posix-timers: Handle ignored list on delete and exit

To handle posix timer signals on sigaction(SIG_IGN) properly, the timers
will be queued on a separate ignored list.

Add the necessary cleanup code for timer_delete() and exit_itimers().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.987530588@linutronix.de

diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h
index 49a89614d90016431c056a3efb3d9dfff2f2725d..1608b52a44d5c84c99537569a6c94613921510f2 100644 (file)
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -152,7 +152,8 @@ static inline void posix_cputimers_init_work(void) { }
 
 /**
  * struct k_itimer - POSIX.1b interval timer structure.
- * @list:              List head for binding the timer to signals->posix_timers
+ * @list:              List node for binding the timer to tsk::signal::posix_timers
+ * @ignored_list:      List node for tracking ignored timers in tsk::signal::ignored_posix_timers
  * @t_hash:            Entry in the posix timer hash table
  * @it_lock:           Lock protecting the timer
  * @kclock:            Pointer to the k_clock struct handling this timer
@@ -176,6 +177,7 @@ static inline void posix_cputimers_init_work(void) { }
  */
 struct k_itimer {
        struct hlist_node       list;
+       struct hlist_node       ignored_list;
        struct hlist_node       t_hash;
        spinlock_t              it_lock;
        const struct k_clock    *kclock;

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index f20c06d0cf09d0735ea99af1c5c38fd38377f5a6..2b88fb4e937eeb1ff60dd07a3258ad2d72cb9328 100644 (file)
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -1027,6 +1027,18 @@ int common_timer_del(struct k_itimer *timer)
        return 0;
 }
 
+/*
+ * If the deleted timer is on the ignored list, remove it and
+ * drop the associated reference.
+ */
+static inline void posix_timer_cleanup_ignored(struct k_itimer *tmr)
+{
+       if (!hlist_unhashed(&tmr->ignored_list)) {
+               hlist_del_init(&tmr->ignored_list);
+               posixtimer_putref(tmr);
+       }
+}
+
 static inline int timer_delete_hook(struct k_itimer *timer)
 {
        const struct k_clock *kc = timer->kclock;
@@ -1059,6 +1071,7 @@ retry_delete:
 
        spin_lock(&current->sighand->siglock);
        hlist_del(&timer->list);
+       posix_timer_cleanup_ignored(timer);
        spin_unlock(&current->sighand->siglock);
        /*
         * A concurrent lookup could check timer::it_signal lockless. It
@@ -1110,6 +1123,8 @@ retry_delete:
        }
        hlist_del(&timer->list);
 
+       posix_timer_cleanup_ignored(timer);
+
        /*
         * Setting timer::it_signal to NULL is technically not required
         * here as nothing can access the timer anymore legitimately via
@@ -1142,6 +1157,19 @@ void exit_itimers(struct task_struct *tsk)
        /* The timers are not longer accessible via tsk::signal */
        while (!hlist_empty(&timers))
                itimer_delete(hlist_entry(timers.first, struct k_itimer, list));
+
+       /*
+        * There should be no timers on the ignored list. itimer_delete() has
+        * mopped them up.
+        */
+       if (!WARN_ON_ONCE(!hlist_empty(&tsk->signal->ignored_posix_timers)))
+               return;
+
+       hlist_move_list(&tsk->signal->ignored_posix_timers, &timers);
+       while (!hlist_empty(&timers)) {
+               posix_timer_cleanup_ignored(hlist_entry(timers.first, struct k_itimer,
+                                                       ignored_list));
+       }
 }
 
 SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,