Commit 24122c7f authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

signal: Pass pid and pid type into send_sigqueue 



Make the code more maintainable by performing more of the signal
related work in send_sigqueue.

A quick inspection of do_timer_create will show that this code path
does not lookup a thread group by a thread's pid.  Making it safe
to find the task pointed to by it_pid with "pid_task(it_pid, type)";

This supports the changes needed in fork to tell if a signal was sent
to a single process or a group of processes.

Having the pid to task transition in signal.c will also make it easier
to sort out races with de_thread and and the thread group leader
exiting when it comes time to address that.

Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 2118e1f5

include/linux/sched/signal.h

+1 −1
Original line number Diff line number Diff line
@@ -330,7 +330,7 @@ extern int send_sig(int, struct task_struct *, int); 
extern int zap_other_threads(struct task_struct *p);

extern struct sigqueue *sigqueue_alloc(void);

extern void sigqueue_free(struct sigqueue *);

extern int send_sigqueue(struct sigqueue *,  struct task_struct *, int group);

extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);

extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);



static inline int restart_syscall(void)

kernel/signal.c

+9 −5
Original line number Diff line number Diff line
@@ -1664,17 +1664,20 @@ void sigqueue_free(struct sigqueue *q) 
		__sigqueue_free(q);

}



int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)

int send_sigqueue(struct sigqueue *q, struct pid *pid, enum pid_type type)

{

	int sig = q->info.si_signo;

	struct sigpending *pending;

	struct task_struct *t;

	unsigned long flags;

	int ret, result;



	BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));



	ret = -1;

	if (!likely(lock_task_sighand(t, &flags)))

	rcu_read_lock();

	t = pid_task(pid, type);

	if (!t || !likely(lock_task_sighand(t, &flags)))

		goto ret;



	ret = 1; /* the signal is ignored */
@@ -1696,15 +1699,16 @@ int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group) 
	q->info.si_overrun = 0;



	signalfd_notify(t, sig);

	pending = group ? &t->signal->shared_pending : &t->pending;

	pending = (type != PIDTYPE_PID) ? &t->signal->shared_pending : &t->pending;

	list_add_tail(&q->list, &pending->list);

	sigaddset(&pending->signal, sig);

	complete_signal(sig, t, group);

	complete_signal(sig, t, type != PIDTYPE_PID);

	result = TRACE_SIGNAL_DELIVERED;

out:

	trace_signal_generate(sig, &q->info, t, group, result);

	trace_signal_generate(sig, &q->info, t, type != PIDTYPE_PID, result);

	unlock_task_sighand(t, &flags);

ret:

	rcu_read_unlock();

	return ret;

}

kernel/time/posix-timers.c

+4 −9
Original line number Diff line number Diff line
@@ -332,8 +332,8 @@ void posixtimer_rearm(struct siginfo *info) 


int posix_timer_event(struct k_itimer *timr, int si_private)

{

	struct task_struct *task;

	int shared, ret = -1;

	enum pid_type type;

	int ret = -1;

	/*

	 * FIXME: if ->sigq is queued we can race with

	 * dequeue_signal()->posixtimer_rearm().
@@ -347,13 +347,8 @@ int posix_timer_event(struct k_itimer *timr, int si_private) 
	 */

	timr->sigq->info.si_sys_private = si_private;



	rcu_read_lock();

	task = pid_task(timr->it_pid, PIDTYPE_PID);

	if (task) {

		shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);

		ret = send_sigqueue(timr->sigq, task, shared);

	}

	rcu_read_unlock();

	type = !(timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_TGID : PIDTYPE_PID;

	ret = send_sigqueue(timr->sigq, timr->it_pid, type);

	/* If we failed to send the signal the timer stops. */

	return ret > 0;

}

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