[patch 02/11] Fix the compat XFS_IOC_FSGEOMETRY_V1 ioctl

[Christoph Hellwig]

On Tue, Nov 18, 2008 at 10:44:03PM -0600, sandeen at sandeen.net wrote:
> This ioctl copies kernel data to the user, so we
> must have a compat helper to copy it out to the
> 32-bit structure; the current code had it backward,
> and translated the 32-bit arg to 64-bit, and called
> the native ioctl, which copied it back as if it were
> talking to 64-bit userspace.  Because the 64-bit arg
> has padding on the end on intel, I think this risked
> corruption in userspace..
> 
> Signed-off-by: Eric Sandeen <sandeen at sandeen.net>
> --

> +/* This handles a copy-out, where the 32-bit user struct lacks padding */
> +STATIC int
> +xfs_ioc_fsgeometry_v1_compat(
> +	xfs_mount_t		*mp,

	struct xfs_mount	*mp,

please

> +	void			__user *arg)
>  {
> +	xfs_fsop_geom_v1_t	fsgeo;
> +	int			error;
>  
> +	error = xfs_fs_geometry(mp, (xfs_fsop_geom_t *)&fsgeo, 3);
> +	if (error)
> +		return -error;
> +
> +	if (copy_to_user(arg, &fsgeo, sizeof(struct compat_xfs_fsop_geom_v1)))
>  		return -XFS_ERROR(EFAULT);
> +	return 0;

Any reason you only allocate a xfs_fsop_geom_v1_t on stack?  Just
allocating a xfs_fsop_geom_t even if you don't use it would be cleaner.