[PATCH] Give a useful meaning to arc4random_uniform(0);

[Alejandro Colomar]

On 12/31/22 16:13, Alejandro Colomar wrote:
> Hi Theo,
> 
> On 12/31/22 15:56, Alejandro Colomar wrote:
>>>
>>> I do not like your proposal at all.  A function like arc4random_range()
>>> is even more likely to be used wrong by passing backwards points
>>> and you seem to have a lot of hubris to add a range check to it.
> 
> I didn't understand the entire sentence, since I'm not a native English speaker. 
>   Sorry for that.  About adding a range check, I'm not against it.  But what to 
> do in that case?  abort()?  I don't see anything significantly better?  In the 

s/better?/better./

> Linux kernel, the used something BUILD_BUG, but I don't know those macros very 

s/the used/they used/

Sorry for the typos.

> much.
> 
> I'm really open to discussion about what would the the best behavior when max < 
> min.
> 
> Cheers,
> 
> Alex
> 
>>
>> Oh, I just checked hubris in the dictionary and it seems you did mention ego. 
>> I'll try to rebate you with something useful.
>>
>> If you run `grep -rn 'arc4random_uniform('` in the OpenBSD tree, there will be 
>> many cases where you'd really benefit from this.  I'll just pick a few:
>>
>>
>> sys/net/pf_lb.c:224:
>>              cut = arc4random_uniform(1 + high - low) + low;
>> better as:
>>              cut = arc4random_range(low, high);
>>
>>
>> sys/kern/kern_fork.c:648:
>>          pid = 2 + arc4random_uniform(PID_MAX - 1);
>> better as:
>>          pid = arc4random_range(2, PID_MAX);
>>
>>
>> usr.bin/nc/netcat.c:1501:
>>                  cp = arc4random_uniform(x + 1);
>> better as:
>>                  cp = arc4random_range(0, x);
>>
>>

-- 
<http://www.alejandro-colomar.es/>
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