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authorPaul Moore <pmoore@redhat.com>2013-03-25 03:18:33 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-04-05 10:16:53 -0700
commit92a33e58656098d3dbf538b3c1c86e6fcfbccb6c (patch)
treecd20745ee0b5864b1d4b6da618b3d291d551b8cd
parent0cbf0cbd285ef39202743ecfd62b4fe2dcdc81fd (diff)
downloadlinux-linaro-stable-92a33e58656098d3dbf538b3c1c86e6fcfbccb6c.tar.gz
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 <jan.stancek@gmail.com> Signed-off-by: Paul Moore <pmoore@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--net/unix/af_unix.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 0722a25a3a33..afbdd0c2bb71 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)