5.4-stable patches

added patches:
	posix-cpu-timers-fix-race-between-handle_posix_cpu_timers-and-posix_cpu_timer_del.patch

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 (file)
index 0000000..6f74057
--- /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 e28c56ec3c8dec1f289216f498cf0d7a721462f3..21efd68f2e2e6ffa841737fc1bcfd5113031f51b 100644 (file)
--- 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