Re: [PATCH v2] fs: forbid invalid project ID

[Dave Chinner <david@fromorbit.com>]

On Mon, Jun 28, 2021 at 08:38:01AM -0400, Wang Shilong wrote:
> 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>
> ---
> v1->v2: try to fix in the VFS
> ---
>  fs/ioctl.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 1e2204fa9963..5db5b218637b 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -845,6 +845,9 @@ static int fileattr_set_prepare(struct inode *inode,
>  	if (fa->fsx_cowextsize == 0)
>  		fa->fsx_xflags &= ~FS_XFLAG_COWEXTSIZE;
>  
> +	if (!projid_valid(KPROJIDT_INIT(fa->fsx_projid)))
> +		return -EINVAL;

This needs to go further up in this function in the section where
project IDs passed into this function are validated. Projids are
only allowed to be changed when current_user_ns() == &init_user_ns,
so this needs to be associated with that verification context.

This check should also use make_kprojid(), please, not open code
KPROJIDT_INIT.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com