netdev - Re: [BUG?] tcp: potential bug in tcp_is_sackblock

lists.openwall.net		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 linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 9 Sep 2011 11:03:58 +0300 (EEST)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	"Yan, Zheng" <zheng.z.yan@...el.com>
cc:	Herbert Xu <herbert@...dor.hengli.com.au>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"eric.dumazet@...il.com" <eric.dumazet@...il.com>,
	"sfr@...b.auug.org.au" <sfr@...b.auug.org.au>
Subject: Re: [BUG?] tcp: potential bug in tcp_is_sackblock_valid()

On Fri, 9 Sep 2011, Yan, Zheng wrote:

> On 09/09/2011 09:54 AM, Herbert Xu wrote:
> > On Fri, Sep 09, 2011 at 09:45:52AM +0800, Yan, Zheng wrote:
> >> I found a check in tcp_is_sackblock_valid() is suspicious. It against
> >> its comment and RFC. I think the correct check should be:
> >> ---
> >> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> >> index 385c470..a5d01b1 100644
> >> --- a/net/ipv4/tcp_input.c
> >> +++ b/net/ipv4/tcp_input.c
> >> @@ -1124,7 +1124,7 @@ static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
> >>                 return 0;
> >>  
> >>         /* ...Then it's D-SACK, and must reside below snd_una completely */
> >> -       if (!after(end_seq, tp->snd_una))
> >> +       if (after(end_seq, tp->snd_una))
> >>                 return 0;
> >>  
> >>         if (!before(start_seq, tp->undo_marker))
> >> ---
> >>
> >> I also checked /proc/net/netstat of my laptop, found TCPDSACKIgnoredOld
> >> field is not zero. Maybe it's caused by the bug.

Hmm, some Ignored I was expecting to see even when nothing was wrong but I 
think it might have been the other counter... too long time already passed 
to remember all the details I've been thinking.

> > Yes this looks like a typo.  Please resend your patch with a
> > description and signed-off-by line.
> 
> I think the bug has a big influence on tcp DSACKs. It's better to
> leave it to people who fully understand tcp code.

Indeed, it looks like a double negative error.

-- 
 i.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html