Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Santosh Sivaraj <santosh@fossix.org>
To:     Balbir Singh <bsingharora@gmail.com>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>
Cc:     "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Mahesh Salgaonkar <mahesh@linux.ibm.com>,
        Reza Arbab <arbab@linux.ibm.com>,
        Chandan Rajendra <chandan@linux.vnet.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        christophe leroy <christophe.leroy@c-s.fr>
Subject: Re: [PATCH v9 7/7] powerpc: add machine check safe copy_to_user
In-Reply-To: <74d12529-d068-0210-e229-5cea68bcf9da@gmail.com>
References: <20190812092236.16648-1-santosh@fossix.org> <20190812092236.16648-8-santosh@fossix.org> <74d12529-d068-0210-e229-5cea68bcf9da@gmail.com>
Date:   Thu, 15 Aug 2019 05:37:24 +0530
Message-ID: <874l2jqojn.fsf@santosiv.in.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Balbir,

Balbir Singh <bsingharora@gmail.com> 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 <santosh@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 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)
>>