diff options
| author | Deepanshu Kartikey <kartikey406@gmail.com> | 2025-12-10 07:50:24 +0530 |
|---|---|---|
| committer | Vlastimil Babka <vbabka@suse.cz> | 2025-12-10 13:54:53 +0100 |
| commit | 53ca00a19d345197a37a1bf552e8d1e7b091666c (patch) | |
| tree | d971dec67a01f87dfee4a307634cfaf2a1ef4667 | |
| parent | 0f35040de59371ad542b915d7b91176c9910dadc (diff) | |
mm/slub: reset KASAN tag in defer_free() before accessing freed memory
When CONFIG_SLUB_TINY is enabled, kfree_nolock() calls kasan_slab_free()
before defer_free(). On ARM64 with MTE (Memory Tagging Extension),
kasan_slab_free() poisons the memory and changes the tag from the
original (e.g., 0xf3) to a poison tag (0xfe).
When defer_free() then tries to write to the freed object to build the
deferred free list via llist_add(), the pointer still has the old tag,
causing a tag mismatch and triggering a KASAN use-after-free report:
BUG: KASAN: slab-use-after-free in defer_free+0x3c/0xbc mm/slub.c:6537
Write at addr f3f000000854f020 by task kworker/u8:6/983
Pointer tag: [f3], memory tag: [fe]
Fix this by calling kasan_reset_tag() before accessing the freed memory.
This is safe because defer_free() is part of the allocator itself and is
expected to manipulate freed memory for bookkeeping purposes.
Fixes: af92793e52c3 ("slab: Introduce kmalloc_nolock() and kfree_nolock().")
Cc: stable@vger.kernel.org
Reported-by: syzbot+7a25305a76d872abcfa1@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=7a25305a76d872abcfa1
Tested-by: syzbot+7a25305a76d872abcfa1@syzkaller.appspotmail.com
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20251210022024.3255826-1-kartikey406@gmail.com
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
| -rw-r--r-- | mm/slub.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/slub.c b/mm/slub.c index f22ba8be29e0..97204d93b1dc 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -6539,6 +6539,8 @@ static void defer_free(struct kmem_cache *s, void *head) guard(preempt)(); + head = kasan_reset_tag(head); + df = this_cpu_ptr(&defer_free_objects); if (llist_add(head + s->offset, &df->objects)) irq_work_queue(&df->work); |