{"id":"CVE-2026-98866","state":"PUBLISHED","title":"sched/cache: Introduce task_struct->sched_cache_grp to fix UAF","description":"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 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().","publishedAt":"2026-10-18T15:51:27.883Z","updatedAt":"2026-10-19T09:27:00.570Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"df0d98475954d655571979aa061ecb07d7e00392","status":"affected","lessThan":"9436130e6da72af63289a4acb3aa0c1df07a3928","versionType":"git"},{"version":"df0d98475954d655571979aa061ecb07d7e00392","status":"affected","lessThan":"b636fef85bda7d1bab9c0a45067ab1508d79d946","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/exec.c","include/linux/sched.h","kernel/exit.c","kernel/fork.c","kernel/sched/fair.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.2","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.2","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/exec.c","include/linux/sched.h","kernel/exit.c","kernel/fork.c","kernel/sched/fair.c"]}],"references":["https://git.kernel.org/stable/c/9436130e6da72af63289a4acb3aa0c1df07a3928","https://git.kernel.org/stable/c/b636fef85bda7d1bab9c0a45067ab1508d79d946"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98866.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98866","state":"PUBLISHED","datePublished":"2026-10-18T15:51:27.883Z","dateUpdated":"2026-10-19T09:27:00.570Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.377Z"},"containers":{"cna":{"title":"sched/cache: Introduce task_struct->sched_cache_grp to fix UAF","descriptions":[{"lang":"en","value":"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 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()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"df0d98475954d655571979aa061ecb07d7e00392","status":"affected","lessThan":"9436130e6da72af63289a4acb3aa0c1df07a3928","versionType":"git"},{"version":"df0d98475954d655571979aa061ecb07d7e00392","status":"affected","lessThan":"b636fef85bda7d1bab9c0a45067ab1508d79d946","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/exec.c","include/linux/sched.h","kernel/exit.c","kernel/fork.c","kernel/sched/fair.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.2","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.2","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/exec.c","include/linux/sched.h","kernel/exit.c","kernel/fork.c","kernel/sched/fair.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/9436130e6da72af63289a4acb3aa0c1df07a3928"},{"url":"https://git.kernel.org/stable/c/b636fef85bda7d1bab9c0a45067ab1508d79d946"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:27:00.570Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.2","versionEndExcluding":"7.2.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.2","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}