Messages in this thread | | | Date | Wed, 17 Apr 2024 18:12:04 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: CVE-2024-26774: ext4: avoid dividing by 0 in mb_update_avg_fragment_size() when block bitmap corrupt |
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On Wed, Apr 17, 2024 at 04:54:46PM +0200, Jan Kara wrote: > On Wed 17-04-24 15:30:03, Greg Kroah-Hartman wrote: > > 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. > > OK, understood. But let me state that with the current state of affairs in > the filesystem land, it will not take a determined attacker long to get > arbitrary code execution out of "maliciously corrupted fs mounted". The > code of most filesystems has simply never been written with the assumption > that it can be presented with malicious data and we have hundreds of > thousands lines of code like that. We have fixed the most glaring problems > but by far not all (partly because of performance and maintenance costs, > partly because they are baked into on-disk formats).
I totally agree. It's up to the distros to stop doing this if they wish to stop this problem from happening.
thanks,
greg k-h
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