[Hardy, Maverick] [CVE-2011-0463] [PATCH 1/1] Treat writes as new when holes span across page boundaries, CVE-2011-0463

[Leann Ogasawara]

On Tue, 2011-04-26 at 09:00 -0700, Brad Figg wrote:
> From: Goldwyn Rodrigues <rgoldwyn at gmail.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/770483
> 
> CVE-2011-0463
> 
> When a hole spans across page boundaries, the next write forces
> a read of the block. This could end up reading existing garbage
> data from the disk in ocfs2_map_page_blocks. This leads to
> non-zero holes. In order to avoid this, mark the writes as new
> when the holes span across page boundaries.
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn at suse.de>
> Signed-off-by: jlbec <jlbec at evilplan.org>
> 
> (cherry-pick of commit 272b62c1f0f6f742046e45b50b6fec98860208a0)
> Signed-off-by: Brad Figg <brad.figg at canonical.com>

Acked-by: Leann Ogasawara <leann.ogasawara at canonical.com>

> ---
>  fs/ocfs2/aops.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
> index 0d44b77..b5d7fb9 100644
> --- a/fs/ocfs2/aops.c
> +++ b/fs/ocfs2/aops.c
> @@ -1015,6 +1015,12 @@ static int ocfs2_prepare_page_for_write(struct inode *inode, u64 *p_blkno,
>  	ocfs2_figure_cluster_boundaries(OCFS2_SB(inode->i_sb), cpos,
>  					&cluster_start, &cluster_end);
>  
> +	/* treat the write as new if the a hole/lseek spanned across
> +	 * the page boundary.
> +	 */
> +	new = new | ((i_size_read(inode) <= page_offset(page)) &&
> +			(page_offset(page) <= user_pos));
> +
>  	if (page == wc->w_target_page) {
>  		map_from = user_pos & (PAGE_CACHE_SIZE - 1);
>  		map_to = map_from + user_len;
> -- 
> 1.7.0.4
> 
>