dm thin: make get_first_thin use rcu-safe list first function

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Summary

CVECVE-2025-21664
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-01-21 13:15:10 UTC
Updated2026-05-12 13:16:30 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: dm thin: make get_first_thin use rcu-safe list first function The documentation in rculist.h explains the absence of list_empty_rcu() and cautions programmers against relying on a list_empty() -> list_first() sequence in RCU safe code. This is because each of these functions performs its own READ_ONCE() of the list head. This can lead to a situation where the list_empty() sees a valid list entry, but the subsequent list_first() sees a different view of list head state after a modification. In the case of dm-thin, this author had a production box crash from a GP fault in the process_deferred_bios path. This function saw a valid list head in get_first_thin() but when it subsequently dereferenced that and turned it into a thin_c, it got the inside of the struct pool, since the list was now empty and referring to itself. The kernel on which this occurred printed both a warning about a refcount_t being saturated, and a UBSAN error for an out-of-bounds cpuid access in the queued spinlock, prior to the fault itself. When the resulting kdump was examined, it was possible to see another thread patiently waiting in thin_dtr's synchronize_rcu. The thin_dtr call managed to pull the thin_c out of the active thins list (and have it be the last entry in the active_thins list) at just the wrong moment which lead to this crash. Fortunately, the fix here is straight forward. Switch get_first_thin() function to use list_first_or_null_rcu() which performs just a single READ_ONCE() and returns NULL if the list is already empty. This was run against the devicemapper test suite's thin-provisioning suites for delete and suspend and no regressions were observed.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: NVD-CWE-noinfo

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected b10ebd34cccae1b431caf1be54919aede2be7cbe ec037fe8c0d0f6140e3d8a49c7b29cb5582160b8 git Not specified
CNA Linux Linux affected b10ebd34cccae1b431caf1be54919aede2be7cbe cd30a3960433ec2db94b3689752fa3c5df44d649 git Not specified
CNA Linux Linux affected b10ebd34cccae1b431caf1be54919aede2be7cbe 802666a40c71a23542c43a3f87e3a2d0f4e8fe45 git Not specified
CNA Linux Linux affected b10ebd34cccae1b431caf1be54919aede2be7cbe 12771050b6d059eea096993bf2001da9da9fddff git Not specified
CNA Linux Linux affected b10ebd34cccae1b431caf1be54919aede2be7cbe 6b305e98de0d225ccebfb225730a9f560d28ecb0 git Not specified
CNA Linux Linux affected b10ebd34cccae1b431caf1be54919aede2be7cbe cbd0d5ecfa390ac29c5380200147d09c381b2ac6 git Not specified
CNA Linux Linux affected b10ebd34cccae1b431caf1be54919aede2be7cbe 80f130bfad1dab93b95683fc39b87235682b8f72 git Not specified
CNA Linux Linux affected 3.15 Not specified
CNA Linux Linux unaffected 3.15 semver Not specified
CNA Linux Linux unaffected 5.4.290 5.4.* semver Not specified
CNA Linux Linux unaffected 5.10.234 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.177 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.125 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.72 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.10 6.12.* semver Not specified
CNA Linux Linux unaffected 6.13 * original_commit_for_fix Not specified
ADP Siemens SIMATIC S7-1500 TM MFP - GNU/Linux Subsystem affected * custom Not specified

References

ReferenceSourceLinkTags
lists.debian.org/debian-lts-announce/2025/03/msg00002.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/6b305e98de0d225ccebfb225730a9f560d28ecb0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/cbd0d5ecfa390ac29c5380200147d09c381b2ac6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-265688.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/80f130bfad1dab93b95683fc39b87235682b8f72 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
lists.debian.org/debian-lts-announce/2025/03/msg00001.html af854a3a-2127-422b-91ae-364da2661108 lists.debian.org
git.kernel.org/stable/c/cd30a3960433ec2db94b3689752fa3c5df44d649 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/ec037fe8c0d0f6140e3d8a49c7b29cb5582160b8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/802666a40c71a23542c43a3f87e3a2d0f4e8fe45 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/12771050b6d059eea096993bf2001da9da9fddff 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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