[Devel] [PATCH rh7] exit: pidns: alloc_pid() leaks pid_namespace if child_reaper is exiting

[Vladimir Davydov]

From: Oleg Nesterov <oleg at redhat.com>

alloc_pid() does get_pid_ns() beforehand but forgets to put_pid_ns() if it
fails because disable_pid_allocation() was called by the exiting
child_reaper.

We could simply move get_pid_ns() down to successful return, but this fix
tries to be as trivial as possible.

Signed-off-by: Oleg Nesterov <oleg at redhat.com>
Reviewed-by: "Eric W. Biederman" <ebiederm at xmission.com>
Cc: Aaron Tomlin <atomlin at redhat.com>
Cc: Pavel Emelyanov <xemul at parallels.com>
Cc: Serge Hallyn <serge.hallyn at ubuntu.com>
Cc: Sterling Alexander <stalexan at redhat.com>
Cc: <stable at vger.kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
(cherry picked from commit 24c037ebf5723d4d9ab0996433cee4f96c292a4d)

The memory leak was found by kmemleak:

unreferenced object 0xffff880099efcec0 (size 2192):
  comm "vzctl", pid 11269, jiffies 4294743454 (age 315.703s)
  hex dump (first 32 bytes):
    27 00 00 00 00 00 00 00 ff 7f 00 00 00 00 00 00  '...............
    00 80 fa 6d 00 88 ff ff 00 80 00 00 00 00 00 00  ...m............
  backtrace:
    [<ffffffff815af0de>] kmemleak_alloc+0x4e/0xb0
    [<ffffffff8119d288>] kmem_cache_alloc+0x148/0x220
    [<ffffffff810ec283>] copy_pid_ns+0xa3/0x360
    [<ffffffff8108be93>] create_new_namespaces+0xd3/0x180
    [<ffffffff8108c045>] copy_namespaces+0x75/0x110
    [<ffffffff8105bf1f>] copy_process.part.34+0x90f/0x14e0
    [<ffffffff8105cbfc>] do_fork+0xbc/0x350
    [<ffffffff8105cf46>] SyS_clone+0x16/0x20
    [<ffffffff815da4b9>] stub_clone+0x69/0x90
    [<ffffffffffffffff>] 0xffffffffffffffff
unreferenced object 0xffff88006dfa8000 (size 4096):
  comm "vzctl", pid 11269, jiffies 4294743454 (age 315.703s)
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff815af0de>] kmemleak_alloc+0x4e/0xb0
    [<ffffffff8119d4b4>] kmem_cache_alloc_trace+0x154/0x240
    [<ffffffff810ec2a8>] copy_pid_ns+0xc8/0x360
    [<ffffffff8108be93>] create_new_namespaces+0xd3/0x180
    [<ffffffff8108c045>] copy_namespaces+0x75/0x110
    [<ffffffff8105bf1f>] copy_process.part.34+0x90f/0x14e0
    [<ffffffff8105cbfc>] do_fork+0xbc/0x350
    [<ffffffff8105cf46>] SyS_clone+0x16/0x20
    [<ffffffff815da4b9>] stub_clone+0x69/0x90
    [<ffffffffffffffff>] 0xffffffffffffffff

Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
---
 kernel/pid.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/pid.c b/kernel/pid.c
index f02eafea45ea..5dd2a7e329c1 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -336,6 +336,8 @@ out:
 
 out_unlock:
 	spin_unlock_irq(&pidmap_lock);
+	put_pid_ns(ns);
+
 out_free:
 	while (++i <= ns->level)
 		free_pidmap(pid->numbers + i);
-- 
1.7.10.4