netdev - Re: [PATCH RFC net-next 1/6] sock: MSG_PEEK support for sk_error

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:   Thu, 18 Jan 2018 18:20:23 -0500
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>, rds-devel@....oracle.com,
        santosh.shilimkar@...cle.com
Subject: Re: [PATCH RFC net-next 1/6] sock: MSG_PEEK support for
 sk_error_queue

On (01/18/18 18:09), Willem de Bruijn wrote:
> If that is true in general for PF_RDS, then it is a reasonable approach.
> How about treating it as a (follow-on) optimization path. Opportunistic
> piggybacking of notifications on data reads is more widely applicable.

sounds good.

> > that's similar to what I have, except that it does not have the
> > MSG_PEEK part (you'd need to enforce that the data portion
> > is upper-bounded, and that the application has the responsibility
> > of sending down "enough" buffer with recvmsg).
> 
> Right. I think that an upper bound is the simplest solution here.
> 
> By the way, if you allocate an skb immediately on page pinning, then
> there are always sufficient skbs to store all notifications. On errqueue
> enqueue just drop the new skb and copy its notification to the body of
> the skb already on the queue, if one exists and it has room. That is
> essentially what the tcp zerocopy code does with the [data, info] range.

ok, I'll give that a shot (I'm working through the other review comments
as well)

fwiw, the data-corruption issue I mentioned turned out to be a day-one
bug in rds-tcp (patched in http://patchwork.ozlabs.org/patch/863183/). 
The buffer reaping with zcopy (and aggressiveness of rds-stress) brought
this one out..

--Sowmini