linux-ext4 - Re: [PATCH] ext3: prevent reread after write IO error

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:	Thu, 14 Jan 2010 18:05:32 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
Cc:	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andreas Dilger <adilger@....com>,
	"Theodore Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>,
	Nick Piggin <npiggin@...e.de>,
	dle-develop@...ts.sourceforge.net,
	Satoshi OSHIMA <satoshi.oshima.fk@...achi.com>
Subject: Re: [PATCH] ext3: prevent reread after write IO error

Hi,

Hidehiro Kawai wrote:

> This patch fixes the similar bug fixed by commit 95450f5a.
> 
> If a directory is modified, its data block is journaled as metadata
> and finally written back to the right place.  Now, we assume a
> transient write erorr happens on that writeback.  Uptodate flag of
> the buffer is cleared by write error, so next access on the buffer
> causes a reread from disk.  This means it breaks the filesystems
> consistency.

After sending this patch, I noticed that I have to deal with
the bh_uptodate_or_lock() case as well.  Actually, I confirmed
a data block sharing happens between two inodes. Allocate a new
block, then modified bitmap goes to the fs, but it fails due to
a transient IO error.  Next access on the bitmap buffer cause a
reread from disk.  As a result, the allocated block becomes 
a FREE block!  So this block can be shared by different two inodes.

I'll send the revised version later.

Thanks,
-- 
Hidehiro Kawai
Hitachi, Systems Development Laboratory
Linux Technology Center

--
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