From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Moore Subject: [PATCH] unix: fix a race condition in unix_release() Date: Mon, 25 Mar 2013 09:18:33 -0400 Message-ID: <20130325131833.10376.68379.stgit@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: jan.stancek@gmail.com To: netdev@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:51283 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757889Ab3CYNSg (ORCPT ); Mon, 25 Mar 2013 09:18:36 -0400 Sender: netdev-owner@vger.kernel.org List-ID: As reported by Jan, and others over the past few years, there is a race condition caused by unix_release setting the sock->sk pointer to NULL before properly marking the socket as dead/orphaned. This can cause a problem with the LSM hook security_unix_may_send() if there is another socket attempting to write to this partially released socket in between when sock->sk is set to NULL and it is marked as dead/orphaned. This patch fixes this by only setting sock->sk to NULL after the socket has been marked as dead; I also take the opportunity to make unix_release_sock() a void function as it only ever returned 0/success. Dave, I think this one should go on the -stable pile. Special thanks to Jan for coming up with a reproducer for this problem. Reported-by: Jan Stancek Signed-off-by: Paul Moore --- net/unix/af_unix.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 51be64f..f153a8d 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -382,7 +382,7 @@ static void unix_sock_destructor(struct sock *sk) #endif } -static int unix_release_sock(struct sock *sk, int embrion) +static void unix_release_sock(struct sock *sk, int embrion) { struct unix_sock *u = unix_sk(sk); struct path path; @@ -451,8 +451,6 @@ static int unix_release_sock(struct sock *sk, int embrion) if (unix_tot_inflight) unix_gc(); /* Garbage collect fds */ - - return 0; } static void init_peercred(struct sock *sk) @@ -699,9 +697,10 @@ static int unix_release(struct socket *sock) if (!sk) return 0; + unix_release_sock(sk, 0); sock->sk = NULL; - return unix_release_sock(sk, 0); + return 0; } static int unix_autobind(struct socket *sock)