[PATCH net-next 2/4] mptcp: options: dss: avoid printing uninit csum

When parsing the DSS suboption, this pr_debug() might read and print
uninitialised checksum value.

That's mostly harmless, but that's also confusing. Fixing that also
avoids some tools to complain about accessing uninit data.

So read this csum field only if it has been set.

Note: this was initially reported by Clashiko as an existing issue. The
code has been analysed by a human and confirmed. This is a non-urgent
fix.

Fixes: 390b95a5fb84 ("mptcp: receive checksum for DSS")
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/options.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 3b4a22846055..64aa7a516a23 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c

@@ -259,7 +259,7 @@ static void mptcp_parse_option(const struct sk_buff *skb,
 			pr_debug("data_seq=%llu subflow_seq=%u data_len=%u csum=%d:%u\n",
 				 mp_opt->data_seq, mp_opt->subflow_seq,
 				 mp_opt->data_len, !!(mp_opt->suboptions & OPTION_MPTCP_CSUMREQD),
-				 mp_opt->csum);
+				 (mp_opt->suboptions & OPTION_MPTCP_CSUMREQD) ? mp_opt->csum : 0);
 		}
 
 		break;

-- 
2.55.0