Re: [PATCH v2] KEYS: prevent NULL pointer dereference in find_asymmetric_key()

Jarkko Sakkinen
2024-09-11T13:18:07Z

On Tue Sep 10, 2024 at 8:38 PM EEST, Sergey Shtylyov wrote:
> On 9/10/24 4:38 PM, Jarkko Sakkinen wrote:
> [...]
>
> >> In find_asymmetric_key(), if all NULLs are passed in id_{0,1,2} parameters
> >> the kernel will first emit WARN and then have an oops because id_2 gets
> >> dereferenced anyway.
> >>
> >> Found by Linux Verification Center (linuxtesting.org) with Svace static
> >> analysis tool.
> >
> > Weird, I recall that I've either sent a patch to address the same site
> > OR have commented a patch with similar reasoning. Well, it does not
> > matter, I think it this makes sense to me.
> >
> > You could further add to the motivation that given the panic_on_warn
> > kernel command-line parameter, it is for the best limit the scope and
> > use of the WARN-macro.
>
> I don't understand what you mean -- this version of the patch keeps
> the WARN_ON() call, it just moves that call, so that the duplicate id_{0,1,2}
> checks are avoided...

I overlooked the code change (my bad sorry). Here's a better version of
the first paragraph:

"find_asymmetric_keys() has nullity checks of id_0 and id_1 but ignores
validation for id_2. Check nullity also for id_2."

Yep, and it changes no situation with WARN_ON() macro for better or
worse. It would logically separate issue to discuss and address so
as far as I'm concerned, with this clarification I think the change
makes sense to me.

BR, Jarkko