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 X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43B5FC433E0 for ; Sat, 30 May 2020 15:07:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 10B192074D for ; Sat, 30 May 2020 15:07:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590851273; bh=VFC2e2QDPFdOJxydI3qWtpXTrKif7HwS+5L0IvnfvA0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=UAFtF1o22seC7OO49V1G3BfAz6nXcXrFBffIwhYcBXiSDffUWKv+34LT8HWAINe6Y sKDjHx3x/s8spp31ugGM5/+QRQLIfOgcMPI3Ggrz2DC98wnOt4h/PSTOucs+QcgPYC RaA2SIyvVDgP0M2KADb8XQ+Vrdqd9yiXtbzyK41I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729026AbgE3PHw (ORCPT ); Sat, 30 May 2020 11:07:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:51698 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728927AbgE3PHv (ORCPT ); Sat, 30 May 2020 11:07:51 -0400 Received: from localhost (unknown [104.132.1.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0848E20715; Sat, 30 May 2020 15:07:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590851271; bh=VFC2e2QDPFdOJxydI3qWtpXTrKif7HwS+5L0IvnfvA0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QU8rTwEO5UY8g832e8Juk2CySLLj8tTS0HmL+BgnaqGyakKYO97n+mG84Saq0PngC /WZEjiLYtZ1/USS/PLqjOliTkCoDlk+W0hOmpe28n4Lqhlz5N7ZhIfkOqWp0Z67lBF XwZdlN/y1PeZAE7UNpeDCouJg7qdIcMa8qkvHYTA= Date: Sat, 30 May 2020 08:07:50 -0700 From: Jaegeuk Kim To: Eric Biggers Cc: linux-f2fs-devel@lists.sourceforge.net, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org, Al Viro , Daniel Rosenberg , Gabriel Krisman Bertazi Subject: Re: [PATCH] f2fs: avoid utf8_strncasecmp() with unstable name Message-ID: <20200530150750.GA184700@google.com> References: <20200530060418.221707-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200530060418.221707-1-ebiggers@kernel.org> Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On 05/29, Eric Biggers wrote: > From: Eric Biggers > > If the dentry name passed to ->d_compare() fits in dentry::d_iname, then > it may be concurrently modified by a rename. This can cause undefined > behavior (possibly out-of-bounds memory accesses or crashes) in > utf8_strncasecmp(), since fs/unicode/ isn't written to handle strings > that may be concurrently modified. > > Fix this by first copying the filename to a stack buffer if needed. > This way we get a stable snapshot of the filename. > > Fixes: 2c2eb7a300cd ("f2fs: Support case-insensitive file name lookups") > Cc: # v5.4+ > Cc: Al Viro > Cc: Daniel Rosenberg > Cc: Gabriel Krisman Bertazi > Signed-off-by: Eric Biggers Acked-by: Jaegeuk Kim > --- > fs/f2fs/dir.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > index 44bfc464df787..5c179b72eb8a8 100644 > --- a/fs/f2fs/dir.c > +++ b/fs/f2fs/dir.c > @@ -1083,6 +1083,7 @@ static int f2fs_d_compare(const struct dentry *dentry, unsigned int len, > struct qstr qstr = {.name = str, .len = len }; > const struct dentry *parent = READ_ONCE(dentry->d_parent); > const struct inode *inode = READ_ONCE(parent->d_inode); > + char strbuf[DNAME_INLINE_LEN]; > > if (!inode || !IS_CASEFOLDED(inode)) { > if (len != name->len) > @@ -1090,6 +1091,22 @@ static int f2fs_d_compare(const struct dentry *dentry, unsigned int len, > return memcmp(str, name->name, len); > } > > + /* > + * If the dentry name is stored in-line, then it may be concurrently > + * modified by a rename. If this happens, the VFS will eventually retry > + * the lookup, so it doesn't matter what ->d_compare() returns. > + * However, it's unsafe to call utf8_strncasecmp() with an unstable > + * string. Therefore, we have to copy the name into a temporary buffer. > + */ > + if (len <= DNAME_INLINE_LEN - 1) { > + unsigned int i; > + > + for (i = 0; i < len; i++) > + strbuf[i] = READ_ONCE(str[i]); > + strbuf[len] = 0; > + qstr.name = strbuf; > + } > + > return f2fs_ci_compare(inode, name, &qstr, false); > } > > -- > 2.26.2