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: v3.4.39~19 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=fbb7347e856f5116114c3ef5945980a3afab121e;p=karo-tx-linux.git unix: fix a race condition in unix_release() [ Upstream commit ded34e0fe8fe8c2d595bfa30626654e4b87621e0 ] 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: Greg Kroah-Hartman --- diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 109e30beaa69..fa5289a5336c 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -374,7 +374,7 @@ 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; @@ -443,8 +443,6 @@ 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) @@ -694,9 +692,10 @@ 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)