linux-kernel - [patch V5 13/26] signal: Provide posixtimer_sigqueue

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Message-ID: <20241001083836.031093453@linutronix.de>
Date: Tue,  1 Oct 2024 10:42:17 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Anna-Maria Behnsen <anna-maria@...utronix.de>,
 Frederic Weisbecker <frederic@...nel.org>,
 John Stultz <jstultz@...gle.com>,
 Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...nel.org>,
 Stephen Boyd <sboyd@...nel.org>,
 Eric Biederman <ebiederm@...ssion.com>,
 Oleg Nesterov <oleg@...hat.com>
Subject: [patch V5 13/26] signal: Provide posixtimer_sigqueue_init()

From: Thomas Gleixner <tglx@...utronix.de>

To cure the SIG_IGN handling for posix interval timers, the preallocated
sigqueue needs to be embedded into struct k_itimer to prevent life time
races of all sorts.

Provide a new function to initialize the embedded sigqueue to prepare for
that.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 include/linux/posix-timers.h |    2 ++
 kernel/signal.c              |   11 +++++++++++
 2 files changed, 13 insertions(+)
---
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -12,6 +12,7 @@
 
 struct kernel_siginfo;
 struct task_struct;
+struct sigqueue;
 struct k_itimer;
 
 static inline clockid_t make_process_cpuclock(const unsigned int pid,
@@ -106,6 +107,7 @@ static inline void posix_cputimers_rt_wa
 }
 
 void posixtimer_rearm_itimer(struct task_struct *p);
+bool posixtimer_init_sigqueue(struct sigqueue *q);
 bool posixtimer_deliver_signal(struct kernel_siginfo *info);
 void posixtimer_free_timer(struct k_itimer *timer);
 
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1907,6 +1907,17 @@ void flush_itimer_signals(void)
 	__flush_itimer_signals(&tsk->signal->shared_pending);
 }
 
+bool posixtimer_init_sigqueue(struct sigqueue *q)
+{
+	struct ucounts *ucounts = sig_get_ucounts(current, -1, 0);
+
+	if (!ucounts)
+		return false;
+	clear_siginfo(&q->info);
+	__sigqueue_init(q, ucounts, SIGQUEUE_PREALLOC);
+	return true;
+}
+
 struct sigqueue *sigqueue_alloc(void)
 {
 	return __sigqueue_alloc(-1, current, GFP_KERNEL, 0, SIGQUEUE_PREALLOC);