diff options
| -rw-r--r-- | queue-5.4/posix-cpu-timers-fix-race-between-handle_posix_cpu_timers-and-posix_cpu_timer_del.patch | 52 | ||||
| -rw-r--r-- | queue-5.4/series | 1 |
2 files changed, 53 insertions, 0 deletions
diff --git a/queue-5.4/posix-cpu-timers-fix-race-between-handle_posix_cpu_timers-and-posix_cpu_timer_del.patch b/queue-5.4/posix-cpu-timers-fix-race-between-handle_posix_cpu_timers-and-posix_cpu_timer_del.patch new file mode 100644 index 0000000000..6f7405708e --- /dev/null +++ b/queue-5.4/posix-cpu-timers-fix-race-between-handle_posix_cpu_timers-and-posix_cpu_timer_del.patch @@ -0,0 +1,52 @@ +From a3dbb5447bc9a8f9c04ffa5381b0a0bd77b1bdd5 Mon Sep 17 00:00:00 2001 +From: Oleg Nesterov <oleg@redhat.com> +Date: Tue, 17 Jun 2025 19:15:50 +0200 +Subject: posix-cpu-timers: fix race between handle_posix_cpu_timers() and posix_cpu_timer_del() + +From: Oleg Nesterov <oleg@redhat.com> + +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> +--- + kernel/time/posix-cpu-timers.c | 9 +++++++++ + 1 file changed, 9 insertions(+) + +--- a/kernel/time/posix-cpu-timers.c ++++ b/kernel/time/posix-cpu-timers.c +@@ -1120,6 +1120,15 @@ void run_posix_cpu_timers(void) + 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. + */ diff --git a/queue-5.4/series b/queue-5.4/series index e28c56ec3c..21efd68f2e 100644 --- a/queue-5.4/series +++ b/queue-5.4/series @@ -212,3 +212,4 @@ net-atm-fix-proc-net-atm-lec-handling.patch arm-dts-am335x-bone-common-add-gpio-phy-reset-on-revision-c3-board.patch arm-dts-am335x-bone-common-increase-mdio-reset-deassert-time.patch arm-dts-am335x-bone-common-increase-mdio-reset-deassert-delay-to-50ms.patch +posix-cpu-timers-fix-race-between-handle_posix_cpu_timers-and-posix_cpu_timer_del.patch |