[Devel] [PATCH RHEL7 COMMIT] ms/exit: pidns: alloc_pid() leaks pid_namespace if child_reaper is exiting

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-123.1.2-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-123.1.2.vz7.4.9
------>
commit 3dd868ef8c2428e0d9c9e148d9a06f972c2f7ade
Author: Oleg Nesterov <oleg at redhat.com>
Date:   Tue May 5 16:27:10 2015 +0400

    ms/exit: pidns: alloc_pid() leaks pid_namespace if child_reaper is exiting
    
    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 f02eafe..5dd2a7e 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);