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 4E62EC76196 for ; Fri, 31 Mar 2023 15:31:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232890AbjCaPbT (ORCPT ); Fri, 31 Mar 2023 11:31:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53754 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231247AbjCaPbS (ORCPT ); Fri, 31 Mar 2023 11:31:18 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A60EB1D2E7; Fri, 31 Mar 2023 08:31:17 -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-out1.suse.de (Postfix) with ESMTPS id 5D86C219C6; Fri, 31 Mar 2023 15:31:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1680276676; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Mjlb0/eHfvgS2ZXDdMn4kdD62mILFu+OjmdPhxiyTJU=; b=RRIGNMGk6XvNTiArrMsl+QcESXBJGs9NjtsuoiZC2LuAzOVV+RQqa5rh5aA2pqiT9wuhHO /eKtlv46Iov/okzaFBNkqjlowo5qfqoDb9FZno0NVJvTNrYSSSLZ1loy7H463xuedzRcya 7/VqOltMaqAYn2YSeO3ic/w2iYOmYhs= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1680276676; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Mjlb0/eHfvgS2ZXDdMn4kdD62mILFu+OjmdPhxiyTJU=; b=AYJWCk4OYFBa7u8prX6m7h4FVCbcEypLc/iV6GW7AjiptLQSdX4is1shSP8Hshubtx8riE 0Sfpm5wwLn8grHCw== 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 CBC8B133B6; Fri, 31 Mar 2023 15:31:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 4LwCJMP8JmQMDAAAMHmgww (envelope-from ); Fri, 31 Mar 2023 15:31:15 +0000 From: Gabriel Krisman Bertazi To: Al Viro Cc: kernel@collabora.com, tytso@mit.edu, linux-f2fs-devel@lists.sourceforge.net, ebiggers@kernel.org, linux-fsdevel@vger.kernel.org, jaegeuk@kernel.org, linux-ext4@vger.kernel.org Subject: Re: [f2fs-dev] [PATCH 3/7] libfs: Validate negative dentries in case-insensitive directories References: <20220622194603.102655-1-krisman@collabora.com> <20220622194603.102655-4-krisman@collabora.com> <20230326044627.GD3390869@ZenIV> Date: Fri, 31 Mar 2023 12:31:13 -0300 In-Reply-To: <20230326044627.GD3390869@ZenIV> (Al Viro's message of "Sun, 26 Mar 2023 05:46:27 +0100") Message-ID: <874jq10wfy.fsf@suse.de> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Al Viro writes: > On Wed, Jun 22, 2022 at 03:45:59PM -0400, Gabriel Krisman Bertazi wrote: > >> +static inline int generic_ci_d_revalidate(struct dentry *dentry, >> + const struct qstr *name, >> + unsigned int flags) >> +{ >> + int is_creation = flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET); >> + >> + if (d_is_negative(dentry)) { >> + const struct dentry *parent = READ_ONCE(dentry->d_parent); >> + const struct inode *dir = READ_ONCE(parent->d_inode); >> + >> + if (dir && needs_casefold(dir)) { >> + if (!d_is_casefold_lookup(dentry)) >> + return 0; > > In which conditions does that happen? Hi Al, This can happen right after a case-sensitive directory is converted to case-insensitive. A previous case-sensitive lookup could have left a negative dentry in the dcache that we need to reject, because it doesn't have the same assurance of absence of all-variation of names as a negative dentry created during a case-insensitive lookup. >> + if (is_creation && >> + (dentry->d_name.len != name->len || >> + memcmp(dentry->d_name.name, name->name, name->len))) >> + return 0; >> + } >> + } >> + return 1; >> +} > > Analysis of stability of ->d_name, please. It's *probably* safe, but > the details are subtle and IMO should be accompanied by several asserts. > E.g. "we never get LOOKUP_CREATE in op->intent without O_CREAT in op->open_flag > for such and such reasons, and we verify that in such and such place"... > > A part of that would be "the call in lookup_dcache() can only get there > with non-zero flags when coming from __lookup_hash(), and that has parent locked, > stabilizing the name; the same goes for the call in __lookup_slow(), with the > only call chain with possibly non-zero flags is through lookup_slow(), where we > have the parent locked". However, lookup_fast() and lookup_open() have the > flags come from nd->flags, and LOOKUP_CREATE can be found there in several areas. > I _think_ we are guaranteed the parent locked in all such call chains, but that > is definitely worth at least a comment. Thanks for the example of the analysis what you are looking for here. That will help me quite a bit. I wrote this code a while ago and I don't recall the exact details. I will go through the code again and send a new version with the detailed analysis. -- Gabriel Krisman Bertazi