CIFS: Do not hide EINTR after sending network packets

BugLink: https://bugs.launchpad.net/bugs/1818237

commit ee13919c upstream.

Currently we hide EINTR code returned from sock_sendmsg()
and return 0 instead. This makes a caller think that we
successfully completed the network operation which is not
true. Fix this by properly returning EINTR to callers.

Cc: <stable@vger.kernel.org>
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

fs/cifs/transport.c

@@ -364,7 +364,7 @@ __smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
 	if (rc < 0 && rc != -EINTR)
 		cifs_dbg(VFS, "Error %d sending data on socket to server\n",
 			 rc);
-	else
+	else if (rc > 0)
 		rc = 0;
 
 	return rc;