netdev - Re: [take 2] Fix for the fundamental network/block layer race in sendfile().

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: <20080409113321.GK12774@kernel.dk>
Date:	Wed, 9 Apr 2008 13:33:21 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	Eric Dumazet <dada1@...mosbay.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [take 2] Fix for the fundamental network/block layer race in sendfile().

On Wed, Apr 09 2008, Evgeniy Polyakov wrote:
> On Tue, Apr 08, 2008 at 09:26:52PM +0400, Evgeniy Polyakov (johnpol@....mipt.ru) wrote:
> > >    Unless I mistaken, you store in page->lru.next some info to find 
> > > your pipe pointer, assuming it is unique for this page.
> > > 
> > > What happens if two threads are doing a splice()/sendfile() using the 
> > > same underlying (source) file (and same pages in this file)
> > 
> > Page will be referenced twice (for each thread) and each thread will
> > have own pipe_inode_info structure, so each one will sleep on own wait
> > queue and will be awakened separately, where its release counter will be
> > dropped.
> 
> I was wrong, here will be a problem - page can be shared between multiple
> threads, since it is unlocked after putting it into page cache, so it is
> not allowed to put into it some per-thread private data.

Threads or not, it does not matter. Even simpler, the same page could be
in multiple pipes. So that trick definitely will not work at all.

-- 
Jens Axboe

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html