[v4 5/6] powerpc: add machine check safe copy_to_user

[Christophe Leroy]

Le 06/07/2019 à 11:46, Santosh Sivaraj a écrit :
> Use  memcpy_mcsafe() implementation to define copy_to_user_mcsafe()
> 
> Signed-off-by: Santosh Sivaraj <santosh at fossix.org>
> ---
>   arch/powerpc/Kconfig               |  1 +
>   arch/powerpc/include/asm/uaccess.h | 14 ++++++++++++++
>   2 files changed, 15 insertions(+)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 8c1c636308c8..a173b392c272 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -134,6 +134,7 @@ config PPC
>   	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
>   	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_HAS_UACCESS_FLUSHCACHE	if PPC64
> +	select ARCH_HAS_UACCESS_MCSAFE		if PPC64
>   	select ARCH_HAS_UBSAN_SANITIZE_ALL
>   	select ARCH_HAS_ZONE_DEVICE		if PPC_BOOK3S_64
>   	select ARCH_HAVE_NMI_SAFE_CMPXCHG
> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
> index 76f34346b642..8899864a5552 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -386,6 +386,20 @@ static inline unsigned long raw_copy_to_user(void __user *to,
>   	return ret;
>   }
>   
> +static __always_inline unsigned long __must_check
> +copy_to_user_mcsafe(void __user *to, const void *from, unsigned long n)
> +{
> +	if (likely(check_copy_size(from, n, true))) {
> +		if (access_ok(to, n)) {

After looking once more, it looks like copy_to_user_mcsafe() is only 
called from copyout_mcsafe(), so maybe this access_ok() check is 
superfluous.

> +			allow_write_to_user(to, n);
> +			n = memcpy_mcsafe((void *)to, from, n);
> +			prevent_write_to_user(to, n);
> +		}
> +	}
> +
> +	return n;

Shouldn't it return 0 when check_copy_size() fails ?

Christophe

> +}
> +
>   extern unsigned long __clear_user(void __user *addr, unsigned long size);
>   
>   static inline unsigned long clear_user(void __user *addr, unsigned long size)
>