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Re: [PATCH 6/9] xfs: XFS_IOCTL_SETXATTR can run in user namespaces

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [PATCH 6/9] xfs: XFS_IOCTL_SETXATTR can run in user namespaces
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Thu, 29 Jan 2015 10:35:15 -0500
Cc: xfs@xxxxxxxxxxx, iustin@xxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1422328486-24661-7-git-send-email-david@xxxxxxxxxxxxx>
References: <1422328486-24661-1-git-send-email-david@xxxxxxxxxxxxx> <1422328486-24661-7-git-send-email-david@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.23 (2014-03-12)
On Tue, Jan 27, 2015 at 02:14:43PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
> 
> Currently XFS_IOCTL_SETXATTR will fail if run in a user namespace as
> it it not allowed to change project IDs. The current code, however,
> also prevents any other change being made as well, so things like
> extent size hints cannot be set in user namespaces. This is wrong,
> so only disallow access to project IDs and related flags from inside
> the init namespace.
> 
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> ---
>  fs/xfs/xfs_ioctl.c | 22 +++++++++++++---------
>  1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 563d2b4..ae6e1e3 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1120,6 +1120,19 @@ xfs_ioctl_setattr(
>               return -EINVAL;
>  
>       /*
> +      * Project Quota ID state is only allowed to change from within the init
> +      * namespace. Enforce that restriction only if we are trying to change
> +      * the quota ID state. Everything else is allowed in user namespaces.
> +      */
> +     if (current_user_ns() != &init_user_ns) {
> +             if (xfs_get_projid(ip) != fa->fsx_projid)
> +                     return -EINVAL;
> +             if ((fa->fsx_xflags & XFS_XFLAG_PROJINHERIT) ^
> +                 (ip->i_d.di_flags & XFS_DIFLAG_PROJINHERIT))

Why not use != here? Looks fine, anyways:

Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

> +                     return -EINVAL;
> +     }
> +
> +     /*
>        * If disk quotas is on, we make sure that the dquots do exist on disk,
>        * before we start any other transactions. Trying to do this later
>        * is messy. We don't care to take a readlock to look at the ids
> @@ -1139,15 +1152,6 @@ xfs_ioctl_setattr(
>       if (IS_ERR(tp))
>               return PTR_ERR(tp);
>  
> -     /*
> -      * Do a quota reservation only if projid is actually going to change.
> -      * Only allow changing of projid from init_user_ns since it is a
> -      * non user namespace aware identifier.
> -      */
> -     if (current_user_ns() != &init_user_ns) {
> -             code = -EINVAL;
> -             goto error_return;
> -     }
>  
>       if (XFS_IS_QUOTA_RUNNING(mp) && XFS_IS_PQUOTA_ON(mp) &&
>           xfs_get_projid(ip) != fa->fsx_projid) {
> -- 
> 2.0.0
> 
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