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kasan: avoid resetting aux_lock 

With commit 63b85ac56a ("kasan: stop leaking stack trace handles"),
KASAN zeroes out alloc meta when an object is freed.  The zeroed out data
purposefully includes alloc and auxiliary stack traces but also
accidentally includes aux_lock.

As aux_lock is only initialized for each object slot during slab creation,
when the freed slot is reallocated, saving auxiliary stack traces for the
new object leads to lockdep reports when taking the zeroed out aux_lock.

Arguably, we could reinitialize aux_lock when the object is reallocated,
but a simpler solution is to avoid zeroing out aux_lock when an object
gets freed.

Link: https://lkml.kernel.org/r/20240109221234.90929-1-andrey.konovalov@linux.dev
Fixes: 63b85ac56a ("kasan: stop leaking stack trace handles")
Signed-off-by: Andrey Konovalov <andreyknvl@gmail.com>
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Closes: https://lore.kernel.org/linux-next/5cc0f83c-e1d6-45c5-be89-9b86746fe731@paulmck-laptop/
Reviewed-by: Marco Elver <elver@google.com>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andrey Konovalov 2024-01-09 23:12:34 +01:00 committed by Andrew Morton
parent aaa2c9a97c
commit cc478e0b6b
1 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
mm/kasan/generic.c
View File

@ -487,6 +487,7 @@ void kasan_init_object_meta(struct kmem_cache *cache, const void *object)
__memset(alloc_meta, 0, sizeof(*alloc_meta));
/*
* Prepare the lock for saving auxiliary stack traces.
* Temporarily disable KASAN bug reporting to allow instrumented
* raw_spin_lock_init to access aux_lock, which resides inside
* of a redzone.
@ -510,8 +511,13 @@ static void release_alloc_meta(struct kasan_alloc_meta *meta)
stack_depot_put(meta->aux_stack[0]);
stack_depot_put(meta->aux_stack[1]);
/* Zero out alloc meta to mark it as invalid. */
__memset(meta, 0, sizeof(*meta));
/*
* Zero out alloc meta to mark it as invalid but keep aux_lock
* initialized to avoid having to reinitialize it when another object
* is allocated in the same slot.
*/
__memset(&meta->alloc_track, 0, sizeof(meta->alloc_track));
__memset(meta->aux_stack, 0, sizeof(meta->aux_stack));
}
static void release_free_meta(const void *object, struct kasan_free_meta *meta)