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dm cache: fix out-of-bounds access to the dirty bitset when resizing

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dm-cache checks the dirty bits of the cache blocks to be dropped when
shrinking the fast device, but an index bug in bitset iteration causes
out-of-bounds access.

Reproduce steps:

1. create a cache device of 1024 cache blocks (128 bytes dirty bitset)

dmsetup create cmeta --table "0 8192 linear /dev/sdc 0"
dmsetup create cdata --table "0 131072 linear /dev/sdc 8192"
dmsetup create corig --table "0 524288 linear /dev/sdc 262144"
dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct
dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"

2. shrink the fast device to 512 cache blocks, triggering out-of-bounds
   access to the dirty bitset (offset 0x80)

dmsetup suspend cache
dmsetup reload cdata --table "0 65536 linear /dev/sdc 8192"
dmsetup resume cdata
dmsetup resume cache

KASAN reports:

  BUG: KASAN: vmalloc-out-of-bounds in cache_preresume+0x269/0x7b0
  Read of size 8 at addr ffffc900000f3080 by task dmsetup/131

  (...snip...)
  The buggy address belongs to the virtual mapping at
   [ffffc900000f3000, ffffc900000f5000) created by:
   cache_ctr+0x176a/0x35f0

  (...snip...)
  Memory state around the buggy address:
   ffffc900000f2f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
   ffffc900000f3000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  >ffffc900000f3080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                     ^
   ffffc900000f3100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
   ffffc900000f3180: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8

Fix by making the index post-incremented.

Signed-off-by: Ming-Hung Tsai <mtsai@redhat.com>
Fixes: f494a9c6b1 ("dm cache: cache shrinking support")
Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Joe Thornber <thornber@redhat.com>
This commit is contained in:
Ming-Hung Tsai 2024-10-22 15:13:16 +08:00 committed by Mikulas Patocka
parent 135496c208
commit 7922277197
1 changed files with 1 additions and 1 deletions
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2
drivers/md/dm-cache-target.c
View File

@ -2912,13 +2912,13 @@ static bool can_resize(struct cache *cache, dm_cblock_t new_size)
* We can't drop a dirty block when shrinking the cache.
*/
while (from_cblock(new_size) < from_cblock(cache->cache_size)) {
new_size = to_cblock(from_cblock(new_size) + 1);
if (is_dirty(cache, new_size)) {
DMERR("%s: unable to shrink cache; cache block %llu is dirty",
cache_device_name(cache),
(unsigned long long) from_cblock(new_size));
return false;
}
new_size = to_cblock(from_cblock(new_size) + 1);
}
return true;