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: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/exit.c b/kernel/exit.c
index ee60772..dee8b4d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1189,12 +1189,9 @@
{
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 @@
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 @@
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 @@
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 @@
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,