Re: [x86/uaccess] 5b710f34e1: kernel BUG at mm/usercopy.c:75!

[Kees Cook]

On Wed, Aug 17, 2016 at 2:55 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Aug 17, 2016 at 2:50 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>> On Wed, Aug 17, 2016 at 2:45 PM, Linus Torvalds
>>>
>>> Networking does, but seems to use __GFP_COMP, at least in the one case
>>> I checked (skbuff).
>>
>> Was this allocation really through kmalloc?
>
> The networking one I looked at, no. But they do __GFP_COMP.
>
> The task struct allocation generally is (alloc_task_struct_node()),
> but as Rik pointed out, SLOB doesn't actually necessarily do the slab
> book-keeping for multi-page allocations.

Perhaps I can just ifdef the multi-page checks with
CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR. That way a SLOB build still
has basic bounds checking (which was my intention with that config),
and non-SLOB builds still get multi-page checking.

-Kees

-- 
Kees Cook
Nexus Security