[PATCH net 1/5] mptcp: mptcp_parse_option() fix for MPTCPOPT_MP_JOIN

[Eric Dumazet <edumazet@google.com>]

mptcp_parse_option() currently sets OPTIONS_MPTCP_MPJ, for the three
possible cases handled for MPTCPOPT_MP_JOIN option.

OPTIONS_MPTCP_MPJ is the combination of three flags:
- OPTION_MPTCP_MPJ_SYN
- OPTION_MPTCP_MPJ_SYNACK
- OPTION_MPTCP_MPJ_ACK

This is a problem, because backup, join_id, token, nonce and/or hmac fields
could be left uninitialized in some cases.

Distinguish the three cases, as following patches will need this step.

Fixes: f296234c98a8 ("mptcp: Add handling of incoming MP_JOIN requests")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Cc: Peter Krystad <peter.krystad@linux.intel.com>
Cc: Matthieu Baerts <matttbe@kernel.org>
Cc: Mat Martineau <martineau@kernel.org>
Cc: Geliang Tang <geliang.tang@linux.dev>
---
 net/mptcp/options.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index c53914012d01d38c2dc0a3578bf3651595956e72..d2527d189a799319c068a5b76a5816cc7a905861 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -123,8 +123,8 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		break;
 
 	case MPTCPOPT_MP_JOIN:
-		mp_opt->suboptions |= OPTIONS_MPTCP_MPJ;
 		if (opsize == TCPOLEN_MPTCP_MPJ_SYN) {
+			mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYN;
 			mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 			mp_opt->join_id = *ptr++;
 			mp_opt->token = get_unaligned_be32(ptr);
@@ -135,6 +135,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 				 mp_opt->backup, mp_opt->join_id,
 				 mp_opt->token, mp_opt->nonce);
 		} else if (opsize == TCPOLEN_MPTCP_MPJ_SYNACK) {
+			mp_opt->suboptions |= OPTION_MPTCP_MPJ_SYNACK;
 			mp_opt->backup = *ptr++ & MPTCPOPT_BACKUP;
 			mp_opt->join_id = *ptr++;
 			mp_opt->thmac = get_unaligned_be64(ptr);
@@ -145,11 +146,10 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 				 mp_opt->backup, mp_opt->join_id,
 				 mp_opt->thmac, mp_opt->nonce);
 		} else if (opsize == TCPOLEN_MPTCP_MPJ_ACK) {
+			mp_opt->suboptions |= OPTION_MPTCP_MPJ_ACK;
 			ptr += 2;
 			memcpy(mp_opt->hmac, ptr, MPTCPOPT_HMAC_LEN);
 			pr_debug("MP_JOIN hmac");
-		} else {
-			mp_opt->suboptions &= ~OPTIONS_MPTCP_MPJ;
 		}
 		break;
 
-- 
2.43.0.275.g3460e3d667-goog