Messages in this thread | | | Date | Fri, 2 Dec 2016 15:57:38 -0600 | From | Josh Poimboeuf <> | Subject | Re: [PATCH v4] x86/suspend: fix false positive KASAN warning on suspend/resume |
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On Fri, Dec 02, 2016 at 10:09:03PM +0100, Pavel Machek wrote: > On Fri 2016-12-02 11:42:21, Josh Poimboeuf wrote: > > Resuming from a suspend operation is showing a KASAN false positive > > warning: > > > > > > Reported-by: Scott Bauer <scott.bauer@intel.com> > > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> > > Acked-by: Pavel Machek <pavel@ucw.cz> > > > diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c > > index 0e9505f..b2a0cff 100644 > > --- a/mm/kasan/kasan.c > > +++ b/mm/kasan/kasan.c > > @@ -80,7 +80,14 @@ void kasan_unpoison_task_stack(struct task_struct *task) > > /* Unpoison the stack for the current task beyond a watermark sp value. */ > > asmlinkage void kasan_unpoison_task_stack_below(const void *watermark) > > { > > - __kasan_unpoison_stack(current, watermark); > > + /* > > + * Calculate the task stack base address. Avoid using 'current' > > + * because this function is called by early resume code which hasn't > > + * yet set up the percpu register (%gs). > > + */ > > + void *base = (void *)((unsigned long)watermark & ~(THREAD_SIZE - 1)); > > + > > + kasan_unpoison_shadow(base, watermark - base); > > } > > > > I know you modified this code to be arch-independend... but is it > really? I guess it is portable enough across architectures that run > kasan today..
Yes, it's arch-independent as far as I know.
All the implementations of alloc_thread_stack_node() in kernel/fork.c create THREAD_SIZE sized/aligned stacks.
ia64 has its own implementation of alloc_thread_stack_node(), which also has a THREAD_SIZE sized/aligned stack, with task_struct stored at the beginning.
For those architectures for which stack grows up, they would need to call a different helper which unpoisons the stack above the watermark, but that was also the case before my patch.
-- Josh
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