linux-kernel - Re: [PATCH v5 3/3] x86/sgx: Remove redundant if conditions in sgx_encl

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Date:   Wed, 24 Feb 2021 17:31:02 +0800
From:   Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Shuah Khan <shuah@...nel.org>, x86@...nel.org,
        linux-sgx@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jia Zhang <zhang.jia@...ux.alibaba.com>
Subject: Re: [PATCH v5 3/3] x86/sgx: Remove redundant if conditions in
 sgx_encl_create



On 2/16/21 4:29 PM, Jarkko Sakkinen wrote:
> On Tue, Feb 16, 2021 at 11:31:33AM +0800, Tianjia Zhang wrote:
>> In this scenario, there is no case where va_page is NULL, and
>> the error has been checked. The if-condition statement here is
>> redundant, so remove the condition detection.
>>
>> Signed-off-by: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
>> Acked-by: Jarkko Sakkinen <jarkko@...nel.org>
>> ---
>>   arch/x86/kernel/cpu/sgx/ioctl.c | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
>> index 1c6ecf9fbeff..719c21cca569 100644
>> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
>> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
>> @@ -66,9 +66,10 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs)
>>   	va_page = sgx_encl_grow(encl);
>>   	if (IS_ERR(va_page))
>>   		return PTR_ERR(va_page);
>> -	else if (va_page)
>> -		list_add(&va_page->list, &encl->va_pages);
>> -	/* else the tail page of the VA page list had free slots. */
>> +	if (!va_page)
>> +		return -EIO;
> 
> Why this check?
> 

The value of va_page may be a negative error value, it may be NULL, or 
it may be a valid pointer, so check this return value.

Tianjia

>> +
>> +	list_add(&va_page->list, &encl->va_pages);
>>   
>>   	/* The extra page goes to SECS. */
>>   	encl_size = secs->size + PAGE_SIZE;
>> -- 
>> 2.19.1.3.ge56e4f7
>>
>>
> 
> /Jarkko
>