namespaces, pid_ns: fix leakage on fork() failure

Fork() failure post namespace creation for a child cloned with
CLONE_NEWPID leaks pid_namespace/mnt_cache due to proc being mounted
during creation, but not unmounted during cleanup.  Call
pid_ns_release_proc() during cleanup.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Louis Rilling <louis.rilling@kerlabs.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index b9372a0bff18..687a15d56243 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -47,6 +47,7 @@
 #include <linux/audit.h>
 #include <linux/memcontrol.h>
 #include <linux/ftrace.h>
+#include <linux/proc_fs.h>
 #include <linux/profile.h>
 #include <linux/rmap.h>
 #include <linux/ksm.h>
@@ -1464,6 +1465,8 @@ bad_fork_cleanup_io:
         if (p->io_context)
                 exit_io_context(p);
 bad_fork_cleanup_namespaces:
+        if (unlikely(clone_flags & CLONE_NEWPID))
+                pid_ns_release_proc(p->nsproxy->pid_ns);
         exit_task_namespaces(p);
 bad_fork_cleanup_mm:
         if (p->mm)