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.
> ---
>
> 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
>
