linux-kernel - Re: [BUG] packet loss with PROVE

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]

Message-ID: <20160322091656.GA11313@localhost>
Date:	Tue, 22 Mar 2016 09:16:56 +0000
From:	Chris Bainbridge <chris.bainbridge@...il.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
	mchehab@...radead.org, markus@...ppelsdorf.de, tony.luck@...el.com
Subject: Re: [BUG] packet loss with PROVE_LOCKING, bisected to EDAC fix

On Tue, Mar 22, 2016 at 06:31:54AM +0100, Borislav Petkov wrote:
> On Mon, Mar 21, 2016 at 09:42:09PM +0000, Chris Bainbridge wrote:
> > Hi,
> > 
> > I was testing something on an old server (Dell T105 opteron) and noticed
> > packet loss after updating the kernel from 3.10 to 4.5. The test was:
> > 
> > On Dell run: iperf -s
> > On another system: iperf3 -c dell -u -b 20M -l 1k -t 1000
> > 
> > This sends a 20mbit UDP stream to the Dell. It works fine normally (0%
> > packet loss), but when CONFIG_PROVE_LOCKING is enabled there is high
> > (35%) packet loss. (DEBUG_LOCKDEP also seems to cause packet loss)
> > 
> > The packet loss bisected back to:
> > 
> > commit 88d84ac97378c2f1d5fec9af1e8b7d9a662d6b00
> > Author: Borislav Petkov <bp@...e.de>
> > Date:   Fri Jul 19 12:28:25 2013 +0200
> > 
> >     EDAC: Fix lockdep splat
> 
> Hmm, how would that cause a packet loss?!

Good question. The patch looks pretty innocuous but it is for a lockdep
issue and the bug only appears when lockdep config options are enabled.
Could it somehow have broken a lock used to synchronise packet rx?

> > I have confirmed that the commit preceding this (v3.11-rc1) is fine and
> > that 88d84a introduced the bug.
> 
> Did you revert this commit ontop of 4.5 and reproduce again? Do you see
> the same packet loss?

Reverting over 4.5 does fix the packet loss issue.

> What kind of hw is that target system, can you send full dmesg and
> .config?

It is https://www.suse.com/yes/123682.htm with a slightly faster CPU
(Opteron 1212 2Ghz) and 4GB RAM.

dmesg and .config attached.

View attachment "config-t105-4.5" of type "text/plain" (111242 bytes)

View attachment "dmesg-dell" of type "text/plain" (43672 bytes)