd 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -1765,6 +1765,7 @@ config SLAB
>>
>>  config SLUB
>>       bool "SLUB (Unqueued Allocator)"
>> +     select HAVE_HARDENED_USERCOPY_ALLOCATOR
>
> Should this patch come in earlier from a build perspective? I think
> patch 1 introduces and uses __check_heap_object.

__check_heap_object in patch 1 is protected by a check for
CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR.

It seemed better to be to do arch enablement first, and then add the
per-allocator heap object size check since it was a distinct piece.
I'm happy to rearrange things, though, if there's a good reason.

-Kees

Patch
diff mbox

diff --git a/init/Kconfig b/init/Kconfig
index 798c2020ee7c..1c4711819dfd 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1765,6 +1765,7 @@  config SLAB
 
 config SLUB
 	bool "SLUB (Unqueued Allocator)"
+	select HAVE_HARDENED_USERCOPY_ALLOCATOR
 	help
 	   SLUB is a slab allocator that minimizes cache line usage
 	   instead of managing queues of cached objects (SLAB approach).
diff --git a/mm/slub.c b/mm/slub.c
index 825ff4505336..7dee3d9a5843 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3614,6 +3614,42 @@  void *__kmalloc_node(size_t size, gfp_t flags, int node)
 EXPORT_SYMBOL(__kmalloc_node);
 #endif
 
+#ifdef CONFIG_HARDENED_USERCOPY
+/*
+ * Rejects objects that are incorrectly sized.
+ *
+ * Returns NULL if check passes, otherwise const char * to name of cache
+ * to indicate an error.
+ */
+const char *__check_heap_object(const void *ptr, unsigned long n,
+				struct page *page)
+{
+	struct kmem_cache *s;
+	unsigned long offset;
+	size_t object_size;
+
+	/* Find object and usable object size. */
+	s = page->slab_cache;
+	object_size = slab_ksize(s);
+
+	/* Find offset within object. */
+	offset = (ptr - page_address(page)) % s->size;
+
+	/* Adjust for redzone and reject if within the redzone. */
+	if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) {
+		if (offset < s->red_left_pad)
+			return s->name;
+		offset -= s->red_left_pad;
+	}
+
+	/* Allow address range falling entirely within object size. */
+	if (offset <= object_size && n <= object_size - offset)
+		return NULL;
+
+	return s->name;
+}
+#endif /* CONFIG_HARDENED_USERCOPY */
+
 static size_t __ksize(const void *object)
 {
 	struct page *page;