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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 D5096C07E9B for ; Sat, 10 Jul 2021 02:42:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BE2F3613C5 for ; Sat, 10 Jul 2021 02:42:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235428AbhGJCpZ (ORCPT ); Fri, 9 Jul 2021 22:45:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:34536 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235412AbhGJCns (ORCPT ); Fri, 9 Jul 2021 22:43:48 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2E35B6141A; Sat, 10 Jul 2021 02:39:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625884787; bh=YXEHPD2Vi2xEUHW1TMUFHUcpQOipBhA/X0A+7MOjTEs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NcnECSuOF+V2XKHUHDm4OPbdRazcOonnmgmdd8kgzwZSPoGMbW5ldXOf1UXbqGNFP 1Y6pW6aMjS8Gf1CpcqYhBe/kGQn2RAZ9kYBR8tYG4JaUHLUallRzpc8M527a55dfgu PhASfemjL5eiyemhG6ToUilc7Cqt3v2cAVtlyPkSEQ5Px2gB+Q6+DZ8vrwlWB2QWHj iXq6eT4P8C3+MFBPLBZVM8n7BVqUXnvUqgAufNBJIhmqdUfUnrDJAqs9/ELalOIe4A 9seQSo78jaHfBhHxzy2B96HHATIKR8VEr/6NCQesBw6aUWHgY/DvJezg1Omb3ltadr qu9L2ZL2ylojg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: 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 AUTOSEL 4.4 23/23] lib/decompress_unlz4.c: correctly handle zero-padding around initrds. Date: Fri, 9 Jul 2021 22:39:12 -0400 Message-Id: <20210710023912.3172972-23-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210710023912.3172972-1-sashal@kernel.org> References: <20210710023912.3172972-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 036fc882cd72..f1449244fdd4 100644 --- a/lib/decompress_unlz4.c +++ b/lib/decompress_unlz4.c @@ -115,6 +115,9 @@ 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); @@ -128,6 +131,10 @@ 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