Re: CVE-2016-5011: util-linux: Extended partition loop in MBR partition table leads to DoS

[Cedric Buissart <cbuissar () redhat com>]

On Mon, Jul 11, 2016 at 5:19 PM, Florian Weimer <fweimer () redhat com> wrote:

> On 07/11/2016 01:32 PM, Cedric Buissart wrote:
>
> I looked at other projects to see what is being done to prevent this
> > particular loop from happening. Until now, tools I checked are protected
> > either by detecting the loop (i.e.: actively searching for a relative
> > offset of 0 for the next EBR, as done by this util-linux patch; partprobe
> > and fdisk are doing that), or enforcing a limit on the maximum number of
> > partitions for a device (Linux kernel, kpartx & other tools I currently
> > checked)
>
> How does util-linux protect against loops which are non-empty?  Does it
> reject negative offsets?
Indeed, the the patch wasn't sufficient.
The following has been added, in order to prevent jumping back to a
precedent EBR :
https://github.com/karelzak/util-linux/commit/50d1594c2e6142a3b51d2143c74027480df082e0


> Thanks,
> Florian



-- 
Cedric Buissart,
Product Security