From ded34e0fe8fe8c2d595bfa30626654e4b87621e0 Mon Sep 17 00:00:00 2001 From: Paul Moore Date: Mon, 25 Mar 2013 03:18:33 +0000 Subject: unix: fix a race condition in unix_release() 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 --- net/unix/af_unix.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'net/unix/af_unix.c') diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index 51be64f163ec..f153a8d6e339 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) -- cgit From 14134f6584212d585b310ce95428014b653dfaf6 Mon Sep 17 00:00:00 2001 From: dingtianhong Date: Mon, 25 Mar 2013 17:02:04 +0000 Subject: af_unix: dont send SCM_CREDENTIAL when dest socket is NULL SCM_SCREDENTIALS should apply to write() syscalls only either source or destination socket asserted SOCK_PASSCRED. The original implememtation in maybe_add_creds is wrong, and breaks several LSB testcases ( i.e. /tset/LSB.os/netowkr/recvfrom/T.recvfrom). Origionally-authored-by: Karel Srot Signed-off-by: Ding Tianhong Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/unix/af_unix.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'net/unix/af_unix.c') diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index f153a8d6e339..971282b6f6a3 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1412,8 +1412,8 @@ static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock, if (UNIXCB(skb).cred) return; if (test_bit(SOCK_PASSCRED, &sock->flags) || - !other->sk_socket || - test_bit(SOCK_PASSCRED, &other->sk_socket->flags)) { + (other->sk_socket && + test_bit(SOCK_PASSCRED, &other->sk_socket->flags))) { UNIXCB(skb).pid = get_pid(task_tgid(current)); UNIXCB(skb).cred = get_current_cred(); } -- cgit