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]

Date:	Wed, 9 Apr 2008 01:30:54 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	David Miller <davem@...emloft.net>, Jens Axboe <axboe@...nel.dk>,
	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 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.

I have an even deeper hack to fix this issue: put a list of pipe
structures as a lru.next pointer, mapping lock can guard processing...
Sounds scary, want to try.

-- 
	Evgeniy Polyakov
--
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