Re: [PATCH v4] fs: forbid invalid project ID

["Darrick J. Wong" <djwong@kernel.org>]

On Sat, Jul 10, 2021 at 10:39:59PM +0800, Wang Shilong wrote:
> From: Wang Shilong <wshilong@ddn.com>
> 
> fileattr_set_prepare() should check if project ID
> is valid, otherwise dqget() will return NULL for
> such project ID quota.
> 
> Signed-off-by: Wang Shilong <wshilong@ddn.com>
> ---
> v3->v3:
> only check project Id if caller is allowed
> to change and being changed.
> 
> v2->v3: move check before @fsx_projid is accessed
> and use make_kprojid() helper.
> 
> v1->v2: try to fix in the VFS
>  fs/ioctl.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 1e2204fa9963..d4fabb5421cd 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -817,6 +817,14 @@ static int fileattr_set_prepare(struct inode *inode,
>  		if ((old_ma->fsx_xflags ^ fa->fsx_xflags) &
>  				FS_XFLAG_PROJINHERIT)
>  			return -EINVAL;
> +	} else {
> +		/*
> +		 * Caller is allowed to change the project ID. If it is being
> +		 * changed, make sure that the new value is valid.
> +		 */
> +		if (old_ma->fsx_projid != fa->fsx_projid &&
> +		    !projid_valid(make_kprojid(&init_user_ns, fa->fsx_projid)))
> +			return -EINVAL;

Hmm, for XFS this is sort of a userspace-breaking change in the sense
that (technically) we've never rejected -1 before.  xfs_quota won't have
anything to do with that, and (assuming I read the helper/macro
gooeyness correctly) the vfs quota code won't either, so

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

>  	}
>  
>  	/* Check extent size hints. */
> -- 
> 2.27.0
>