linux-kernel - Re: [PATCH] kselftest: vDSO: Fix accumulation of uninitialized ret when CLOCK

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Message-ID: <530b12f1-b0d2-1183-c9a9-0f5f9d6e178d@gmail.com>
Date:   Tue, 18 Apr 2023 11:14:20 +0100
From:   "Colin King (gmail)" <colin.i.king@...il.com>
To:     Vincenzo Frascino <vincenzo.frascino@....com>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kselftest@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kselftest: vDSO: Fix accumulation of uninitialized ret
 when CLOCK_REALTIME is undefined

On 18/04/2023 11:10, Vincenzo Frascino wrote:
> Hi Colin,
> 
> On 4/17/23 11:47, Colin Ian King wrote:
>> In the unlikely case that CLOCK_REALTIME is not defined, variable ret is
>> not initialized and further accumulation of return values to ret can leave
>> ret in an undefined state. Fix this by initialized ret to zero and changing
>> the assignment of ret to an accumulation for the CLOCK_REALTIME case.
>>
> 
> I was wondering how did you find this.

I used cppcheck --force --enable=all, this examines the #if defined() paths.

> 
> Apart that:
> 
> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@....com>
> 
>> Fixes: 03f55c7952c9 ("kselftest: Extend vDSO selftest to clock_getres")
>> Signed-off-by: Colin Ian King <colin.i.king@...il.com>
>> ---
>>   tools/testing/selftests/vDSO/vdso_test_clock_getres.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/testing/selftests/vDSO/vdso_test_clock_getres.c b/tools/testing/selftests/vDSO/vdso_test_clock_getres.c
>> index 15dcee16ff72..38d46a8bf7cb 100644
>> --- a/tools/testing/selftests/vDSO/vdso_test_clock_getres.c
>> +++ b/tools/testing/selftests/vDSO/vdso_test_clock_getres.c
>> @@ -84,12 +84,12 @@ static inline int vdso_test_clock(unsigned int clock_id)
>>   
>>   int main(int argc, char **argv)
>>   {
>> -	int ret;
>> +	int ret = 0;
>>   
>>   #if _POSIX_TIMERS > 0
>>   
>>   #ifdef CLOCK_REALTIME
>> -	ret = vdso_test_clock(CLOCK_REALTIME);
>> +	ret += vdso_test_clock(CLOCK_REALTIME);
>>   #endif
>>   
>>   #ifdef CLOCK_BOOTTIME
>