pidns: fix free_pid() to handle the first fork failure

"case 0" in free_pid() assumes that disable_pid_allocation() should
clear PIDNS_HASH_ADDING before the last pid goes away.

However this doesn't happen if the first fork() fails to create the
child reaper which should call disable_pid_allocation().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/kernel/pid.c b/kernel/pid.c
index ebe5e80b10f8..9b9a26698144 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -273,6 +273,11 @@ void free_pid(struct pid *pid)
                          */
                         wake_up_process(ns->child_reaper);
                         break;
+                case PIDNS_HASH_ADDING:
+                        /* Handle a fork failure of the first process */
+                        WARN_ON(ns->child_reaper);
+                        ns->nr_hashed = 0;
+                        /* fall through */
                 case 0:
                         schedule_work(&ns->proc_work);
                         break;