On Mon, Dec 2, 2019 at 11:08 AM Marco Elver <elver@xxxxxxxxxx> wrote:
>
> On Fri, 22 Nov 2019 at 12:27, <glider@xxxxxxxxxx> wrote:
> >
> > To avoid false positives, assume that reading from the task stack
> > always produces initialized values.
> >
> > Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
> > To: Alexander Potapenko <glider@xxxxxxxxxx>
> > Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
> > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> > Cc: linux-mm@xxxxxxxxx
>
> Acked-by: Marco Elver <elver@xxxxxxxxxx>
>
> assuming previous patch's include for kmsan-checks.h is added.
Yes, I'll add that include here as well in v4.
> > ---
> >
> > Change-Id: Ie73e5a41fdc8195699928e65f5cbe0d3d3c9e2fa
> > ---
> > arch/x86/include/asm/unwind.h | 9 +++++----
> > 1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
> > index 499578f7e6d7..f60c2bd1ddf2 100644
> > --- a/arch/x86/include/asm/unwind.h
> > +++ b/arch/x86/include/asm/unwind.h
> > @@ -100,9 +100,10 @@ void unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
> > #endif
> >
> > /*
> > - * This disables KASAN checking when reading a value from another task's stack,
> > - * since the other task could be running on another CPU and could have poisoned
> > - * the stack in the meantime.
> > + * This disables KASAN/KMSAN checking when reading a value from another task's
> > + * stack, since the other task could be running on another CPU and could have
> > + * poisoned the stack in the meantime. Frame pointers are uninitialized by
> > + * default, so for KMSAN we mark the return value initialized unconditionally.
> > */
> > #define READ_ONCE_TASK_STACK(task, x) \
> > ({ \
> > @@ -111,7 +112,7 @@ void unwind_module_init(struct module *mod, void *orc_ip, size_t orc_ip_size,
> > val = READ_ONCE(x); \
> > else \
> > val = READ_ONCE_NOCHECK(x); \
> > - val; \
> > + KMSAN_INIT_VALUE(val); \
> > })
> >
> > static inline bool task_on_another_cpu(struct task_struct *task)
> > --
> > 2.24.0.432.g9d3f5f5b63-goog
> >
--
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
