netdev - [PATCH net] sctp: make sctp_setsockopt_events() less strict about the option length

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Message-Id: <20190206201430.18830-1-julien@arista.com>
Date:   Wed,  6 Feb 2019 12:14:30 -0800
From:   Julien Gomes <julien@...sta.com>
To:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     davem@...emloft.net, marcelo.leitner@...il.com,
        nhorman@...driver.com, vyasevich@...il.com, lucien.xin@...il.com,
        Julien Gomes <julien@...sta.com>
Subject: [PATCH net] sctp: make sctp_setsockopt_events() less strict about the option length

Make sctp_setsockopt_events() able to accept sctp_event_subscribe
structures longer than the current definitions.

This should prevent unjustified setsockopt() failures due to struct
sctp_event_subscribe extensions (as in 4.11 and 4.12) when using
binaries that should be compatible, but were built with later kernel
uapi headers.

Signed-off-by: Julien Gomes <julien@...sta.com>
---
 net/sctp/socket.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 9644bdc8e85c..f9717e2789da 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -2311,7 +2311,7 @@ static int sctp_setsockopt_events(struct sock *sk, char __user *optval,
 	int i;
 
 	if (optlen > sizeof(struct sctp_event_subscribe))
-		return -EINVAL;
+		optlen = sizeof(struct sctp_event_subscribe);
 
 	if (copy_from_user(&subscribe, optval, optlen))
 		return -EFAULT;
-- 
2.20.1