Re: [PATCH] misc: Fix rare fortify crash on wchar funcs. [BZ 29030]

[Siddhesh Poyarekar <siddhesh@gotplt.org>]

On 18/04/2022 10:14, Siddhesh Poyarekar wrote:
>>         cp = "A";
>>         if (mbstowcs (wenough, cp, 10) != 1
>>         || wcscmp (wenough, L"A") != 0)
>> diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h
>> index 44d3826bca..b8419e7e6c 100644
>> --- a/misc/sys/cdefs.h
>> +++ b/misc/sys/cdefs.h
>> @@ -156,14 +156,14 @@
>>      variants.  These conditions should get evaluated to constant and 
>> optimized
>>      away.  */
>> -#define __glibc_safe_len_cond(__l, __s, __osz) ((__l) <= (__osz) / 
>> (__s))
>> +#define __glibc_safe_len_cond(__l, __s, __osz) \
>> +  ((__osz) == (size_t) -1 || ((__l) <= (__osz) / (__s)))
> 
> This should go...
> 
>>   #define __glibc_unsigned_or_positive(__l) \
>>     ((__typeof (__l)) 0 < (__typeof (__l)) -1                      \
>>      || (__builtin_constant_p (__l) && (__l) > 0))
>>   /* Length is known to be safe at compile time if the __L * __S <= 
>> __OBJSZ
>> -   condition can be folded to a constant and if it is true.  The -1 
>> check is
>> -   redundant because since it implies that __glibc_safe_len_cond is 
>> true.  */
>> +   condition can be folded to a constant and if it is true, or 
>> unknown (-1) */
>>   #define __glibc_safe_or_unknown_len(__l, __s, __osz) \
> 
> here since the above macro is "safe length condition" and this one is 
> "safe or unknown length", so the unknown length check ideally belongs here.

Sorry I missed another note, please use __SIZE_TYPE__ instead of size_t 
to avoid having to include stddef.h.

Thanks,
Siddhesh