smack: unix sockets: fix accept()ed socket label

When a process accept()s connection from a unix socket
(either stream or seqpacket)
it gets the socket with the label of the connecting process.

For example, if a connecting process has a label 'foo',
the accept()ed socket will also have 'in' and 'out' labels 'foo',
regardless of the label of the listener process.

This is because kernel creates unix child sockets
in the context of the connecting process.

I do not see any obvious way for the listener to abuse
alien labels coming with the new socket, but,
to be on the safe side, it's better fix new socket labels.

Signed-off-by: Konstantin Andreev <andreev@swemel.ru>
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 56e02cc5c44d..d0d484c1599a 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3846,12 +3846,18 @@ static int smack_unix_stream_connect(struct sock *sock,
 		}
 	}
 
-	/*
-	 * Cross reference the peer labels for SO_PEERSEC.
-	 */
 	if (rc == 0) {
+		/*
+		 * Cross reference the peer labels for SO_PEERSEC.
+		 */
 		nsp->smk_packet = ssp->smk_out;
 		ssp->smk_packet = osp->smk_out;
+
+		/*
+		 * new/child/established socket must inherit listening socket labels
+		 */
+		nsp->smk_out = osp->smk_out;
+		nsp->smk_in  = osp->smk_in;
 	}
 
 	return rc;