From nobody Wed Sep 17 06:23:23 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48EF5C4332F for ; Thu, 22 Dec 2022 02:02:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234562AbiLVCCn (ORCPT ); Wed, 21 Dec 2022 21:02:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229620AbiLVCCj (ORCPT ); Wed, 21 Dec 2022 21:02:39 -0500 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E139220F6D for ; Wed, 21 Dec 2022 18:02:38 -0800 (PST) Received: by mail-pl1-x632.google.com with SMTP id jn22so628756plb.13 for ; Wed, 21 Dec 2022 18:02:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=content-transfer-encoding:mime-version:message-id:date:subject:to :from:from:to:cc:subject:date:message-id:reply-to; bh=/vSB+l3+h0STRS9DPPu2XELvIiGiSoWBn/FlK1C83SA=; b=ou9acgIDlwQ3xDhECuqvM25H6FtaND3bPaqdjPAqWdAhqo7Y83YVVOiGn0oWKpRBS4 vdgdqILkVAYHVfYdf3pof6pdXyJCljnEs1wptCI9ej7Cr5ZAZl7t3PNkhtzsg1W3bURS 2HV6er5F+bAYJRN1hxlb+2zSVOYMkz7cfO219sfs7x/Gq2WOpVPAOuneveYdLQEqPNo2 /u7t31kWI4LUDAVT50QZFdyQZlAbgClBC1npmARQJs8QRnxoa/Y+JaRC1ofFSMs1nIk8 eSyFzxaLsJjIdkigx9S0+zBa5ISSuOse5qFZ5m7kcu4uxDC5ykAF2+Vzkbq69ZX0hlll tKow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:to :from:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=/vSB+l3+h0STRS9DPPu2XELvIiGiSoWBn/FlK1C83SA=; b=0uU9PXaqoLdzY760wOb7vl4L/uonGBQuRkw4FP+3qAO0BHzyAxOAcnZ/2y0euMuxO/ 8JkODUgxdNTmBMs1691jmqcmnpwW0r6CX+gkzVXMKqWFLmDYPWnlqm0VTFl0wIqKiMxW fI7UwBIZxZbpXHv0ZHenLYLfrdGLXoGkPu2iUuL2Pv6urfZs+uJ4mc3mtHlQaiMNqeSi 1i3Mjax4BKY9yLRXYt6FcEp7spEPBcciNbLs0Z9iu11Qu628yaXopsNhPgTeqLMnJKCv LrMzGDSJnf+ca+7jFsEoMKdA+1ZxVALZWAFKXgKnHDoqzAPAlvAyg4a8axwlmaFndWIw yS4A== X-Gm-Message-State: AFqh2kqXqck/JVL3shc7HyR6G5A+f6WMXTgQo+1EfFNHHeROZWXxFjCa 7500VqTAhvJOMxFCcRqHFmpywg== X-Google-Smtp-Source: AMrXdXvj/o3WHvnJUk8+g2IpdvN05DyQP5K+Yj2TLou5ynvcpC3HezzZFC19XqQqVNUb6wvxw/khvQ== X-Received: by 2002:a17:902:82c8:b0:191:4389:f8fb with SMTP id u8-20020a17090282c800b001914389f8fbmr3938992plz.65.1671674558276; Wed, 21 Dec 2022 18:02:38 -0800 (PST) Received: from niej-dt-7B47.. (80.251.214.228.16clouds.com. [80.251.214.228]) by smtp.gmail.com with ESMTPSA id k15-20020a170902c40f00b001869b988d93sm12154909plk.187.2022.12.21.18.02.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Dec 2022 18:02:37 -0800 (PST) From: Jun Nie To: tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] ext4: fix underflow in group bitmap calculation Date: Thu, 22 Dec 2022 10:02:44 +0800 Message-Id: <20221222020244.1821308-1-jun.nie@linaro.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" There is case that s_first_data_block is not 0 and block nr is smaller than s_first_data_block when calculating group bitmap during allocation. This underflow make index exceed es->s_groups_count in ext4_get_group_info() and trigger the BUG_ON. Fix it with protection of underflow. Fixes: 72b64b594081ef ("ext4 uninline ext4_get_group_no_and_offset()") Link: https://syzkaller.appspot.com/bug?id=3D79d5768e9bfe362911ac1a5057a36f= c6b5c30002 Reported-by: syzbot+6be2b977c89f79b6b153@syzkaller.appspotmail.com Signed-off-by: Jun Nie --- fs/ext4/balloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 8ff4b9192a9f..177ef6bd635a 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -56,7 +56,8 @@ void ext4_get_group_no_and_offset(struct super_block *sb,= ext4_fsblk_t blocknr, struct ext4_super_block *es =3D EXT4_SB(sb)->s_es; ext4_grpblk_t offset; =20 - blocknr =3D blocknr - le32_to_cpu(es->s_first_data_block); + blocknr =3D blocknr > le32_to_cpu(es->s_first_data_block) ? + blocknr - le32_to_cpu(es->s_first_data_block) : 0; offset =3D do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb)) >> EXT4_SB(sb)->s_cluster_bits; if (offsetp) --=20 2.34.1