[PATCH 6.1.y] mptcp: fix possible integer overflow in mptcp_reset_tout_timer

["Matthieu Baerts (NGI0)" <matttbe@kernel.org>]

From: Dmitry Kandybka <d.kandybka@gmail.com>

commit b169e76ebad22cbd055101ee5aa1a7bed0e66606 upstream.

In 'mptcp_reset_tout_timer', promote 'probe_timestamp' to unsigned long
to avoid possible integer overflow. Compile tested only.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Dmitry Kandybka <d.kandybka@gmail.com>
Link: https://patch.msgid.link/20241107103657.1560536-1-d.kandybka@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Conflict in this version because commit d866ae9aaa43 ("mptcp: add a
  new sysctl for make after break timeout") is not in this version, and
  replaced TCP_TIMEWAIT_LEN in the expression. The fix can still be
  applied the same way: by forcing a cast to unsigned long for the first
  item. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/protocol.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 1acd4e37a0ea..370afcac2623 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2708,8 +2708,8 @@ void mptcp_reset_tout_timer(struct mptcp_sock *msk, unsigned long fail_tout)
 	if (!fail_tout && !inet_csk(sk)->icsk_mtup.probe_timestamp)
 		return;
 
-	close_timeout = inet_csk(sk)->icsk_mtup.probe_timestamp - tcp_jiffies32 + jiffies +
-			TCP_TIMEWAIT_LEN;
+	close_timeout = (unsigned long)inet_csk(sk)->icsk_mtup.probe_timestamp -
+			tcp_jiffies32 + jiffies + TCP_TIMEWAIT_LEN;
 
 	/* the close timeout takes precedence on the fail one, and here at least one of
 	 * them is active
-- 
2.45.2