mm: shrinker: fix shrinker_info teardown race with expansion

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-64418
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-25 10:17:25 UTC
Updated2026-07-27 05:16:48 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: mm: shrinker: fix shrinker_info teardown race with expansion expand_shrinker_info() iterates all visible memcgs under shrinker_mutex, including memcgs that have not finished ->css_online() yet. Once pn->shrinker_info has been published, teardown must stay serialized with expand_shrinker_info() until that memcg is either fully online or no longer visible to iteration. Today alloc_shrinker_info() breaks that rule by dropping shrinker_mutex before freeing a partially initialized shrinker_info array, which may cause the following race: CPU0 CPU1 ==== ==== css_create --> list_add_tail_rcu(&css->sibling, &parent_css->children); online_css --> mem_cgroup_css_online --> alloc_shrinker_info --> alloc node0 info rcu_assign_pointer(C->node0->shrinker_info, old0) alloc node1 info -> FAIL -> goto err mutex_unlock(shrinker_mutex) shrinker_alloc() --> shrinker_memcg_alloc --> mutex_lock(shrinker_mutex) expand_shrinker_info --> mem_cgroup_iter see the memcg expand_one_shrinker_info --> old0 = C->node0->shrinker_info memcpy(new->unit, old0->unit, ...); free_shrinker_info --> kvfree(old0); /* double free !! */ kvfree_rcu(old0, rcu); The same problem exists later in mem_cgroup_css_online(). If alloc_shrinker_info() succeeds but a subsequent objcg allocation fails, the free_objcg -> free_shrinker_info() unwind path tears down the already published pn->shrinker_info arrays without shrinker_mutex. The expand_one_shrinker_info() can race with that teardown in the same way, leading to use-after-free or double-free of the old shrinker_info. Fix this by serializing shrinker_info teardown with shrinker_mutex, and by keeping alloc_shrinker_info() error cleanup inside the locked section.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.001250000 probability, percentile 0.025990000 (date 2026-07-27)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 307bececcd1205bcb67a3c0d53a69db237ccc9d4 b9a280a9a454ed514636351d53fe2a233dc5054b git Not specified
CNA Linux Linux affected 307bececcd1205bcb67a3c0d53a69db237ccc9d4 6465ff3ce65131c774a312d450abe10f4b9f3875 git Not specified
CNA Linux Linux affected 307bececcd1205bcb67a3c0d53a69db237ccc9d4 284c267f013e45d8c89d9fb9373105dc8e6c0947 git Not specified
CNA Linux Linux affected 307bececcd1205bcb67a3c0d53a69db237ccc9d4 65476d31d8056e859c48580f82295ce159196ffe git Not specified
CNA Linux Linux affected 6.7 Not specified
CNA Linux Linux unaffected 6.7 semver Not specified
CNA Linux Linux unaffected 6.12.96 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.39 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.4 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/284c267f013e45d8c89d9fb9373105dc8e6c0947 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b9a280a9a454ed514636351d53fe2a233dc5054b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6465ff3ce65131c774a312d450abe10f4b9f3875 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/65476d31d8056e859c48580f82295ce159196ffe 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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