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

dm cache: fix null-deref with concurrent writes in passthrough mode

In passthrough mode, when dm-cache starts to invalidate a cache
entry and bio prison cell lock fails due to concurrent write to
the same cached block, mg->cell remains NULL. The error path in
invalidate_complete() attempts to unlock and free the cell
unconditionally, causing a NULL pointer dereference:

KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 0 UID: 0 PID: 134 Comm: fio Not tainted 6.19.0-rc7 #3 PREEMPT
RIP: 0010:dm_cell_unlock_v2+0x3f/0x210
<snip>
Call Trace:
invalidate_complete+0xef/0x430
map_bio+0x130f/0x1a10
cache_map+0x320/0x6b0
__map_bio+0x458/0x510
dm_submit_bio+0x40e/0x16d0
__submit_bio+0x419/0x870
<snip>

Reproduce steps:

1. Create a cache device

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

2. Promote the first data block into cache

fio --filename=/dev/mapper/cache --name=populate --rw=write --bs=4k \
--direct=1 --size=64k

3. Reload the cache into passthrough mode

dmsetup suspend cache
dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0"
dmsetup resume cache

4. Write to the first cached block concurrently

fio --filename=/dev/mapper/cache --name test --rw=randwrite --bs=4k \
--randrepeat=0 --direct=1 --numjobs=2 --size 64k

Fix by checking if mg->cell is valid before attempting to unlock it.

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Debian DLA Debian DLA DLA-4664-1 linux security update
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Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Sat, 27 Jun 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-367
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Low


Wed, 24 Jun 2026 21:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-476

Wed, 24 Jun 2026 17:15:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: dm cache: fix null-deref with concurrent writes in passthrough mode In passthrough mode, when dm-cache starts to invalidate a cache entry and bio prison cell lock fails due to concurrent write to the same cached block, mg->cell remains NULL. The error path in invalidate_complete() attempts to unlock and free the cell unconditionally, causing a NULL pointer dereference: KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] CPU: 0 UID: 0 PID: 134 Comm: fio Not tainted 6.19.0-rc7 #3 PREEMPT RIP: 0010:dm_cell_unlock_v2+0x3f/0x210 <snip> Call Trace: invalidate_complete+0xef/0x430 map_bio+0x130f/0x1a10 cache_map+0x320/0x6b0 __map_bio+0x458/0x510 dm_submit_bio+0x40e/0x16d0 __submit_bio+0x419/0x870 <snip> Reproduce steps: 1. Create a cache device 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 262144 linear /dev/sdc 262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 oflag=direct dmsetup create cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 2. Promote the first data block into cache fio --filename=/dev/mapper/cache --name=populate --rw=write --bs=4k \ --direct=1 --size=64k 3. Reload the cache into passthrough mode dmsetup suspend cache dmsetup reload cache --table "0 262144 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 passthrough smq 0" dmsetup resume cache 4. Write to the first cached block concurrently fio --filename=/dev/mapper/cache --name test --rw=randwrite --bs=4k \ --randrepeat=0 --direct=1 --numjobs=2 --size 64k Fix by checking if mg->cell is valid before attempting to unlock it.
Title dm cache: fix null-deref with concurrent writes in passthrough mode
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-06-24T16:30:07.536Z

Reserved: 2026-06-09T07:44:35.382Z

Link: CVE-2026-53064

cve-icon Vulnrichment

No data.

cve-icon NVD

No data.

cve-icon Redhat

Severity : Low

Publid Date: 2026-06-24T00:00:00Z

Links: CVE-2026-53064 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-06-27T02:00:10Z

Weaknesses