[PATCH] unshare: Use rcu_assign_pointer when setting sighand

From: ebiederm@xmission.com (Eric W. Biederman)
To: Linus Torvalds <torvalds@osdl.org>
Cc: <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@osdl.org>,
	Janak Desai <janak@us.ibm.com>, Al Viro <viro@ftp.linux.org.uk>,
	Christoph Hellwig <hch@lst.de>,
	Michael Kerrisk <mtk-manpages@gmx.net>, Andi Kleen <ak@muc.de>,
	Paul Mackerras <paulus@samba.org>,
	Oleg Nesterov <oleg@tv-sign.ru>
Subject: [PATCH] unshare: Use rcu_assign_pointer when setting sighand
Date: Thu, 16 Mar 2006 10:31:38 -0700	[thread overview]
Message-ID: <m1pskm9tz9.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <m1y7za9vy3.fsf@ebiederm.dsl.xmission.com> (Eric W. Biederman's message of "Thu, 16 Mar 2006 09:49:08 -0700")


The sighand pointer only needs the rcu_read_lock on the
read side.  So only depending on task_lock protection
when setting this pointer is not enough.  We also need
a memory barrier to ensure the initialization is seen first.

Use rcu_assign_pointer as it does this for us, and clearly
documents that we are setting an rcu readable pointer.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>


---

 kernel/fork.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

f0cdb649b7140927777f4355631648b396ee235b

diff --git a/kernel/fork.c b/kernel/fork.c
index d2706e9..2f24553 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1573,7 +1573,7 @@ asmlinkage long sys_unshare(unsigned lon
 
 		if (new_sigh) {
 			sigh = current->sighand;
-			current->sighand = new_sigh;
+			rcu_assign_pointer(current->sighand, new_sigh);
 			new_sigh = sigh;
 		}
 
-- 
1.2.4.g2d33

