From: Paul Moore Date: Mon, 25 Mar 2013 03:18:33 +0000 (+0000) Subject: unix: fix a race condition in unix_release() X-Git-Tag: v2.6.34.15~176 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=b34a6044b346f2277fe6e2318db1da2abfd1bf65;p=thirdparty%2Fkernel%2Fstable.git unix: fix a race condition in unix_release() commit ded34e0fe8fe8c2d595bfa30626654e4b87621e0 upstream. 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 Signed-off-by: David S. Miller Signed-off-by: Paul Gortmaker --- diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 0b7148bed6b31..072835bc61fa7 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -370,7 +370,7 @@ 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 dentry *dentry; @@ -445,8 +445,6 @@ static int unix_release_sock(struct sock *sk, int embrion) if (unix_tot_inflight) unix_gc(); /* Garbage collect fds */ - - return 0; } static int unix_listen(struct socket *sock, int backlog) @@ -661,9 +659,10 @@ 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)