Re: [dpdk-dev] [PATCH] mem: fix overflowed return value

["Mrzyglod, DanielX T" <danielx.t.mrzyglod@intel.com>]

>-----Original Message-----
>From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen Hemminger
>Sent: Friday, April 22, 2016 6:25 PM
>To: Kobylinski, MichalX <michalx.kobylinski@intel.com>
>Cc: thomas.monjalon@6wind.com; dev@dpdk.org
>Subject: Re: [dpdk-dev] [PATCH] mem: fix overflowed return value
>
>On Fri, 22 Apr 2016 12:44:18 +0200
>Michal Kobylinski <michalx.kobylinski@intel.com> wrote:
>
>> Fix issue reported by Coverity.
>>
>> Coverity ID 13255: Overflowed return value: The return value will be too
>> small or even negative, likely resulting in unexpected behavior in a
>> caller that uses the return value. In rte_mem_virt2phy: An integer
>> overflow occurs, with the overflowed value used as the return value of
>> the function
>>
>> Fixes: 3097de6e6bfb ("mem: get physical address of any pointer")
>>
>> Signed-off-by: Michal Kobylinski <michalx.kobylinski@intel.com>
>> ---
>>  lib/librte_eal/linuxapp/eal/eal_memory.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c
>b/lib/librte_eal/linuxapp/eal/eal_memory.c
>> index 5b9132c..6ceca5b 100644
>> --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
>> +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
>> @@ -195,7 +195,7 @@ rte_mem_virt2phy(const void *virtaddr)
>>  	 * the pfn (page frame number) are bits 0-54 (see
>>  	 * pagemap.txt in linux Documentation)
>>  	 */
>> -	physaddr = ((page & 0x7fffffffffffffULL) * page_size)
>> +	physaddr = (uint64_t)((page & 0x7fffffffffffffULL) * page_size)
>>  		+ ((unsigned long)virtaddr % page_size);
>>  	close(fd);
>>  	return physaddr;
>
>I am not trusting any of these Coverity patches you are sending.
>It seems you think wraparound can be just fixed by casting, it can't

>From my point of view it's False Possitive there is no chance that page_size will be bigger than  long.
Coverity Assume that page_size may be 18446744071562067968 but it can't.

Only for glibc<2.1 we probably should change page_size = getpagesize();   to  page_size = sysconf(_SC_PAGESIZE); 
May I change this Coverity to False Positive or I missed something ? What's your opinion ?