{"id":"CVE-2026-98866","title":"sched/cache: Introduce task_struct->sched_cache_grp to fix UAF","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched/cache: Introduce task_struct->sched_cache_grp to fix UAF\n\nAdd a sched_cache_grp pointer to task_struct so that scheduler code\ncan access the cache group directly …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= df0d98475954d655571979aa061ecb07d7e00392 < 9436130e6da72af63289a4acb3aa0c1df07a3928","Linux >= df0d98475954d655571979aa061ecb07d7e00392 < b636fef85bda7d1bab9c0a45067ab1508d79d946","Linux 7.2"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:51:27.883Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98866","references":[{"url":"https://git.kernel.org/stable/c/9436130e6da72af63289a4acb3aa0c1df07a3928"},{"url":"https://git.kernel.org/stable/c/b636fef85bda7d1bab9c0a45067ab1508d79d946"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T16:47:32.458Z","slug":"CVE-2026-98866","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nsched/cache: Introduce task_struct->sched_cache_grp to fix UAF\n\nAdd a sched_cache_grp pointer to task_struct so that scheduler code\ncan access the cache group directly via the task, without going\nthrough mm->sched_cache_grp.  This decouples the scheduler's hot-path\naccesses from the mm_struct.\n\nEach task holds its own refcount on the sched_cache_group, separate\nfrom the reference held by its mm_struct.  The reference is acquired\nin copy_mm() (fork) and exec_mmap() (exec), and released in exit_mm().\nThis fixes the use-after-free when account_mm_sched() reaches the group\nthrough a task whose mm is being switched, as reported by Hyunwoo:\n\n  https://lore.kernel.org/lkml/apPb-Dr4nPYuHQOK@v4bel/\n\nConvert all scheduler code in fair.c and exit.c to use\np->sched_cache_grp instead of p->mm->sched_cache_grp.\n\nKeep the fork/exec/exit reference management out of the generic mm\npaths: add sched_cache_fork(), sched_cache_fork_cleanup(),\nsched_cache_exec_mmap() and sched_cache_exit_mm() in\nkernel/sched/cache_sched.c (with empty stubs for !CONFIG_SCHED_CACHE),\nso fs/exec.c, kernel/fork.c and kernel/exit.c each call one helper\ninstead of open-coding the refcounting under #ifdef.  Also add\nsched_cache_group_get() and task_cache_group_get().\n\n## Affected\n\n- `Linux >= df0d98475954d655571979aa061ecb07d7e00392 < 9436130e6da72af63289a4acb3aa0c1df07a3928`\n- `Linux >= df0d98475954d655571979aa061ecb07d7e00392 < b636fef85bda7d1bab9c0a45067ab1508d79d946`\n- `Linux 7.2`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}