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	Wed, 12 Feb 2025 03:16:08 +0000
Date: Wed, 12 Feb 2025 03:16:08 +0000
From: Al Viro <viro@zeniv.linux.org.uk>
To: NeilBrown <neilb@suse.de>
Cc: Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Danilo Krummrich <dakr@kernel.org>,
	Kent Overstreet <kent.overstreet@linux.dev>,
	Trond Myklebust <trondmy@kernel.org>,
	Anna Schumaker <anna@kernel.org>,
	Namjae Jeon <linkinjeon@kernel.org>,
	Steve French <sfrench@samba.org>,
	Sergey Senozhatsky <senozhatsky@chromium.org>,
	Tom Talpey <tom@talpey.com>, Paul Moore <paul@paul-moore.com>,
	Eric Paris <eparis@redhat.com>, linux-kernel@vger.kernel.org,
	linux-bcachefs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org,
	audit@vger.kernel.org
Subject: Re: [PATCH 2/2] VFS: add common error checks to
 lookup_one_qstr_excl()
Message-ID: <20250212031608.GL1977892@ZenIV>
References: <20250207034040.3402438-1-neilb@suse.de>
 <20250207034040.3402438-3-neilb@suse.de>
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Sender: Al Viro <viro@ftp.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.