Re: [PATCH 8/9] overlayfs: Dilute permission checks on lower only if not special file

[Miklos Szeredi]

On Wed, Jul 13, 2016 at 4:44 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote:
> Right now if file is on lower/, we remove MAY_WRITE/MAY_APPEND bits from
> mask as lower/ will never be written and file will be copied up. But this
> is not true for special files. These files are not copied up and are
> opened in place. So don't dilute the checks for these types of files.

Pushed this one as well.

Miklos

>
> Reported-by: Dan Walsh <dwalsh@xxxxxxxxxx>
> Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
> ---
>  fs/overlayfs/inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index 66f42f5..6d9d86e 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -140,7 +140,7 @@ int ovl_permission(struct inode *inode, int mask)
>                 return err;
>
>         old_cred = ovl_override_creds(inode->i_sb);
> -       if (!is_upper)
> +       if (!is_upper && !special_file(realinode->i_mode))
>                 mask &= ~(MAY_WRITE | MAY_APPEND);
>         err = inode_permission(realinode, mask);
>         revert_creds(old_cred);
> --
> 2.7.4
>