Messages in this thread | | | Date | Wed, 2 Mar 2016 15:43:58 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH 2/2] kasan: unpoison stack of idle task on cpu online |
| |
On Wed, Mar 02, 2016 at 06:27:49PM +0300, Andrey Ryabinin wrote: > On 03/02/2016 05:50 PM, Mark Rutland wrote: > > On Wed, Mar 02, 2016 at 04:51:59PM +0300, Andrey Ryabinin wrote:
[...]
> > Is all the above necessary? > > > > Surely we can just include <linux/smpboot.h> in mm/kasan/kasan.c? > > It is necessary. kernel/smpboot.h != include/linux/smpboot.h
Ah, I'd misread the patch. Sorry for the noise!
[...]
> >> + struct task_struct *tidle = idle_thread_get(cpu); > >> + kasan_unpoison_shadow(task_stack_page(tidle), THREAD_SIZE); > > > > We never expect the stack to hit the end of the thread_info, so we can > > start at task_stack_page(tidle) + 1, and avoid the shadow for > > sizeof(struct thread_info). > > > > I wouldn't bother, it's simpler to unpoison all. Size of struct thread_info is 32-bytes. That's 4-bytes of shadow. > I don't think it matters whether you do memset of 2048 or 2044 bytes. > > > Do we do any poisoning of the thread_info structure in the thread_union? > > No, why would we poison it? It's absolutely valid memory and available for access.
For some reason I thought ASAN might poison gaps between struct elements, or at least held open the option to. I guess inserting padding would be an ABI issue, so it probably doesn't.
In the absence of that, I agree that always starting at task_stack_page(t), and clearing the shadow for THREAD_SIZE bytes of stack makes sense).
Thanks, Mark.
| |