netdev - [PATCH net-next] tcp: fix signed/unsigned comparison

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Date:   Sun, 17 Apr 2022 10:10:27 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH net-next] tcp: fix signed/unsigned comparison

From: Eric Dumazet <edumazet@...gle.com>

Kernel test robot reported:

smatch warnings:
net/ipv4/tcp_input.c:5966 tcp_rcv_established() warn: unsigned 'reason' is never less than zero.

I actually had one packetdrill failing because of this bug,
and was about to send the fix :)

Fixes: 4b506af9c5b8 ("tcp: add two drop reasons for tcp_ack()")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: kernel test robot <lkp@...el.com>
---
 net/ipv4/tcp_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cf2dc19bb8c766c1d33406053fd61c0873f15489..0d88984e071531fb727bdee178b0c01fd087fe5f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5959,7 +5959,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 
 step5:
 	reason = tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT);
-	if (reason < 0)
+	if ((int)reason < 0)
 		goto discard;
 
 	tcp_rcv_rtt_measure_ts(sk, skb);
-- 
2.36.0.rc0.470.gd361397f0d-goog