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=-20.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 16261C07E9B for ; Mon, 19 Jul 2021 17:12:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E553460FEA for ; Mon, 19 Jul 2021 17:12:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346596AbhGSQb5 (ORCPT ); Mon, 19 Jul 2021 12:31:57 -0400 Received: from mail.kernel.org ([198.145.29.99]:57556 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345705AbhGSPQs (ORCPT ); Mon, 19 Jul 2021 11:16:48 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id C7ECA60FDA; Mon, 19 Jul 2021 15:57:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626710221; bh=+uFTDpvKhWHlQ5H7ysMc7Ohh59fU2zT9cKN7k1vT62k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FIWz1ZoOqnM96yRRTBhvTDd/6a0j05IOv2ISY/gDOC5K/1ztqWYDVoZwcORgFRel6 D0LVdbP9u6L2AGuABz1AIVjfTepRfGeYjHbhlzfg9ld6WZeGRd9xXaQD/8qYZf6FBX Lri8e1XuUiIze2HVLuvbNYXMSKpJOKFS7kAkHW+g= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dimitri John Ledkov , Kyungsik Lee , Yinghai Lu , Bongkyu Kim , Kees Cook , Sven Schmidt <4sschmid@informatik.uni-hamburg.de>, Rajat Asthana , Nick Terrell , Gao Xiang , Andrew Morton , Linus Torvalds , Sasha Levin Subject: [PATCH 5.10 109/243] lib/decompress_unlz4.c: correctly handle zero-padding around initrds. Date: Mon, 19 Jul 2021 16:52:18 +0200 Message-Id: <20210719144944.420276893@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210719144940.904087935@linuxfoundation.org> References: <20210719144940.904087935@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dimitri John Ledkov [ Upstream commit 2c484419efc09e7234c667aa72698cb79ba8d8ed ] lz4 compatible decompressor is simple. The format is underspecified and relies on EOF notification to determine when to stop. Initramfs buffer format[1] explicitly states that it can have arbitrary number of zero padding. Thus when operating without a fill function, be extra careful to ensure that sizes less than 4, or apperantly empty chunksizes are treated as EOF. To test this I have created two cpio initrds, first a normal one, main.cpio. And second one with just a single /test-file with content "second" second.cpio. Then i compressed both of them with gzip, and with lz4 -l. Then I created a padding of 4 bytes (dd if=/dev/zero of=pad4 bs=1 count=4). To create four testcase initrds: 1) main.cpio.gzip + extra.cpio.gzip = pad0.gzip 2) main.cpio.lz4 + extra.cpio.lz4 = pad0.lz4 3) main.cpio.gzip + pad4 + extra.cpio.gzip = pad4.gzip 4) main.cpio.lz4 + pad4 + extra.cpio.lz4 = pad4.lz4 The pad4 test-cases replicate the initrd load by grub, as it pads and aligns every initrd it loads. All of the above boot, however /test-file was not accessible in the initrd for the testcase #4, as decoding in lz4 decompressor failed. Also an error message printed which usually is harmless. Whith a patched kernel, all of the above testcases now pass, and /test-file is accessible. This fixes lz4 initrd decompress warning on every boot with grub. And more importantly this fixes inability to load multiple lz4 compressed initrds with grub. This patch has been shipping in Ubuntu kernels since January 2021. [1] ./Documentation/driver-api/early-userspace/buffer-format.rst BugLink: https://bugs.launchpad.net/bugs/1835660 Link: https://lore.kernel.org/lkml/20210114200256.196589-1-xnox@ubuntu.com/ # v0 Link: https://lkml.kernel.org/r/20210513104831.432975-1-dimitri.ledkov@canonical.com Signed-off-by: Dimitri John Ledkov Cc: Kyungsik Lee Cc: Yinghai Lu Cc: Bongkyu Kim Cc: Kees Cook Cc: Sven Schmidt <4sschmid@informatik.uni-hamburg.de> Cc: Rajat Asthana Cc: Nick Terrell Cc: Gao Xiang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- lib/decompress_unlz4.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/lib/decompress_unlz4.c b/lib/decompress_unlz4.c index c0cfcfd486be..e6327391b6b6 100644 --- a/lib/decompress_unlz4.c +++ b/lib/decompress_unlz4.c @@ -112,6 +112,9 @@ STATIC inline int INIT unlz4(u8 *input, long in_len, error("data corrupted"); goto exit_2; } + } else if (size < 4) { + /* empty or end-of-file */ + goto exit_3; } chunksize = get_unaligned_le32(inp); @@ -125,6 +128,10 @@ STATIC inline int INIT unlz4(u8 *input, long in_len, continue; } + if (!fill && chunksize == 0) { + /* empty or end-of-file */ + goto exit_3; + } if (posp) *posp += 4; @@ -184,6 +191,7 @@ STATIC inline int INIT unlz4(u8 *input, long in_len, } } +exit_3: ret = 0; exit_2: if (!input) -- 2.30.2