Commit 5cac427f authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

signal: Split up __sigqueue_alloc() 



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.

Reorganize __sigqueue_alloc() so the ucounts retrieval and the
initialization can be used independently.

No functional change.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/all/20241105064213.371410037@linutronix.de
parent 5d916a09

kernel/signal.c

+35 −17
Original line number Diff line number Diff line
@@ -396,16 +396,9 @@ void task_join_group_stop(struct task_struct *task) 
	task_set_jobctl_pending(task, mask | JOBCTL_STOP_PENDING);

}



/*

 * allocate a new signal queue record

 * - this may be called without locks if and only if t == current, otherwise an

 *   appropriate lock must be held to stop the target task from exiting

 */

static struct sigqueue *

__sigqueue_alloc(int sig, struct task_struct *t, gfp_t gfp_flags,

		 int override_rlimit, const unsigned int sigqueue_flags)

static struct ucounts *sig_get_ucounts(struct task_struct *t, int sig,

				       int override_rlimit)

{

	struct sigqueue *q = NULL;

	struct ucounts *ucounts;

	long sigpending;
@@ -424,19 +417,44 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t gfp_flags, 
	if (!sigpending)

		return NULL;



	if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) {

		q = kmem_cache_alloc(sigqueue_cachep, gfp_flags);

	} else {

	if (unlikely(!override_rlimit && sigpending > task_rlimit(t, RLIMIT_SIGPENDING))) {

		dec_rlimit_put_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING);

		print_dropped_signal(sig);

		return NULL;

	}



	if (unlikely(q == NULL)) {

		dec_rlimit_put_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING);

	} else {

	return ucounts;

}



static void __sigqueue_init(struct sigqueue *q, struct ucounts *ucounts,

			    const unsigned int sigqueue_flags)

{

	INIT_LIST_HEAD(&q->list);

	q->flags = sigqueue_flags;

	q->ucounts = ucounts;

}



/*

 * allocate a new signal queue record

 * - this may be called without locks if and only if t == current, otherwise an

 *   appropriate lock must be held to stop the target task from exiting

 */

static struct sigqueue *__sigqueue_alloc(int sig, struct task_struct *t, gfp_t gfp_flags,

					 int override_rlimit, const unsigned int sigqueue_flags)

{

	struct ucounts *ucounts = sig_get_ucounts(t, sig, override_rlimit);

	struct sigqueue *q;



	if (!ucounts)

		return NULL;



	q = kmem_cache_alloc(sigqueue_cachep, gfp_flags);

	if (!q) {

		dec_rlimit_put_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING);

		return NULL;

	}



	__sigqueue_init(q, ucounts, sigqueue_flags);

	return q;

}