linux-ext4 - Re: [RFC, PATCH 6/6] ext3: do not write to the disk when mounting a dirty read-only filesystem

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 12 Mar 2008 02:42:46 +0000
From:	"Duane Griffin" <duaneg@...da.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Andreas Dilger <adilger@....com>, Duane Griffin <duaneg@...da.com>,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	Theodore Tso <tytso@....edu>, sct@...hat.com,
	akpm@...ux-foundation.org
Subject: Re: [RFC, PATCH 6/6] ext3: do not write to the disk when mounting
	a dirty read-only filesystem

On Tue, Mar 11, 2008 at 04:11:23PM +0100, Jan Kara wrote:
>   Actually, this is nastier than it looks - currently fs, asks
> ext3_sb_getblk() for block 'a' and it gets buffer head with b_blocknr == 'b'
> instead.

Note that it will be a different device as well, in the case of an
external journal.

> So when remounting you'd have to rewrite these buffers with
> original block numbers which is not really possible. So I think
> remapping will have to be solved differently, like providing buffer
> head with correct b_blocknr but taking care when reading data to it and
> reading them from elsewhere. Actually, this has to be done anyway
> because JBD escapes data in the journal and you have to do unescaping
> when reading data...

Hmm, I'll think about this and try to get something working. As a quick
proof-of-concept hack, getting both buffers then overwriting the fs
block's data with the unescaped journal data should do the trick, right?

Cheers,
Duane.

-- 
"I never could learn to drink that blood and call it wine" - Bob Dylan
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html