Subject: [PATCH 09/12] mptcp: bugfix for RM_ADDR option parsing

From: Geliang Tang <[email-masked]>
Date: Mon, 8 Jun 2020 18:47:54 +0800

[ Upstream commit 8e60eed6b38e464e8c9d68f9caecafaa554dffe0 ]

In MPTCPOPT_RM_ADDR option parsing, the pointer "ptr" pointed to the
"Subtype" octet, the pointer "ptr+1" pointed to the "Address ID" octet:

  +-------+-------+---------------+
  |Subtype|(resvd)|   Address ID  |
  +-------+-------+---------------+
  |               |
 ptr            ptr+1

We should set mp_opt->rm_id to the value of "ptr+1", not "ptr". This patch
will fix this bug.

Fixes: 3df523ab582c ("mptcp: Add ADD_ADDR handling")
Signed-off-by: Geliang Tang <[email-masked]>
Reviewed-by: Matthieu Baerts <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/mptcp/options.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 7793b6011fa7..1c20dd14b2aa 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -273,6 +273,8 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 		if (opsize != TCPOLEN_MPTCP_RM_ADDR_BASE)
 			break;
 
+		ptr++;
+
 		mp_opt->rm_addr = 1;
 		mp_opt->rm_id = *ptr++;
 		pr_debug("RM_ADDR: id=%d", mp_opt->rm_id);
-- 
2.26.2