[cfe-dev] Security fail (memset being optimized away)

Jonny Grant via cfe-dev cfe-dev at lists.llvm.org
Fri Jan 4 06:47:44 PST 2019



On 04/01/2019 14:31, myLC at gmx.de wrote:
> On 1/4/19 1:47 PM, Jonny Grant wrote:
>> Why not just write an inline function which does after memset :-
>>
>> if(*buf!=0) *buf=0;
> 
> 
> This would only zero one byte, but it would get optimized away
> as the buffer goes out of scope (= is being discarded).

Maybe add an abort()  ?

eg

inline void check_memset(void *s, int c, size_t n);
{
     const char * buf = (char*)buf;
     memset(2, 0, n);

     if(0 != *buf)
     {
         abort();
     }
}




Or use a for loop to verify all bytes are now 0.

Jonny


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