Re: Out-of-bounds access in get_wchan (arch/x86/kernel/process_64.c)

[Wolfram Gloger]

Kees Cook <kees@xxxxxxxxxxx> writes:

> Please note that these bounds checks aren't correct to begin with. Since
> a pointer is being dereferenced, the end boundry must be reduced by
> sizeof(unsigned long) as well.
>
> It looks like process_32.c suffers the same problems, too.

I can't see the end boundary problem in process_32.c.  The end checks
are properly reduced with the top_esp and top_ebp macros.

All I can see in process_32.c is that the check

		if (bp < stack_page || bp > top_ebp+stack_page)

could be replaced by:

		if (bp < stack_page-sizeof(unsigned long) || bp > top_ebp+stack_page)

but that is a relaxation and not an over/underrun fix.

Can you elaborate what problem you see in process_32.c?

Regards,
Wolfram.
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