lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Thu, 24 May 2012 05:51:37 +0200
From:	Eric Dumazet <>
To:	Sergio Correia <>, David Miller <>
Subject: [PATCH] tcp: take care of overlaps in tcp_try_coalesce()

From: Eric Dumazet <>

On Thu, 2012-05-24 at 00:21 -0300, Sergio Correia wrote:

> With your patch applied, the warning hasn't shown up in the last
> hours. Without it, dmesg would have been completely taken by them by
> now.
> I might be able to reproduce your test setup tomorrow, and if so, I will retest.

I am going to send an official patch right now.

My own testings confirmed the bug origin and I am confident the patch is

Thanks !

[PATCH] tcp: take care of overlaps in tcp_try_coalesce()

Sergio Correia reported following warning :

WARNING: at net/ipv4/tcp.c:1301 tcp_cleanup_rbuf+0x4f/0x110()

WARN(skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq),
     "cleanup rbuf bug: copied %X seq %X rcvnxt %X\n",
     tp->copied_seq, TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt);

It appears TCP coalescing, and more specifically commit b081f85c297
(net: implement tcp coalescing in tcp_queue_rcv()) should take care of
possible segment overlaps in receive queue. This was properly done in
the case of out_or_order_queue by the caller.

For example, segment at tail of queue have sequence 1000-2000, and we
add a segment with sequence 1500-2500.
This can happen in case of retransmits.

In this case, just don't do the coalescing.

Reported-by: Sergio Correia <>
Signed-off-by: Eric Dumazet <>
Tested-by: Sergio Correia <>
 net/ipv4/tcp_input.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index cfa2aa1..b224eb8 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4555,6 +4555,11 @@ static bool tcp_try_coalesce(struct sock *sk,
 	if (tcp_hdr(from)->fin)
 		return false;
+	/* Its possible this segment overlaps with prior segment in queue */
+	if (TCP_SKB_CB(from)->seq != TCP_SKB_CB(to)->end_seq)
+		return false;
 	if (!skb_try_coalesce(to, from, fragstolen, &delta))
 		return false;

To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists