Re: [PATCH 2/2] VFS: add common error checks to lookup_one_qstr_excl()

[Al Viro <viro@zeniv.linux.org.uk>]

On Fri, Feb 07, 2025 at 02:36:48PM +1100, NeilBrown wrote:
> @@ -1690,6 +1692,15 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name,
>  		dput(dentry);
>  		dentry = old;
>  	}
> +found:

... and if ->lookup() returns an error, this will blow up (as bot has just
reported).

> +	if (d_is_negative(dentry) && !(flags & LOOKUP_CREATE)) {
> +		dput(dentry);
> +		return ERR_PTR(-ENOENT);
> +	}
> +	if (d_is_positive(dentry) && (flags & LOOKUP_EXCL)) {
> +		dput(dentry);
> +		return ERR_PTR(-EEXIST);
> +	}


> @@ -4077,27 +4084,13 @@ static struct dentry *filename_create(int dfd, struct filename *name,
>  	 * '/', and a directory wasn't requested.
>  	 */
>  	if (last.name[last.len] && !want_dir)
> -		create_flags = 0;
> +		create_flags &= ~LOOKUP_CREATE;

See the patch I've posted in earlier thread; the entire "strip LOOKUP_CREATE"
thing is wrong.