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SubjectRe: [PATCH] ubi: avoid workqueue format string leak
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On Tue, 2014-04-08 at 10:57 -0300, Ezequiel Garcia wrote:
> Hello Kees,
>
> Thanks for the patch.
>
> On Apr 07, Kees Cook wrote:
> > When building the name for the workqueue thread, make sure a format
> > string cannot leak in from the disk name.
> >
>
> Could you enlighten me and explain why you want to avoid the name leak?
> Is it a security concern?
>
> I'd like to understad this better, so I can avoid making such mistakes
> in the future.

Well, the basics seem to be simple, attacker makes sure gd->disk_name
contains a bunch of "%s" and other placeholders, and this leads
"workqueue_alloc()" to read kernel memory and form the workqueue name.

I did not think it through further, though, but that was enough for me
to apply the patch right away. But yeah, curios parts are:

1. How attacker could end up with a crafted "gd->disk_name"
2. How attacker gets the workqueue name then, I guess there is a sysfs
file or something, but I do not know off the top of my head.

Yeah, I am interested to get educated on this a too.

--
Best Regards,
Artem Bityutskiy



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