Re: [PATCH net] selinux: do not report error on connect(AF_UNSPEC)

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On 5/8/19 9:32 AM, Paolo Abeni wrote:
calling connect(AF_UNSPEC) on an already connected TCP socket is an
established way to disconnect() such socket. After commit 68741a8adab9
("selinux: Fix ltp test connect-syscall failure") it no longer works
and, in the above scenario connect() fails with EAFNOSUPPORT.

Fix the above falling back to the generic/old code when the address family
is not AF_INET{4,6}, but leave the SCTP code path untouched, as it has
specific constraints.

Fixes: 68741a8adab9 ("selinux: Fix ltp test connect-syscall failure")
Reported-by: Tom Deseyn <tdeseyn@xxxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
---
  security/selinux/hooks.c | 8 ++++----
  1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index c61787b15f27..d82b87c16b0a 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -4649,7 +4649,7 @@ static int selinux_socket_connect_helper(struct socket *sock,
  		struct lsm_network_audit net = {0,};
  		struct sockaddr_in *addr4 = NULL;
  		struct sockaddr_in6 *addr6 = NULL;
-		unsigned short snum;
+		unsigned short snum = 0;
  		u32 sid, perm;
/* sctp_connectx(3) calls via selinux_sctp_bind_connect()
@@ -4674,12 +4674,12 @@ static int selinux_socket_connect_helper(struct socket *sock,
  			break;
  		default:
  			/* Note that SCTP services expect -EINVAL, whereas
-			 * others expect -EAFNOSUPPORT.
+			 * others must handle this at the protocol level:
+			 * connect(AF_UNSPEC) on a connected socket is
+			 * a documented way disconnect the socket.
  			 */
  			if (sksec->sclass == SECCLASS_SCTP_SOCKET)
  				return -EINVAL;
-			else
-				return -EAFNOSUPPORT;

I think we need to return 0 here. Otherwise, we'll fall through with an uninitialized snum, triggering a random/bogus permission check.

  		}
err = sel_netport_sid(sk->sk_protocol, snum, &sid);





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