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dm cache: fix potential out-of-bounds access on the first resume

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Out-of-bounds access occurs if the fast device is expanded unexpectedly
before the first-time resume of the cache table. This happens because
expanding the fast device requires reloading the cache table for
cache_create to allocate new in-core data structures that fit the new
size, and the check in cache_preresume is not performed during the
first resume, leading to the issue.

Reproduce steps:

1. prepare component devices:

dmsetup create cmeta --table "0 8192 linear /dev/sdc 0"
dmsetup create cdata --table "0 65536 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

2. load a cache table of 512 cache blocks, and deliberately expand the
   fast device before resuming the cache, making the in-core data
   structures inadequate.

dmsetup create cache --notable
dmsetup reload cache --table "0 524288 cache /dev/mapper/cmeta \
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"
dmsetup reload cdata --table "0 131072 linear /dev/sdc 8192"
dmsetup resume cdata
dmsetup resume cache

3. suspend the cache to write out the in-core dirty bitset and hint
   array, leading to out-of-bounds access to the dirty bitset at offset
   0x40:

dmsetup suspend cache

KASAN reports:

  BUG: KASAN: vmalloc-out-of-bounds in is_dirty_callback+0x2b/0x80
  Read of size 8 at addr ffffc90000085040 by task dmsetup/90

  (...snip...)
  The buggy address belongs to the virtual mapping at
   [ffffc90000085000, ffffc90000087000) created by:
   cache_ctr+0x176a/0x35f0

  (...snip...)
  Memory state around the buggy address:
   ffffc90000084f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
   ffffc90000084f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
  >ffffc90000085000: 00 00 00 00 00 00 00 00 f8 f8 f8 f8 f8 f8 f8 f8
                                             ^
   ffffc90000085080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
   ffffc90000085100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8

Fix by checking the size change on the first resume.

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 15:13:54 +08:00 committed by Mikulas Patocka
parent f484697e61
commit c0ade5d989
1 changed files with 16 additions and 21 deletions
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37
drivers/md/dm-cache-target.c
View File

@ -2901,24 +2901,24 @@ static dm_cblock_t get_cache_dev_size(struct cache *cache)
static bool can_resize(struct cache *cache, dm_cblock_t new_size)
{
if (from_cblock(new_size) > from_cblock(cache->cache_size)) {
if (cache->sized) {
DMERR("%s: unable to extend cache due to missing cache table reload",
cache_device_name(cache));
return false;
}
DMERR("%s: unable to extend cache due to missing cache table reload",
cache_device_name(cache));
return false;
}
/*
* We can't drop a dirty block when shrinking the cache.
*/
new_size = to_cblock(find_next_bit(cache->dirty_bitset,
from_cblock(cache->cache_size),
from_cblock(new_size)));
if (new_size != cache->cache_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;
if (cache->loaded_mappings) {
new_size = to_cblock(find_next_bit(cache->dirty_bitset,
from_cblock(cache->cache_size),
from_cblock(new_size)));
if (new_size != cache->cache_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;
}
}
return true;
@ -2949,20 +2949,15 @@ static int cache_preresume(struct dm_target *ti)
/*
* Check to see if the cache has resized.
*/
if (!cache->sized) {
r = resize_cache_dev(cache, csize);
if (r)
return r;
cache->sized = true;
} else if (csize != cache->cache_size) {
if (!cache->sized || csize != cache->cache_size) {
if (!can_resize(cache, csize))
return -EINVAL;
r = resize_cache_dev(cache, csize);
if (r)
return r;
cache->sized = true;
}
if (!cache->loaded_mappings) {