In the Linux kernel, the following vulnerability has been resolved: dm cache metadata: fix...

In the Linux kernel, the following vulnerability has been resolved:

dm cache metadata: fix memory leak on metadata abort retry

When failing to acquire the root_lock in dm_cache_metadata_abort because the block_manager is read-only, the temporary block_manager created outside the root_lock is not properly released, causing a memory leak.

Reproduce steps:

This can be reproduced by reloading a new table while the metadata is read-only. While the second call to dm_cache_metadata_abort is caused by lack of support for table preload in dm-cache, mentioned in commit 9b1cc9f251af ("dm cache: share cache-metadata object across inactive and active DM tables"), it exposes the memory leak in dm_cache_metadata_abort when the function is called multiple times. Specifically, dm-cache fails to sync the new cache object's mode during preresume, creating the reproducer condition.

This issue could also occur through concurrent metadata_operation_failed calls due to races in cache mode updates, but the table preload scenario below provides a reliable reproducer.

1. Create a cache device with some faulty trailing metadata blocks

dmsetup create cmeta <<EOF 0 200 linear /dev/sdc 0 200 7992 error EOF dmsetup create cdata --table "0 131072 linear /dev/sdc 8192" dmsetup create corig --table "0 262144 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 131072 cache /dev/mapper/cmeta
/dev/mapper/cdata /dev/mapper/corig 128 1 writethrough smq 0"

2. Suspend and resume the cache to start a new metadata transaction and trigger metadata io errors on the next metadata commit.

dmsetup suspend cache dmsetup resume cache

3. Write to the cache device to update metadata

fio --filename=/dev/mapper/cache --name test --rw=randwrite --bs=4k
--randrepeat=0 --direct=1 --size 64k

4. Preload the same table

dmsetup reload cache --table "$(dmsetup table cache)"

5. Resume the new table. This triggers the memory leak.

dmsetup suspend cache dmsetup resume cache

kmemleak logs: