linux-kernel - Re: Revert "gro: Fix legacy path napi

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: <20090325.202050.08183381.davem@davemloft.net>
Date:	Wed, 25 Mar 2009 20:20:50 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	jarkao2@...il.com, mingo@...e.hu, r.schwebel@...gutronix.de,
	torvalds@...ux-foundation.org, blaschka@...ux.vnet.ibm.com,
	tglx@...utronix.de, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: Revert "gro: Fix legacy path napi_complete crash",

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Thu, 26 Mar 2009 10:41:29 +0800

> On Wed, Mar 25, 2009 at 11:54:56PM +0100, Jarek Poplawski wrote:
> > 
> > Of course it's too late for verifying this now, but (for the future)
> > I think, this scenario could be considered:
> > 
> > process_backlog()			netif_rx()
> > 
> > if (!skb)
> > local_irq_enable()
> > 					if (queue.qlen) //NO
> > 					napi_schedule() //NOTHING
> > 					__skb_queue_tail() //qlen > 0
> > napi_complete()
> > ...					...
> > 					Every next netif_rx() sees
> > 					qlen > 0, so napi is never
> > 					scheduled again.
> > 
> > Then, something like this might work...
> 
> Yes this is why my original patch that started all this is broken.
> However, this doesn't apply to my patch that open-codes __napi_complete.

There is still a difference compared to your fix Herbert.  Jarek's
patch flushes GRO first before the unlink.

I still believe that's critical, although like you I can't pinpoint
why.

I know that GRO ought to be disabled here, but what if for some reason
it isn't? :-)

Adam Richter has successfully tested Jarek's variant, and if Ingo's
tests show that it makes his problem go away too then I'm definitely
going with Jarek's patch.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/