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Message-ID: <20230606142033.278111872@linutronix.de>
From:   Thomas Gleixner <tglx@linutronix.de>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     Frederic Weisbecker <frederic@kernel.org>,
        Anna-Maria Behnsen <anna-maria@linutronix.de>,
        John Stultz <jstultz@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Stephen Boyd <sboyd@kernel.org>,
        Eric Biederman <ebiederm@xmission.com>,
        Oleg Nesterov <oleg@redhat.com>
Subject: [patch 40/45] posix-timers: Handle ignored list on delete and exit
References: <20230606132949.068951363@linutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Date:   Tue,  6 Jun 2023 16:38:22 +0200 (CEST)
Precedence: bulk

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>
---
 include/linux/posix-timers.h |    4 +++-
 kernel/time/posix-timers.c   |   22 ++++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -214,7 +214,8 @@ static inline void posix_cputimers_init_
 
 /**
  * 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
@@ -237,6 +238,7 @@ static inline void posix_cputimers_init_
  */
 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;
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -1032,6 +1032,18 @@ int common_timer_del(struct k_itimer *ti
 	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;
@@ -1064,6 +1076,7 @@ SYSCALL_DEFINE1(timer_delete, timer_t, t
 
 	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
@@ -1115,6 +1128,8 @@ static void itimer_delete(struct k_itime
 	}
 	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
@@ -1150,6 +1165,13 @@ void exit_itimers(struct task_struct *ts
 		tmr = hlist_entry(timers.first, struct k_itimer, list);
 		itimer_delete(tmr);
 	}
+
+	/* Mop up timers which are on the ignored list */
+	hlist_move_list(&tsk->signal->ignored_posix_timers, &timers);
+	while (!hlist_empty(&timers)) {
+		tmr = hlist_entry(timers.first, struct k_itimer, list);
+		posix_timer_cleanup_ignored(tmr);
+	}
 }
 
 SYSCALL_DEFINE2(clock_settime, const clockid_t, which_clock,