From: Eric Dumazet <edumazet@google.com>
Date: Sun, 17 Apr 2022 18:34:32 +0000 (-0700)
Subject: tcp: fix signed/unsigned comparison
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=843f77407eebee07c2a3300df0c4b33f64322e29;p=linux.git

tcp: fix signed/unsigned comparison

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 :)

v2: Andreas Schwab also pointed out that @reason needs to be negated
    before we reach tcp_drop_reason()

Fixes: 4b506af9c5b8 ("tcp: add two drop reasons for tcp_ack()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cf2dc19bb8c76..daff631b94865 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5959,9 +5959,10 @@ slow_path:
 
 step5:
 	reason = tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT);
-	if (reason < 0)
+	if ((int)reason < 0) {
+		reason = -reason;
 		goto discard;
-
+	}
 	tcp_rcv_rtt_measure_ts(sk, skb);
 
 	/* Process urgent data. */