linux-kernel - [PATCH] pidns: Fix a leak in /proc inodes and dentries

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Date:	Mon, 19 Oct 2009 21:13:37 -0700
From:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	dlezcano@...ibm.com, ebiederm@...ssion.com, jack@....cz,
	andrea@...share.com, sukadev@...ibm.com,
	Containers <containers@...ts.linux-foundation.org>,
	linux-kernel@...r.kernel.org, Pavel Emelyanov <xemul@...nvz.org>,
	mingo@...e.hu, Alexey Dobriyan <adobriyan@...il.com>
Subject: [PATCH] pidns: Fix a leak in /proc inodes and dentries

Fix a leak in /proc dentries and inodes with pid namespaces.

This fix reverts the commit 7766755a2f249e7e0. The leak was reported by
Daniel Lezcano - see  http://lkml.org/lkml/2009/10/2/159.

To summarize the thread, when container-init is terminated, it sets the
PF_EXITING flag and then zaps all the other processes in the container.
When those processes exit, they are expected to be reaped by the container-
init and as a part of reaping, the container-init should flush any /proc
dentries associated with the processes. But because the container-init is
itself exiting and the following PF_EXITING check, the dentires are not
flushed, resulting in leak in /proc inodes and dentries.

Signed-off-by: Sukadev Bhattiprolu <sukadev@...ibm.com>
Reported-by: Daniel Lezcano <dlezcano@...ibm.com>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Cc: Jan Kara <jack@....cz>
Cc: Andrea Arcangeli <andrea@...share.com>

---
 fs/proc/base.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Index: linux-2.6/fs/proc/base.c
===================================================================
--- linux-2.6.orig/fs/proc/base.c	2009-10-19 20:28:51.000000000 -0700
+++ linux-2.6/fs/proc/base.c	2009-10-19 20:29:03.000000000 -0700
@@ -2580,8 +2580,7 @@ static void proc_flush_task_mnt(struct v
 	name.len = snprintf(buf, sizeof(buf), "%d", pid);
 	dentry = d_hash_and_lookup(mnt->mnt_root, &name);
 	if (dentry) {
-		if (!(current->flags & PF_EXITING))
-			shrink_dcache_parent(dentry);
+		shrink_dcache_parent(dentry);
 		d_drop(dentry);
 		dput(dentry);
 	}
--
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