+ kasan-fix-null-pointer-dereference-in-kasan_record_aux_stack.patch added to -mm tree

+ kasan-fix-null-pointer-dereference-in-kasan_record_aux_stack.patch added to -mm tree

[akpm]

The patch titled
     Subject: kasan: fix null pointer dereference in kasan_record_aux_stack
has been added to the -mm tree.  Its filename is
     kasan-fix-null-pointer-dereference-in-kasan_record_aux_stack.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/kasan-fix-null-pointer-dereference-in-kasan_record_aux_stack.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/kasan-fix-null-pointer-dereference-in-kasan_record_aux_stack.patch

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------------------------------------------------------
From: Walter Wu <walter-zh.wu@mediatek.com>
Subject: kasan: fix null pointer dereference in kasan_record_aux_stack

Syzbot reported the following [1]:

 BUG: kernel NULL pointer dereference, address: 0000000000000008
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 2d993067 P4D 2d993067 PUD 19a3c067 PMD 0
 Oops: 0000 [#1] PREEMPT SMP KASAN
 CPU: 1 PID: 3852 Comm: kworker/1:2 Not tainted 5.10.0-syzkaller #0
 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 Workqueue: events free_ipc
 RIP: 0010:kasan_record_aux_stack+0x77/0xb0

Add null checking slab object from kasan_get_alloc_meta()
in order to avoid null pointer dereference.

[1] https://syzkaller.appspot.com/x/log.txt?x=10a82a50d00000

Link: https://lkml.kernel.org/r/20201228080018.23041-1-walter-zh.wu@mediatek.com
Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/kasan/generic.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/kasan/generic.c~kasan-fix-null-pointer-dereference-in-kasan_record_aux_stack
+++ a/mm/kasan/generic.c
@@ -337,6 +337,8 @@ void kasan_record_aux_stack(void *addr)
 	cache = page->slab_cache;
 	object = nearest_obj(cache, page, addr);
 	alloc_meta = kasan_get_alloc_meta(cache, object);
+	if (!alloc_meta)
+		return;
 
 	alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0];
 	alloc_meta->aux_stack[0] = kasan_save_stack(GFP_NOWAIT);
_

Patches currently in -mm which might be from walter-zh.wu@mediatek.com are

kasan-fix-null-pointer-dereference-in-kasan_record_aux_stack.patch