From: Oleg Nesterov <oleg@redhat.com> stable inclusion from stable-v5.10.239 commit c076635b3a42771ace7d276de8dc3bc76ee2ba1b category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ICO1SY CVE: CVE-2025-38352 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit f90fff1e152dedf52b932240ebbd670d83330eca upstream. If an exiting non-autoreaping task has already passed exit_notify() and calls handle_posix_cpu_timers() from IRQ, it can be reaped by its parent or debugger right after unlock_task_sighand(). If a concurrent posix_cpu_timer_del() runs at that moment, it won't be able to detect timer->it.cpu.firing != 0: cpu_timer_task_rcu() and/or lock_task_sighand() will fail. Add the tsk->exit_state check into run_posix_cpu_timers() to fix this. This fix is not needed if CONFIG_POSIX_CPU_TIMERS_TASK_WORK=y, because exit_task_work() is called before exit_notify(). But the check still makes sense, task_work_add(&tsk->posix_cputimers_work.work) will fail anyway in this case. Cc: stable@vger.kernel.org Reported-by: Benoît Sevens <bsevens@google.com> Fixes: 0bdd2ed4138e ("sched: run_posix_cpu_timers: Don't check ->exit_state, use lock_task_sighand()") Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Conflicts: kernel/time/posix-cpu-timers.c [ conflict because 1fb497dd0030 ("posix-cpu-timers: Provide mechanisms to defer timer handling to task_work") is not merged. ] Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> --- kernel/time/posix-cpu-timers.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 5ea7ccfb62b8..3061417cc21d 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -1144,6 +1144,15 @@ void run_posix_cpu_timers(struct task_struct *tsk) lockdep_assert_irqs_disabled(); + /* + * Ensure that release_task(tsk) can't happen while + * handle_posix_cpu_timers() is running. Otherwise, a concurrent + * posix_cpu_timer_del() may fail to lock_task_sighand(tsk) and + * miss timer->it.cpu.firing != 0. + */ + if (tsk->exit_state) + return; + /* * The fast path checks that there are no expired thread or thread * group timers. If that's so, just return. -- 2.34.1