sched/cache: Introduce task_struct->sched_cache_grp to fix UAF

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Summary

CVECVE-2026-98866
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-18 16:17:41 UTC
Updated2026-10-19 10:19:50 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: sched/cache: Introduce task_struct->sched_cache_grp to fix UAF Add a sched_cache_grp pointer to task_struct so that scheduler code can access the cache group directly via the task, without going through mm->sched_cache_grp. This decouples the scheduler's hot-path accesses from the mm_struct. Each task holds its own refcount on the sched_cache_group, separate from the reference held by its mm_struct. The reference is acquired in copy_mm() (fork) and exec_mmap() (exec), and released in exit_mm(). This fixes the use-after-free when account_mm_sched() reaches the group through a task whose mm is being switched, as reported by Hyunwoo: https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/ Convert all scheduler code in fair.c and exit.c to use p->sched_cache_grp instead of p->mm->sched_cache_grp. Keep the fork/exec/exit reference management out of the generic mm paths: add sched_cache_fork(), sched_cache_fork_cleanup(), sched_cache_exec_mmap() and sched_cache_exit_mm() in kernel/sched/cache_sched.c (with empty stubs for !CONFIG_SCHED_CACHE), so fs/exec.c, kernel/fork.c and kernel/exit.c each call one helper instead of open-coding the refcounting under #ifdef. Also add sched_cache_group_get() and task_cache_group_get().

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected df0d98475954d655571979aa061ecb07d7e00392 9436130e6da72af63289a4acb3aa0c1df07a3928 git Not specified
CNA Linux Linux affected df0d98475954d655571979aa061ecb07d7e00392 b636fef85bda7d1bab9c0a45067ab1508d79d946 git Not specified
CNA Linux Linux affected 7.2 Not specified
CNA Linux Linux unaffected 7.2 semver Not specified
CNA Linux Linux unaffected 7.2.10 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/b636fef85bda7d1bab9c0a45067ab1508d79d946 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9436130e6da72af63289a4acb3aa0c1df07a3928 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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