Re: [PATCH] make new mount API honour SB_NOUSER (was Re: [PATCH] block: Avoid mounting the bdev pseudo-filesystem in userspace)

[Jan Kara]

On Tue 02-06-26 03:04:44, Al Viro wrote:
> one should *not* be allowed to mount one of those, new API or not.
> 
> Reported-by: Denis Arefev <arefev@xxxxxxxxx>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

Won't it make sense to actually check fc->sb_flags before we call
vfs_create_mount()? Otherwise it looks good to me.

								Honza

> ---
> [[ I still want to see the rest of the reproducer - report smells like a missing
> d_can_lookup() somewhere, on top of fsmount(2) bug]]
> diff --git a/fs/namespace.c b/fs/namespace.c
> index fe919abd2f01..17777c837683 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -4499,6 +4499,10 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
>  	new_mnt = vfs_create_mount(fc);
>  	if (IS_ERR(new_mnt))
>  		return PTR_ERR(new_mnt);
> +	if (new_mnt->mnt_sb->s_flags & SB_NOUSER) {
> +		mntput(new_mnt);
> +		return -EINVAL;
> +	}
>  	new_mnt->mnt_flags = mnt_flags;
>  
>  	new_path.dentry = dget(fc->root);
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR