Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Sun, 07 Apr 2013 23:45:43 +0100 | Subject | [59/74] unix: fix a race condition in unix_release() |
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3.2.43-rc1 review patch. If anyone has any objections, please let me know.
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From: Paul Moore <pmoore@redhat.com>
[ 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 <jan.stancek@gmail.com> Signed-off-by: Paul Moore <pmoore@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- 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 317bfe3..18978b6 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -371,7 +371,7 @@ 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; @@ -444,8 +444,6 @@ 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) @@ -682,9 +680,10 @@ 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)
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