linux-ext4 - Re: [PATCH 2/4] ext4: Fix ext4_writepages() in presence of truncate

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:	Sat, 17 Aug 2013 10:08:11 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Jan Kara <jack@...e.cz>
Cc:	linux-ext4@...r.kernel.org, Dave Jones <davej@...hat.com>,
	Zheng Liu <gnehzuil.liu@...il.com>
Subject: Re: [PATCH 2/4] ext4: Fix ext4_writepages() in presence of truncate

On Mon, Aug 05, 2013 at 03:52:22PM +0200, Jan Kara wrote:
> Inode size can arbitrarily change while writeback is in progress. When
> ext4_writepages() has prepared a long extent for mapping and truncate
> then reduces i_size, mpage_map_and_submit_buffers() will always map just
> one buffer in a page instead of all of them due to lblk < blocks check.
> So we end up not using all blocks we've allocated (thus leaking them)
> and also delalloc accounting goes wrong manifesting as a warning like:
> 
> ext4_da_release_space:1333: ext4_da_release_space: ino 12, to_free 1
> with only 0 reserved data blocks
> 
> Note that the problem can happen only when blocksize < pagesize because
> otherwise we have only a single buffer in the page.
> 
> Fix the problem by removing the size check from the mapping loop. We
> have an extent allocated so we have to use it all before checking for
> i_size. We also rename add_page_bufs_to_extent() to
> mpage_process_page_bufs() and make that function submit the page for IO
> if all buffers (upto EOF) in it are mapped.
> 
> Reported-by: Dave Jones <davej@...hat.com>
> Reported-by: Zheng Liu <gnehzuil.liu@...il.com>
> Signed-off-by: Jan Kara <jack@...e.cz>

Thanks, applied.

					- Ted
--
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