Re: [PATCH v9 7/7] powerpc: add machine check safe copy_to_user

[Santosh Sivaraj]

Hi Balbir,

Balbir Singh  writes:

> On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
>> Use  memcpy_mcsafe() implementation to define copy_to_user_mcsafe()
>> 
>> Signed-off-by: Santosh Sivaraj 
>> ---
>>  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 77f6ebf97113..4316e36095a2 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -137,6 +137,7 @@ 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_HAVE_NMI_SAFE_CMPXCHG
>>  select ARCH_KEEP_MEMBLOCK
>> diff --git a/arch/powerpc/include/asm/uaccess.h 
>> b/arch/powerpc/include/asm/uaccess.h
>> index 8b03eb44e876..15002b51ff18 100644
>> --- a/arch/powerpc/include/asm/uaccess.h
>> +++ b/arch/powerpc/include/asm/uaccess.h
>> @@ -387,6 +387,20 @@ 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)) {
>> +allow_write_to_user(to, n);
>> +n = memcpy_mcsafe((void *)to, from, n);
>> +prevent_write_to_user(to, n);
>> +}
>> +}
>> +
>> +return n;
>
> Do we always return n independent of the check_copy_size return value and
> access_ok return values?

Yes we always return the remaining bytes not copied even if check_copy_size
or access_ok fails.

Santosh

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

Re: [PATCH v9 7/7] powerpc: add machine check safe copy_to_user

[Balbir Singh]

On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
> Use  memcpy_mcsafe() implementation to define copy_to_user_mcsafe()
> 
> Signed-off-by: Santosh Sivaraj 
> ---
>  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 77f6ebf97113..4316e36095a2 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -137,6 +137,7 @@ 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_HAVE_NMI_SAFE_CMPXCHG
>   select ARCH_KEEP_MEMBLOCK
> diff --git a/arch/powerpc/include/asm/uaccess.h 
> b/arch/powerpc/include/asm/uaccess.h
> index 8b03eb44e876..15002b51ff18 100644
> --- a/arch/powerpc/include/asm/uaccess.h
> +++ b/arch/powerpc/include/asm/uaccess.h
> @@ -387,6 +387,20 @@ 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)) {
> + allow_write_to_user(to, n);
> + n = memcpy_mcsafe((void *)to, from, n);
> + prevent_write_to_user(to, n);
> + }
> + }
> +
> + return n;

Do we always return n independent of the check_copy_size return value and 
access_ok return values?

Balbir Singh.

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