From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 277C2140381; Wed, 17 Apr 2024 13:30:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713360607; cv=none; b=UAapLek0ysUvc4urlruDuIP+M8bVgVem9WOiAOB9FTt0E8W2reveBOc2v+ZoFN55btVN8YZmHjYR2wumXMoOa07vsasdmS8pshkjGBmEwN18+o6G3IdKNoYori2WQRXRhbPx4ra0xoLnvvRKJ+kKwY4y6izeOrMvqolRWhu9mac= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713360607; c=relaxed/simple; bh=GyHbhmJ+9xPNnXgNXVIFixxq2fw78zbU6823wMnDiuw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GQ0kyVzdwWI/QWq1ydR7wd6EVKo98Wzta6ISnRBoC5R3RbqE6zLjoyvFH83cs1blaapffPR1SCjKEgHtD1uIAsu8wfNkg24Vl+gtcRN0+6MddfIc0fE12SvO4WWLfqgU1UBbMX8bhL3klQAzP7bfNCxGYJUBkY5OiXnGwdqJ/Kk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=S+2TnFv4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="S+2TnFv4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88FABC072AA; Wed, 17 Apr 2024 13:30:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1713360606; bh=GyHbhmJ+9xPNnXgNXVIFixxq2fw78zbU6823wMnDiuw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=S+2TnFv4zen3mDTIhf+eb4GHfX2E0l85VNscHmwnOqsEWCHDzjxB5yuUrFjArq9V3 dFu60UNJL/uXIO2Nff4vEmJBJ3022OHGn6kxVEQG4JNH64PGZONcfxb8ObHx9KbxZO X6aIO7dNJUszGvkt1u/v4oUnNcdlFYA+P7myXtWA= Date: Wed, 17 Apr 2024 15:30:03 +0200 From: Greg Kroah-Hartman To: Jan Kara Cc: cve@kernel.org, linux-kernel@vger.kernel.org, linux-cve-announce@vger.kernel.org Subject: Re: CVE-2024-26774: ext4: avoid dividing by 0 in mb_update_avg_fragment_size() when block bitmap corrupt Message-ID: <2024041711-chapter-uninstall-b1d3@gregkh> References: <2024040308-CVE-2024-26774-52d9@gregkh> <20240417114324.c77wuw5hvjbm6ok5@quack3> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240417114324.c77wuw5hvjbm6ok5@quack3> On Wed, Apr 17, 2024 at 01:43:24PM +0200, Jan Kara wrote: > Hello! > > On Wed 03-04-24 19:31:41, Greg Kroah-Hartman wrote: > > Description > > =========== > > > > In the Linux kernel, the following vulnerability has been resolved: > > > > ext4: avoid dividing by 0 in mb_update_avg_fragment_size() when block bitmap corrupt > > > > Determine if bb_fragments is 0 instead of determining bb_free to eliminate > > the risk of dividing by zero when the block bitmap is corrupted. > > > > The Linux kernel CVE team has assigned CVE-2024-26774 to this issue. > > I'd like to understand what is the imagined security threat fixed by this > patch (as multiple patches of similar nature got assigned a CVE). The patch > fixes a bug that if a corrupted filesystem is read-write mounted, we can do > division-by-zero. Now if you can make the system mount a corrupted > filesystem, you can do many interesting things to the system other than > create a division by zero... So what is the presumed threat model here? Exactly what you said, "if you mount a corrupted file system, you will get a divide by zero fault." Many systems auto-mount any filesystem plugged into it. If yours do not, then yours does not need to worry about this type of CVE. thanks, greg k-h