dm cache metadata: fix memory leak on metadata abort retry

Overview

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:

<snip> unreferenced object 0xffff8880080c2010 (size 16): comm "dmsetup", pid 132, jiffies 4294982580 hex dump (first 16 bytes): 00 38 b9 07 80 88 ff ff 6a 6b 6b 6b 6b 6b 6b a5 ... backtrace (crc 3118f31c): kmemleak_alloc+0x28/0x40 __kmalloc_cache_noprof+0x3d9/0x510 dm_block_manager_create+0x51/0x140 dm_cache_metadata_abort+0x85/0x320 metadata_operation_failed+0x103/0x1e0 cache_preresume+0xacd/0xe70 dm_table_resume_targets+0xd3/0x320 __dm_resume+0x1b/0xf0 dm_resume+0x127/0x170 <snip>

Affected

• Linux >= b45e77b79215405bd039a690f5b06cc03e8ed27d < 14f60e957f34f95a626caec76a8fae88cf4c397f
• Linux >= 28d307f380df88a598bc0186d527462902d9bda1 < 6b97cc7a42905755c56bbddc33aa8b792205caee
• Linux >= f74b7c5a85e22cd9091845e0d62a1dd89d0f855f < d1a79620c419a0af1911f99c873014b30740e303
• Linux >= 352b837a5541690d4f843819028cf2b8be83d424 < 15c30997dca681f90dbf2d45ee629c1828bf0c0d
• Linux >= 352b837a5541690d4f843819028cf2b8be83d424 < b0bd35535bdb6f58505f3a30ee5793986943997a
• Linux >= 352b837a5541690d4f843819028cf2b8be83d424 < 322a3b70368d49e39591fe9fc6c07d262128b05f
• Linux >= 352b837a5541690d4f843819028cf2b8be83d424 < 4311ca59a1891d33c4c8b7946f98c34f167fe833
• Linux >= 352b837a5541690d4f843819028cf2b8be83d424 < 044ca491d4086dc5bf233e9fcb71db52df32f633
• Linux 6e237cacda8b4e976849e7bff9fe7dff0e968586
• Linux 3972ae47d0ee9b5b434af5d0cca6cdfd1e239d4f
• Linux 9958f5ffc44530b650fb4cc9038a4d167fa4f5c1
• Linux f472bfc95d9c9653172dbdad39219b32fabf9b92
• Linux bdd4e106929ac943f3226d8f03754b480701e97b
• Linux >= 5.10.163 < 5.10.258
• Linux >= 5.15.87 < 5.15.209
• Linux >= 6.1.4 < 6.1.175
• Linux >= 4.9.337 < 4.10
• Linux >= 4.14.303 < 4.15
• Linux >= 4.19.270 < 4.20
• Linux >= 5.4.229 < 5.5
• Linux >= 6.0.18 < 6.1
• Linux 6.2

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.