Re: [RFC PATCH v2 1/3] xfs: Align compat attrlist_by_handle with native implementation.

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Dec 14, 2018 at 08:22:57PM -0500, Nick Bowler wrote:
> While inspecting the ioctl implementations, I noticed that the compat
> implementation of XFS_IOC_ATTRLIST_BY_HANDLE does not do exactly the
> same thing as the native implementation.  Specifically, the "cursor"
> does not appear to be written out to userspace on the compat path,
> like it is on the native path.
> 
> This adjusts the compat implementation to copy out the cursor just
> like the native implementation does.  The attrlist cursor does not
> require any special compat handling.  This fixes xfstests xfs/269
> on both IA-32 and x32 userspace, when running on an amd64 kernel.

Craaap, I forgot that when I fixed the native attrlist_by_handle. :(

> Signed-off-by: Nick Bowler <nbowler@draconx.ca>

Fixes: 0facef7fb053b ("xfs: in _attrlist_by_handle, copy the cursor back to userspace")
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/xfs_ioctl32.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c
> index fba115f4103a..4c34efcbf7e8 100644
> --- a/fs/xfs/xfs_ioctl32.c
> +++ b/fs/xfs/xfs_ioctl32.c
> @@ -336,6 +336,7 @@ xfs_compat_attrlist_by_handle(
>  {
>  	int			error;
>  	attrlist_cursor_kern_t	*cursor;
> +	compat_xfs_fsop_attrlist_handlereq_t __user *p = arg;
>  	compat_xfs_fsop_attrlist_handlereq_t al_hreq;
>  	struct dentry		*dentry;
>  	char			*kbuf;
> @@ -370,6 +371,11 @@ xfs_compat_attrlist_by_handle(
>  	if (error)
>  		goto out_kfree;
>  
> +	if (copy_to_user(&p->pos, cursor, sizeof(attrlist_cursor_kern_t))) {
> +		error = -EFAULT;
> +		goto out_kfree;
> +	}
> +
>  	if (copy_to_user(compat_ptr(al_hreq.buffer), kbuf, al_hreq.buflen))
>  		error = -EFAULT;
>  
> -- 
> 2.16.1
>