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Commit c8950783 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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wait_task_stopped(): don't use task_pid_nr_ns() lockless 



wait_task_stopped(WNOWAIT) does task_pid_nr_ns() without tasklist/rcu lock,
we can read an already freed memory.  Use the cached pid_t value.

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Looks-good-to: Roland McGrath <roland@redhat.com>
Acked-by: default avatarPavel Emelyanov <xemul@openvz.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c2319540

kernel/exit.c

+4 −5
Original line number Diff line number Diff line
@@ -1357,7 +1357,7 @@ static int wait_task_stopped(struct task_struct *p, int delayed_group_leader, 
			     int __user *stat_addr, struct rusage __user *ru)

{

	int retval, exit_code;

	struct pid_namespace *ns;

	pid_t pid;



	if (!p->exit_code)

		return 0;
@@ -1376,12 +1376,11 @@ static int wait_task_stopped(struct task_struct *p, int delayed_group_leader, 
	 * keep holding onto the tasklist_lock while we call getrusage and

	 * possibly take page faults for user memory.

	 */

	ns = current->nsproxy->pid_ns;

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

	get_task_struct(p);

	read_unlock(&tasklist_lock);



	if (unlikely(noreap)) {

		pid_t pid = task_pid_nr_ns(p, ns);

		uid_t uid = p->uid;

		int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
@@ -1451,11 +1450,11 @@ bail_ref: 
	if (!retval && infop)

		retval = put_user(exit_code, &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;

	put_task_struct(p);



	BUG_ON(!retval);