ACK[B]: [SRU][X/A/B][PATCH 1/1] xfs: set format back to extents if xfs_bmap_extents_to_btree

[Kleber Souza]

On 07/06/18 07:33, Khalid Elmously wrote:
> From: Eric Sandeen <sandeen at redhat.com>
> 
> CVE-2018-10323
> 
> If xfs_bmap_extents_to_btree fails in a mode where we call
> xfs_iroot_realloc(-1) to de-allocate the root, set the
> format back to extents.
> 
> Otherwise we can assume we can dereference ifp->if_broot
> based on the XFS_DINODE_FMT_BTREE format, and crash.
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199423
> Signed-off-by: Eric Sandeen <sandeen at redhat.com>
> Reviewed-by: Christoph Hellwig <hch at lst.de>
> Reviewed-by: Darrick J. Wong <darrick.wong at oracle.com>
> Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
> (cherry-picked from 2c4306f719b083d17df2963bc761777576b8ad1b)
> Signed-off-by: Khalid Elmously <khalid.elmously at canonical.com>
> ---
>  fs/xfs/libxfs/xfs_bmap.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 1bddbba6b80c..c756db755a5a 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -725,12 +725,16 @@ xfs_bmap_extents_to_btree(
>  	*logflagsp = 0;
>  	if ((error = xfs_alloc_vextent(&args))) {
>  		xfs_iroot_realloc(ip, -1, whichfork);
> +		ASSERT(ifp->if_broot == NULL);
> +		XFS_IFORK_FMT_SET(ip, whichfork, XFS_DINODE_FMT_EXTENTS);
>  		xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
>  		return error;
>  	}
>  
>  	if (WARN_ON_ONCE(args.fsbno == NULLFSBLOCK)) {
>  		xfs_iroot_realloc(ip, -1, whichfork);
> +		ASSERT(ifp->if_broot == NULL);
> +		XFS_IFORK_FMT_SET(ip, whichfork, XFS_DINODE_FMT_EXTENTS);
>  		xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
>  		return -ENOSPC;
>  	}
> 

For Bionic only:

Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>