On Wed, 6 Mar 2019 12:10:38 +1100
Suraj Jitindar Singh <sjitindarsi...@gmail.com> wrote:
> Commit ddf35cf3764b ("powerpc: Use barrier_nospec in copy_from_user()")
> Added barrier_nospec before loading from user-controller pointers.
> The intention was to order the load from the potentially user-controlled
> pointer vs a previous branch based on an access_ok() check or similar.
>
> In order to achieve the same result, add a barrier_nospec to the
> raw_copy_in_user() function before loading from such a user-controlled
> pointer.
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsi...@gmail.com>
> ---
> arch/powerpc/include/asm/uaccess.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/powerpc/include/asm/uaccess.h
> b/arch/powerpc/include/asm/uaccess.h
> index e3a731793ea2..bb615592d5bb 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -306,6 +306,7 @@ extern unsigned long __copy_tofrom_user(void __user *to,
> static inline unsigned long
> raw_copy_in_user(void __user *to, const void __user *from, unsigned long n)
> {
> + barrier_nospec();
> return __copy_tofrom_user(to, from, n);
> }
> #endif /* __powerpc64__ */
Hello,
AFAICT this is not needed. The data cannot be used in the kernel without
subsequent copy_from_user which already has the nospec barrier.
Thanks
Michal
