From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2EABFC433EF for ; Wed, 6 Apr 2022 11:25:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242060AbiDFL1E (ORCPT ); Wed, 6 Apr 2022 07:27:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51256 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241115AbiDFL0f (ORCPT ); Wed, 6 Apr 2022 07:26:35 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D309355CFE8; Wed, 6 Apr 2022 01:13:15 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 4DED31F38A; Wed, 6 Apr 2022 08:13:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1649232794; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/rBcyoDoTq/ouUuDrmZ5BU4RlZeCyQlpcb/fLfqi5+g=; b=dJ+xoXpY08wKZSxp4z1Y5Osm1Twl7YrbmzMZrDi+X2woMiKeABbNRwulYBc2qOF6dH3brs MNTVdkTWKIpEhYzVo45ZPk4swaf0E52Z+v/2uKVyVQI5xbozxEx46EpwHv1IkCHg1/P9MJ oeOBCZNuC7mWz+jnAtWnLkdd6TkHf0M= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1649232794; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/rBcyoDoTq/ouUuDrmZ5BU4RlZeCyQlpcb/fLfqi5+g=; b=+cHhjmj0LF7iVvf9KUfF3wuUVkHwKWOHOJ0OtTa9gm6FBswBsRelBd0noj2RXLYYVFYpeZ Z7ZFBZ+7OjnqgnCA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 1266A13A8E; Wed, 6 Apr 2022 08:13:14 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id Ik0hA5pLTWJeYAAAMHmgww (envelope-from ); Wed, 06 Apr 2022 08:13:14 +0000 Date: Wed, 6 Apr 2022 10:13:11 +0200 From: David Disseldorp To: "NeilBrown" Cc: "Al Viro" , linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, "LKML" , "Jeff Layton" Subject: Re: [PATCH v4] VFS: filename_create(): fix incorrect intent. Message-ID: <20220406101311.502aa172@suse.de> In-Reply-To: <164878611050.25542.6758961460499392000@noble.neil.brown.name> References: <164877264126.25542.1271530843099472952@noble.neil.brown.name> <164878611050.25542.6758961460499392000@noble.neil.brown.name> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, 01 Apr 2022 15:08:30 +1100, NeilBrown wrote: > When asked to create a path ending '/', but which is not to be a > directory (LOOKUP_DIRECTORY not set), filename_create() will never try > to create the file. If it doesn't exist, -ENOENT is reported. > > However, it still passes LOOKUP_CREATE|LOOKUP_EXCL to the filesystems > ->lookup() function, even though there is no intent to create. This is > misleading and can cause incorrect behaviour. > > If you try > ln -s foo /path/dir/ It'd be helpful if we could run these sorts of tests from the xfstests suite. I wonder whether some sort of other-client ssh backchannel would be useful (for cifs.ko and cephfs too). > where 'dir' is a directory on an NFS filesystem which is not currently > known in the dcache, this will fail with ENOENT. > As the name is not in the dcache, nfs_lookup gets called with > LOOKUP_CREATE|LOOKUP_EXCL and so it returns NULL without performing any > lookup, with the expectation that a subsequent call to create the > target will be made, and the lookup can be combined with the creation. > In the case with a trailing '/' and no LOOKUP_DIRECTORY, that call is never > made. Instead filename_create() sees that the dentry is not (yet) > positive and returns -ENOENT - even though the directory actually > exists. > > So only set LOOKUP_CREATE|LOOKUP_EXCL if there really is an intent > to create, and use the absence of these flags to decide if -ENOENT > should be returned. > > Note that filename_parentat() is only interested in LOOKUP_REVAL, so we > split that out and store it in 'reval_flag'. > __looku_hash() then gets reval_flag combined with whatever create flags > were determined to be needed. nit: __lookup_hash() > > Signed-off-by: NeilBrown > --- > fs/namei.c | 22 ++++++++++------------ > 1 file changed, 10 insertions(+), 12 deletions(-) > > ARG - v3 had a missing semi-colon. Sorry. > > diff --git a/fs/namei.c b/fs/namei.c > index 3f1829b3ab5b..509657fdf4f5 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -3673,18 +3673,14 @@ static struct dentry *filename_create(int dfd, struct filename *name, > { > struct dentry *dentry = ERR_PTR(-EEXIST); > struct qstr last; > + bool want_dir = lookup_flags & LOOKUP_DIRECTORY; > + unsigned int reval_flag = lookup_flags & LOOKUP_REVAL; > + unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL; > int type; > int err2; > int error; > - bool is_dir = (lookup_flags & LOOKUP_DIRECTORY); > > - /* > - * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any > - * other flags passed in are ignored! > - */ > - lookup_flags &= LOOKUP_REVAL; > - > - error = filename_parentat(dfd, name, lookup_flags, path, &last, &type); > + error = filename_parentat(dfd, name, reval_flag, path, &last, &type); > if (error) > return ERR_PTR(error); > > @@ -3698,11 +3694,13 @@ static struct dentry *filename_create(int dfd, struct filename *name, > /* don't fail immediately if it's r/o, at least try to report other errors */ > err2 = mnt_want_write(path->mnt); > /* > - * Do the final lookup. > + * Do the final lookup. Suppress 'create' if there is a trailing > + * '/', and a directory wasn't requested. > */ > - lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL; > + if (last.name[last.len] && !want_dir) > + create_flags = 0; > inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); > - dentry = __lookup_hash(&last, path->dentry, lookup_flags); > + dentry = __lookup_hash(&last, path->dentry, reval_flag | create_flags); > if (IS_ERR(dentry)) > goto unlock; > > @@ -3716,7 +3714,7 @@ static struct dentry *filename_create(int dfd, struct filename *name, > * all is fine. Let's be bastards - you had / on the end, you've > * been asking for (non-existent) directory. -ENOENT for you. > */ > - if (unlikely(!is_dir && last.name[last.len])) { > + if (unlikely(!create_flags)) { > error = -ENOENT; > goto fail; > } Looks good and works for me. Reviewed-by: David Disseldorp