From patchwork Thu May 20 09:23:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 443995 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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_RED, USER_AGENT_GIT 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 B61B5C41602 for ; Thu, 20 May 2021 11:24:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A77866141A for ; Thu, 20 May 2021 11:24:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241883AbhETLZm (ORCPT ); Thu, 20 May 2021 07:25:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:41684 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236564AbhETLWM (ORCPT ); Thu, 20 May 2021 07:22:12 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4933A6105A; Thu, 20 May 2021 10:11:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1621505500; bh=qgA/fXD4F6Koj9VdCi58OxcitLjK1laDKud+WmMKar8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OociV8P/4izf7tM6f7GDUe15yuW3NBvCUqsTQK/qI9XeZEnqgyAzsklFxcZ4HRpzh HbTQwwJD4GihZ4VBCqxcFSwRWBVCFiUVjGBZQQIiJeGDB3b5SLsKmv0otyGomtWWWZ YDlgRQqnrhVvOUtBBoosyL2SlmkmzJJd+lX1Z6iI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Phillip Lougher , syzbot+e8f781243ce16ac2f962@syzkaller.appspotmail.com, syzbot+7b98870d4fec9447b951@syzkaller.appspotmail.com, Andrew Morton , Linus Torvalds Subject: [PATCH 4.4 164/190] squashfs: fix divide error in calculate_skip() Date: Thu, 20 May 2021 11:23:48 +0200 Message-Id: <20210520092107.590542533@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210520092102.149300807@linuxfoundation.org> References: <20210520092102.149300807@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Phillip Lougher commit d6e621de1fceb3b098ebf435ef7ea91ec4838a1a upstream. Sysbot has reported a "divide error" which has been identified as being caused by a corrupted file_size value within the file inode. This value has been corrupted to a much larger value than expected. Calculate_skip() is passed i_size_read(inode) >> msblk->block_log. Due to the file_size value corruption this overflows the int argument/variable in that function, leading to the divide error. This patch changes the function to use u64. This will accommodate any unexpectedly large values due to corruption. The value returned from calculate_skip() is clamped to be never more than SQUASHFS_CACHED_BLKS - 1, or 7. So file_size corruption does not lead to an unexpectedly large return result here. Link: https://lkml.kernel.org/r/20210507152618.9447-1-phillip@squashfs.org.uk Signed-off-by: Phillip Lougher Reported-by: Reported-by: Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/squashfs/file.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/fs/squashfs/file.c +++ b/fs/squashfs/file.c @@ -224,11 +224,11 @@ failure: * If the skip factor is limited in this way then the file will use multiple * slots. */ -static inline int calculate_skip(int blocks) +static inline int calculate_skip(u64 blocks) { - int skip = blocks / ((SQUASHFS_META_ENTRIES + 1) + u64 skip = blocks / ((SQUASHFS_META_ENTRIES + 1) * SQUASHFS_META_INDEXES); - return min(SQUASHFS_CACHED_BLKS - 1, skip + 1); + return min((u64) SQUASHFS_CACHED_BLKS - 1, skip + 1); }