[PATCH] libceph: reject bad connect_seq in msgr1 READY reply

[Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>]

process_connect() WARN_ON()s when the peer's READY/SEQ reply carries a
connect_seq other than ours + 1. That value comes off the wire, so a
misbehaving or malicious server can trigger the warning at will (and
panic machines running with panic_on_warn).

Check it before touching connection state and fail the connection with
a protocol error instead, like the other bad-reply cases here.

Reported-by: syzbot+21f8628595b2061c438d@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=21f8628595b2061c438d
Fixes: 31b8006e10a4 ("ceph: messenger library")
Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@gmail.com>
---
 net/ceph/messenger_v1.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ceph/messenger_v1.c b/net/ceph/messenger_v1.c
index c9e002d96319..b3ff3274344e 100644
--- a/net/ceph/messenger_v1.c
+++ b/net/ceph/messenger_v1.c
@@ -887,6 +887,12 @@ static int process_connect(struct ceph_connection *con)
 			return -1;
 		}
 
+		if (le32_to_cpu(con->v1.in_reply.connect_seq) !=
+		    con->v1.connect_seq + 1) {
+			con->error_msg = "protocol error, bad connect_seq";
+			return -1;
+		}
+
 		WARN_ON(con->state != CEPH_CON_S_V1_CONNECT_MSG);
 		con->state = CEPH_CON_S_OPEN;
 		con->v1.auth_retry = 0;    /* we authenticated; clear flag */
@@ -898,8 +904,6 @@ static int process_connect(struct ceph_connection *con)
 		     con->v1.peer_global_seq,
 		     le32_to_cpu(con->v1.in_reply.connect_seq),
 		     con->v1.connect_seq);
-		WARN_ON(con->v1.connect_seq !=
-			le32_to_cpu(con->v1.in_reply.connect_seq));
 
 		if (con->v1.in_reply.flags & CEPH_MSG_CONNECT_LOSSY)
 			ceph_con_flag_set(con, CEPH_CON_F_LOSSYTX);
-- 
2.43.0