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=-6.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=unavailable 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 9C0CCC433E0 for ; Sat, 30 May 2020 06:17:24 +0000 (UTC) Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 646EF2073B; Sat, 30 May 2020 06:17:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sourceforge.net header.i=@sourceforge.net header.b="MxntQj7z"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sf.net header.i=@sf.net header.b="D9GVNv/p" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 646EF2073B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=collabora.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-f2fs-devel-bounces@lists.sourceforge.net Received: from [127.0.0.1] (helo=sfs-ml-1.v29.lw.sourceforge.com) by sfs-ml-1.v29.lw.sourceforge.com with esmtp (Exim 4.90_1) (envelope-from ) id 1jeuo7-00053P-UW; Sat, 30 May 2020 06:17:23 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-1.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jeuo6-00053A-9a for linux-f2fs-devel@lists.sourceforge.net; Sat, 30 May 2020 06:17:22 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Type:MIME-Version:Message-ID:In-Reply-To: Date:References:Subject:Cc:To:From:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=J0glF3H5946zPDWdiae7Gp/+QSDi4Qdumm0IQgdOR58=; b=MxntQj7zLQ+fh8CH7pH0DxvdDv n6YsbLkuHuILF7G0K/erfrEp1+wr9S5Ao7+odsG2Sp+ahdDaUCPNrOX5CjyycfFExwaGFaHnU4Bfa USjaS1v3R4uLK+x4A96amsYLupx7qzzJ6MzDPRgGpTNJbAu/ePs94t4JLQ5wvKh5rhRw=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Content-Type:MIME-Version:Message-ID:In-Reply-To:Date:References:Subject: Cc:To:From:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=J0glF3H5946zPDWdiae7Gp/+QSDi4Qdumm0IQgdOR58=; b=D9GVNv/piUOB8Fy/GEc+RSuzyx IGPiTSLeIHXEK5FjoHys9ERtXpasNhjQts23hqtE0j8EF+XNqzwkv3xapehbRWNOmyP0vTw1x/xpJ TbKzRq9MB7M1tw1teEN4AIEPUCT39ByofpDim+XZJZ1IvuFX6PKnvJutG4Wf5jwRZvG0=; Received: from bhuna.collabora.co.uk ([46.235.227.227]) by sfi-mx-4.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.2) id 1jeuo4-003eAi-9C for linux-f2fs-devel@lists.sourceforge.net; Sat, 30 May 2020 06:17:22 +0000 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: krisman) with ESMTPSA id 121BA2A49A0 From: Gabriel Krisman Bertazi To: Eric Biggers Organization: Collabora References: <20200530060216.221456-1-ebiggers@kernel.org> Date: Sat, 30 May 2020 02:17:02 -0400 In-Reply-To: <20200530060216.221456-1-ebiggers@kernel.org> (Eric Biggers's message of "Fri, 29 May 2020 23:02:16 -0700") Message-ID: <85d06mkkv5.fsf@collabora.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Headers-End: 1jeuo4-003eAi-9C Subject: Re: [f2fs-dev] [PATCH] ext4: avoid utf8_strncasecmp() with unstable name X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Daniel Rosenberg , stable@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Al Viro , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Gabriel Krisman Bertazi Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net Eric Biggers writes: > 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: b886ee3e778e ("ext4: Support case-insensitive file name lookups") > Cc: # v5.2+ > Cc: Al Viro > Cc: Daniel Rosenberg > Cc: Gabriel Krisman Bertazi > Signed-off-by: Eric Biggers > --- > fs/ext4/dir.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c > index c654205f648dd..19aef8328bb18 100644 > --- a/fs/ext4/dir.c > +++ b/fs/ext4/dir.c > @@ -675,6 +675,7 @@ static int ext4_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) || > !EXT4_SB(inode->i_sb)->s_encoding) { > @@ -683,6 +684,22 @@ static int ext4_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; > + } > + Could we avoid this if the casefolded version were cached in the dentry? Then we could use utf8_strncasecmp_folded which would be safe. Would this be acceptable for vfs? > return ext4_ci_compare(inode, name, &qstr, false); > } -- Gabriel Krisman Bertazi _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel