kernel BUG at mm/usercopy.c:72!

[Michael Ellerman]

Kees Cook <keescook at chromium.org> writes:
> On Tue, May 16, 2017 at 4:09 AM, Michael Ellerman <mpe at ellerman.id.au> wrote:
>> Yeah it looks like powerpc also suffers from the same bug that arm64
>> used to, ie. virt_addr_valid() will return true for some vmalloc
>> addresses.
>>
>> virt_addr_valid() is used pretty widely, I'm not sure if we can just fix
>> it without other fallout. I'll dig a bit more tomorrow if no one beats
>> me to it.
>>
>> Kees, depending on how that turns out we may ask you to revert
>> 517e1fbeb65f ("mm/usercopy: Drop extra is_vmalloc_or_module() check").
>
> That's fine by me. Let me know what you think would be best.

Oh man, what a mess.

I think we can do a small fix for this in powerpc code for 4.12, will
post it soon for Breno to test - I still can't reproduce locally.

cheers