From: Frans Pop <elendil@planet•nl>
To: "Ilpo Järvinen" <ilpo.jarvinen@helsinki•fi>
Cc: Matthias Andree <matthias.andree@gmx•de>,
David Miller <davem@davemloft•net>,
Netdev <netdev@vger•kernel.org>
Subject: Re: Strange Application bug, race in MSG_PEEK complaints (was: Bug#513695: fetchmail: race in MSG_PEEK)
Date: Thu, 7 May 2009 19:16:56 +0200 [thread overview]
Message-ID: <200905071916.57903.elendil@planet.nl> (raw)
In-Reply-To: <Pine.LNX.4.64.0905070931590.12068@wrl-59.cs.helsinki.fi>
On Thursday 07 May 2009, Ilpo Järvinen wrote:
> On Thu, 7 May 2009, Matthias Andree wrote:
> > I've applied the following patch to net/ipv4/tcp.c for the kernel
> > running on my server (2.6.29-rc8):
> > @@ -1499,8 +1499,9 @@ do_prequeue:
> > }
> > if ((flags & MSG_PEEK) && peek_seq != tp->copied_seq) {
> > if (net_ratelimit())
> > - printk(KERN_DEBUG "TCP(%s:%d): Application bug, race in MSG_PEEK.\n",
> > - current->comm, task_pid_nr(current));
> > + printk(KERN_DEBUG "TCP(%s:%d): Application bug, race in MSG_PEEK: %x, %x.\n",
> > + current->comm, task_pid_nr(current)),
> > + peek_seq, tp->copied_seq;
>
> I cannot resist myself from noting that this certainly wasn't the patch
> one got those printks below... It might happily compile though :-).
Can you please elaborate why you think that? It may be horribly broken
(I've never claimed to be a C coder, and probably never will), but it
also really is the patch that generates the printks...
> > peek_seq = tp->copied_seq;
> > }
> > continue;
> >
> > So, the values you see at the end of the warning are peek_seq and
> > tp->copied_seq. This gives messages like:
> > kernel: TCP(fetchmail:9311): Application bug, race in MSG_PEEK: 156233, 16a.
> > kernel: TCP(fetchmail:9311): Application bug, race in MSG_PEEK: 71259ac8, 5b4.
> > kernel: TCP(fetchmail:31216): Application bug, race in MSG_PEEK: 833fe5, c0.
[...]
> What would you think about the following, untested patch... I suppose
> it is enough to capture the racy situations except with that crazy urg
> hole, grr (I suppose that will need just another variable to do the
> offset of one).
I'll give your patch a try and report back.
Thanks,
FJP
next prev parent reply other threads:[~2009-05-07 17:16 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200902262310.12791.elendil@planet.nl>
[not found] ` <200903091749.50818.elendil@planet.nl>
[not found] ` <op.uqjiqsol1e62zd@merlin.emma.line.org>
[not found] ` <200903141900.14498.elendil@planet.nl>
2009-05-06 16:15 ` Strange Application bug, race in MSG_PEEK complaints (was: Bug#513695: fetchmail: race in MSG_PEEK) Matthias Andree
2009-05-06 23:02 ` Matthias Andree
2009-05-07 6:48 ` Ilpo Järvinen
2009-05-07 17:16 ` Frans Pop [this message]
2009-05-07 18:48 ` Ilpo Järvinen
2009-05-07 20:43 ` Frans Pop
2009-05-09 18:14 ` Frans Pop
2009-05-11 6:32 ` [PATCH v2] tcp: fix MSG_PEEK race check Ilpo Järvinen
2009-05-11 12:50 ` Frans Pop
2009-05-11 13:32 ` Ilpo Järvinen
2009-05-11 13:54 ` Frans Pop
2009-05-11 14:57 ` Ilpo Järvinen
2009-05-17 22:31 ` David Miller
2009-05-18 8:02 ` Matthias Andree
2009-05-17 22:41 ` David Miller
2009-05-18 7:24 ` Ilpo Järvinen
2009-05-18 15:34 ` Matthias Andree
2009-05-18 22:04 ` David Miller
2009-05-19 4:33 ` Ilpo Järvinen
2009-05-19 4:40 ` David Miller
2009-05-19 9:05 ` Matthias Andree
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