From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Fri, 10 Apr 2026 13:52:10 +0200 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1wBAPC-00AdIx-2Q for lore@lore.pengutronix.de; Fri, 10 Apr 2026 13:52:10 +0200 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1wBAPC-00007S-60 for lore@pengutronix.de; Fri, 10 Apr 2026 13:52:10 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; 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Fri, 10 Apr 2026 13:51:36 +0200 Message-ID: <3666e81e-4969-495e-97e2-8c7cbcd1df9f@pengutronix.de> Date: Fri, 10 Apr 2026 13:51:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Sascha Hauer , BAREBOX Cc: "Claude Opus 4.6 (1M context)" References: <20260402-fs-ext4-buffer-overflows-v1-0-b9f8a909fe58@pengutronix.de> <20260402-fs-ext4-buffer-overflows-v1-2-b9f8a909fe58@pengutronix.de> From: Ahmad Fatoum Content-Language: en-US, de-DE, de-BE In-Reply-To: <20260402-fs-ext4-buffer-overflows-v1-2-b9f8a909fe58@pengutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260410_045139_702644_8F5BB7BA X-CRM114-Status: GOOD ( 15.66 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-5.2 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH 2/5] fs: ext4: reject superblocks with zero inodesz, gdsize or inodes_per_group X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) On 4/2/26 12:12 PM, Sascha Hauer wrote: > The superblock fields inode_size, descriptor_size, and inodes_per_group > are read from disk and used as divisors without validation: > > - inodesz == 0: division by zero in ext4fs_read_inode() > - gdsize == 0: division by zero in ext4fs_blockgroup() > - inodes_per_group == 0: division by zero in ext4fs_read_inode() > > All three are trivially triggered by a crafted filesystem image. > > Validate these fields are non-zero at mount time and reject the > filesystem if they aren't. > > Signed-off-by: Sascha Hauer > Co-Authored-By: Claude Opus 4.6 (1M context) Reviewed-by: Ahmad Fatoum > --- > fs/ext4/ext4_common.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c > index 094293a069..5d252b4a2c 100644 > --- a/fs/ext4/ext4_common.c > +++ b/fs/ext4/ext4_common.c > @@ -541,6 +541,15 @@ int ext4fs_mount(struct ext_filesystem *fs) > le32_to_cpu(data->sblock.revision_level), > fs->inodesz, fs->gdsize); > > + if (!fs->inodesz || !fs->gdsize || > + !le32_to_cpu(data->sblock.inodes_per_group)) { > + dev_err(fs->dev, "invalid superblock: inodesz=%u gdsize=%u inodes_per_group=%u\n", > + fs->inodesz, fs->gdsize, > + le32_to_cpu(data->sblock.inodes_per_group)); > + ret = -EINVAL; > + goto fail; > + } > + > data->diropen.data = data; > data->diropen.ino = 2; > data->diropen.inode_read = 1; > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |