From: Frans Pop <elendil@planet•nl>
To: "Ilpo Järvinen" <ilpo.jarvinen@helsinki•fi>
Cc: Matthias Andree <matthias.andree@gmx•de>,
Netdev <netdev@vger•kernel.org>,
David Miller <davem@davemloft•net>
Subject: Re: [PATCH v2] tcp: fix MSG_PEEK race check
Date: Mon, 11 May 2009 14:50:05 +0200 [thread overview]
Message-ID: <200905111450.06749.elendil@planet.nl> (raw)
In-Reply-To: <Pine.LNX.4.64.0905110926520.10047@wrl-59.cs.helsinki.fi>
On Monday 11 May 2009, Ilpo Järvinen wrote:
> I took my time to fix the urg_hole madness too. The patch below.
Hmm. I wonder if it wouldn't be better to keep the two issues separate.
The initial patch is a clear regression fix (4 people have reported it
against fetchmail for Debian). The URG part is IMO a separate issue which
I at least have never seen in practice.
And my Tested-by doesn't cover the additional change either.
That said, I have added the URG change (as an incremental patch) in my
local git repo and will give it a go when I next build a kernel (may take
a week). I don't expect to be able to confirm it fixes the URG race, but
I can at least check that it doesn't cause any false messages with my
(spectacularly unspectacular) network traffic. I'll report the result.
> --
> [PATCH v2] tcp: fix MSG_PEEK race check
>
> Commit 518a09ef11 (tcp: Fix recvmsg MSG_PEEK influence of
> blocking behavior) lets the loop run longer than the race check
> did previously expect, so we need to be more careful with this
> check and consider the work we have been doing.
>
> I tried my best to deal with urg hole madness too which happens
> here:
> if (!sock_flag(sk, SOCK_URGINLINE)) {
> ++*seq;
> ...
> by using additional offset by one but I certainly have very
> little interest in testing that part.
>
> Signed-off-by: Ilpo J?rvinen <ilpo.jarvinen@helsinki•fi>
> Tested-by: Frans Pop <elendil@planet•nl>
> ---
> net/ipv4/tcp.c | 5 ++++-
> 1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 1d7f49c..7a0f0b2 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -1321,6 +1321,7 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock
> *sk, struct msghdr *msg, struct task_struct *user_recv = NULL;
> int copied_early = 0;
> struct sk_buff *skb;
> + u32 urg_hole = 0;
>
> lock_sock(sk);
>
> @@ -1532,7 +1533,8 @@ do_prequeue:
> }
> }
> }
> - if ((flags & MSG_PEEK) && peek_seq != tp->copied_seq) {
> + if ((flags & MSG_PEEK) &&
> + (peek_seq - copied - urg_hole != 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));
> @@ -1553,6 +1555,7 @@ do_prequeue:
> if (!urg_offset) {
> if (!sock_flag(sk, SOCK_URGINLINE)) {
> ++*seq;
> + urg_hole++;
> offset++;
> used--;
> if (!used)
next prev parent reply other threads:[~2009-05-11 12:50 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
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 [this message]
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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