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Commit b0ba0d34 authored by Andrey Ryabinin's avatar Andrey Ryabinin Committed by Trilok Soni
Browse files

mm, slub, kasan: enable user tracking by default with KASAN=y 



It's recommended to have slub's user tracking enabled with CONFIG_KASAN,
because:

a) User tracking disables slab merging which improves
    detecting out-of-bounds accesses.
b) User tracking metadata acts as redzone which also improves
    detecting out-of-bounds accesses.
c) User tracking provides additional information about object.
    This information helps to understand bugs.

Currently it is not enabled by default.  Besides recompiling the kernel
with KASAN and reinstalling it, user also have to change the boot cmdline,
which is not very handy.

Enable slub user tracking by default with KASAN=y, since there is no good
reason to not do this.

[akpm@linux-foundation.org: little fixes, per David]
Signed-off-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Git-commit: 89d3c87e20d95e3238eac85e43de7b3cb1f39d8b
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: default avatarTrilok Soni <tsoni@codeaurora.org>
parent 24bd3f90

Documentation/kasan.txt

+1 −2
Original line number Diff line number Diff line
@@ -28,8 +28,7 @@ the latter is 1.1 - 2 times faster. Inline instrumentation requires a GCC 
version 5.0 or later.



Currently KASAN works only with the SLUB memory allocator.

For better bug detection and nicer report, enable CONFIG_STACKTRACE and put

at least 'slub_debug=U' in the boot cmdline.

For better bug detection and nicer reporting, enable CONFIG_STACKTRACE.



To disable instrumentation for specific files or directories, add a line

similar to the following to the respective kernel Makefile:

lib/Kconfig.kasan

+1 −2
Original line number Diff line number Diff line
@@ -15,8 +15,7 @@ config KASAN 
	  global variables requires gcc 5.0 or later.

	  This feature consumes about 1/8 of available memory and brings about

	  ~x3 performance slowdown.

	  For better error detection enable CONFIG_STACKTRACE,

	  and add slub_debug=U to boot cmdline.

	  For better error detection enable CONFIG_STACKTRACE.

	  See KASAN_SANITIZE_ALL for selectively compiling files and directories

	  with this compiler feature enabled.

mm/slub.c

+3 −1
Original line number Diff line number Diff line
@@ -459,8 +459,10 @@ static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map) 
/*

 * Debug settings:

 */

#ifdef CONFIG_SLUB_DEBUG_ON

#if defined(CONFIG_SLUB_DEBUG_ON)

static int slub_debug = DEBUG_DEFAULT_FLAGS;

#elif defined(CONFIG_KASAN)

static int slub_debug = SLAB_STORE_USER;

#else

static int slub_debug;

#endif