linux-ext4 - Re: [BUG] invalid superblock checksum possibly due to race

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] [day] [month] [year] [list]

Message-ID: <20200701162248.GA4355@quack2.suse.cz>
Date:   Wed, 1 Jul 2020 18:22:48 +0200
From:   Jan Kara <jack@...e.cz>
To:     Costa Sapuntzakis <costa@...estorage.com>
Cc:     Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org
Subject: Re: [BUG] invalid superblock checksum possibly due to race

Hello!

On Tue 30-06-20 11:34:49, Costa Sapuntzakis wrote:
> > Yes, probably ext4_superblock_csum_set() should use
> >
> > lock_buffer(EXT4_SB(sb)->s_sbh)
> >
> > to synchronize updating of superblock checksum. Will you send a patch?
> 
> Yes. I will send a patch.

Thanks!

> I noticed lock_buffer can sleep. That would seem to imply to me that
> lock_buffer can be held across I/Os.
> I worry that this will occasionally significantly slow down this code
> path compared to what it used to be.  Are there any things
> about the way ext4 uses buffers that makes this less of a concern?

Yes, buffer lock is a sleeping lock but that's the lock we usually use to
protect consistency of buffer contents. So I prefer to use that lock unless
we have definitive performance data showing we need something more
clever...

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR