From patchwork Mon Jun 1 20:08:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 1301922 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=kernel.org Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=default header.b=bWKFmytT; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 49bR7m6bFqz9sWY for ; Tue, 2 Jun 2020 06:08:36 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728350AbgFAUIf (ORCPT ); Mon, 1 Jun 2020 16:08:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:46552 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726201AbgFAUIf (ORCPT ); Mon, 1 Jun 2020 16:08:35 -0400 Received: from sol.hsd1.ca.comcast.net (c-107-3-166-239.hsd1.ca.comcast.net [107.3.166.239]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D119E20734; Mon, 1 Jun 2020 20:08:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591042115; bh=85zG2AyYa1iBuFIil+uEjS+WxblsLLJ2fCz4UIcuvB0=; h=From:To:Cc:Subject:Date:From; b=bWKFmytTENc3vIROh8oQVWS1O0w1comVKM+t+gE9ks8imExM5DT6P5bLl2uv+8F+H kmKMJK+ltnLXxYGFjA24VPmHpyD6aZeUlxiqtthaluyVGj9zT+YnYHpP8gR62W6Q4a t3oNWPVc1HbbNM3uvgCrfqsnhMQ48ZHYrh1mJSXE= From: Eric Biggers To: linux-f2fs-devel@lists.sourceforge.net Cc: linux-ext4@vger.kernel.org, Daniel Rosenberg , stable@vger.kernel.org, Al Viro , linux-fsdevel@vger.kernel.org, Gabriel Krisman Bertazi Subject: [PATCH v2] f2fs: avoid utf8_strncasecmp() with unstable name Date: Mon, 1 Jun 2020 13:08:05 -0700 Message-Id: <20200601200805.59655-1-ebiggers@kernel.org> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org 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 Reviewed-by: Chao Yu --- v2: Use memcpy() + barrier() instead of a byte-by-byte copy. Also rebased onto f2fs/dev. fs/f2fs/dir.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index 29f70f2295cce..d35976785e8c5 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -1114,11 +1114,27 @@ static int f2fs_d_compare(const struct dentry *dentry, unsigned int len, const struct inode *dir = READ_ONCE(parent->d_inode); const struct f2fs_sb_info *sbi = F2FS_SB(dentry->d_sb); struct qstr entry = QSTR_INIT(str, len); + char strbuf[DNAME_INLINE_LEN]; int res; if (!dir || !IS_CASEFOLDED(dir)) goto fallback; + /* + * 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) { + memcpy(strbuf, str, len); + strbuf[len] = 0; + entry.name = strbuf; + /* prevent compiler from optimizing out the temporary buffer */ + barrier(); + } + res = utf8_strncasecmp(sbi->s_encoding, name, &entry); if (res >= 0) return res;