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Commit 3a515e4a authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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wait_task_continued/zombie: don't use task_pid_nr_ns() lockless 



Surprise, the other two wait_task_*() functions also abuse the
task_pid_nr_ns() function, and may cause read-after-free or report nr == 0
in wait_task_continued().  wait_task_zombie() doesn't have this problem,
but it is still better to cache pid_t rather than call task_pid_nr_ns()
three times on the saved pid_namespace.

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f2cc3eb1

kernel/exit.c

+5 −10
Original line number Diff line number Diff line
@@ -1189,12 +1189,9 @@ static int wait_task_zombie(struct task_struct *p, int noreap, 
{

	unsigned long state;

	int retval, status, traced;

	struct pid_namespace *ns;



	ns = current->nsproxy->pid_ns;

	pid_t pid = task_pid_nr_ns(p, current->nsproxy->pid_ns);



	if (unlikely(noreap)) {

		pid_t pid = task_pid_nr_ns(p, ns);

		uid_t uid = p->uid;

		int exit_code = p->exit_code;

		int why, status;
@@ -1313,11 +1310,11 @@ static int wait_task_zombie(struct task_struct *p, int noreap, 
			retval = put_user(status, &infop->si_status);

	}

	if (!retval && infop)

		retval = put_user(task_pid_nr_ns(p, ns), &infop->si_pid);

		retval = put_user(pid, &infop->si_pid);

	if (!retval && infop)

		retval = put_user(p->uid, &infop->si_uid);

	if (!retval)

		retval = task_pid_nr_ns(p, ns);

		retval = pid;



	if (traced) {

		write_lock_irq(&tasklist_lock);
@@ -1436,7 +1433,6 @@ static int wait_task_continued(struct task_struct *p, int noreap, 
	int retval;

	pid_t pid;

	uid_t uid;

	struct pid_namespace *ns;



	if (!(p->signal->flags & SIGNAL_STOP_CONTINUED))

		return 0;
@@ -1451,8 +1447,7 @@ static int wait_task_continued(struct task_struct *p, int noreap, 
		p->signal->flags &= ~SIGNAL_STOP_CONTINUED;

	spin_unlock_irq(&p->sighand->siglock);



	ns = current->nsproxy->pid_ns;

	pid = task_pid_nr_ns(p, ns);

	pid = task_pid_nr_ns(p, current->nsproxy->pid_ns);

	uid = p->uid;

	get_task_struct(p);

	read_unlock(&tasklist_lock);
@@ -1463,7 +1458,7 @@ static int wait_task_continued(struct task_struct *p, int noreap, 
		if (!retval && stat_addr)

			retval = put_user(0xffff, stat_addr);

		if (!retval)

			retval = task_pid_nr_ns(p, ns);

			retval = pid;

	} else {

		retval = wait_noreap_copyout(p, pid, uid,

					     CLD_CONTINUED, SIGCONT,