Re: [PATCH 2/2] acct: block access to kernel internal filesystems

[Al Viro]

On Tue, Feb 11, 2025 at 06:16:00PM +0100, Christian Brauner wrote:
> There's no point in allowing anything kernel internal nor procfs or
> sysfs.

> +	/* Exclude kernel kernel internal filesystems. */
> +	if (file_inode(file)->i_sb->s_flags & (SB_NOUSER | SB_KERNMOUNT)) {
> +		kfree(acct);
> +		filp_close(file, NULL);
> +		return -EINVAL;
> +	}
> +
> +	/* Exclude procfs and sysfs. */
> +	if (file_inode(file)->i_sb->s_iflags & SB_I_USERNS_VISIBLE) {
> +		kfree(acct);
> +		filp_close(file, NULL);
> +		return -EINVAL;
> +	}

That looks like a really weird way to test it, especially the second
part...