diff options
| author | Dmitry Vyukov <dvyukov@google.com> | 2016-10-27 17:46:44 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-27 18:43:43 -0700 |
| commit | 02754e0a484a50a92d44c38879f2cb2792ebc572 (patch) | |
| tree | 0ad938a86ba3f2b53448a41d4d2adbacf750f80a /lib | |
| parent | 0e07f663c90154079b287931257defbdb1d5405a (diff) | |
lib/stackdepot.c: bump stackdepot capacity from 16MB to 128MB
KASAN uses stackdepot to memorize stacks for all kmalloc/kfree calls.
Current stackdepot capacity is 16MB (1024 top level entries x 4 pages on
second level). Size of each stack is (num_frames + 3) * sizeof(long).
Which gives us ~84K stacks. This capacity was chosen empirically and it
is enough to run kernel normally.
However, when lots of configs are enabled and a fuzzer tries to maximize
code coverage, it easily hits the limit within tens of minutes. I've
tested for long a time with number of top level entries bumped 4x
(4096). And I think I've seen overflow only once. But I don't have all
configs enabled and code coverage has not reached maximum yet. So bump
it 8x to 8192.
Since we have two-level table, memory cost of this is very moderate --
currently the top-level table is 8KB, with this patch it is 64KB, which
is negligible under KASAN.
Here is some approx math.
128MB allows us to memorize ~670K stacks (assuming stack is ~200b).
I've grepped kernel for kmalloc|kfree|kmem_cache_alloc|kmem_cache_free|
kzalloc|kstrdup|kstrndup|kmemdup and it gives ~60K matches. Most of
alloc/free call sites are reachable with only one stack. But some
utility functions can have large fanout. Assuming average fanout is 5x,
total number of alloc/free stacks is ~300K.
Link: http://lkml.kernel.org/r/1476458416-122131-1-git-send-email-dvyukov@google.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Baozeng Ding <sploving1@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/stackdepot.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/lib/stackdepot.c b/lib/stackdepot.c index 60f77f1d470a..4d830e299989 100644 --- a/lib/stackdepot.c +++ b/lib/stackdepot.c @@ -50,7 +50,7 @@ STACK_ALLOC_ALIGN) #define STACK_ALLOC_INDEX_BITS (DEPOT_STACK_BITS - \ STACK_ALLOC_NULL_PROTECTION_BITS - STACK_ALLOC_OFFSET_BITS) -#define STACK_ALLOC_SLABS_CAP 1024 +#define STACK_ALLOC_SLABS_CAP 8192 #define STACK_ALLOC_MAX_SLABS \ (((1LL << (STACK_ALLOC_INDEX_BITS)) < STACK_ALLOC_SLABS_CAP) ? \ (1LL << (STACK_ALLOC_INDEX_BITS)) : STACK_ALLOC_SLABS_CAP) |