[PATCH v2 net-next] tcp: fix signed/unsigned comparison

[PATCH v2 net-next] tcp: fix signed/unsigned comparison

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.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 :)

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>
---
 net/ipv4/tcp_input.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cf2dc19bb8c766c1d33406053fd61c0873f15489..daff631b94865ae95cbd49ed8ecf6782edaf16e7 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5959,9 +5959,10 @@ 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) {
+		reason = -reason;
 		goto discard;
-
+	}
 	tcp_rcv_rtt_measure_ts(sk, skb);
 
 	/* Process urgent data. */
-- 
2.36.0.rc0.470.gd361397f0d-goog

Re: [PATCH v2 net-next] tcp: fix signed/unsigned comparison

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by David S. Miller <davem@davemloft.net>:

On Sun, 17 Apr 2022 11:34:32 -0700 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> Kernel test robot reported:
> 
> smatch warnings:
> net/ipv4/tcp_input.c:5966 tcp_rcv_established() warn: unsigned 'reason' is never less than zero.
> 
> [...]

Here is the summary with links:
  - [v2,net-next] tcp: fix signed/unsigned comparison
    https://git.kernel.org/netdev/net-next/c/843f77407eeb

You are awesome, thank you!
-- 
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