RFR(S): 8252407: Build failure with gcc-8+ and asan

[Kim Barrett]

> On Sep 4, 2020, at 7:50 AM, Florian Weimer <fweimer at redhat.com> wrote:
> 
> * Daniel Fuchs:
> 
>> Hi,
>> 
>> On 02/09/2020 08:19, Florian Weimer wrote:
>>> At least one of the bugs was in theory user-visible: the network
>>> interface code would return data for an interface that does not actually
>>> exist on the system.
>> 
>> WRT NetworkInterface.c, I might support using `strnlen` to check
>> the length before hand, if that solves both cases (gcc8 and gcc10).
>> I'm always a bit nervous of changing the behavior in this library
>> as it's hard to verify that no regression is introduced.
> 
> I think you should use strlen.  If the string is longer than the buffer
> sent to the kernel, it cannot match an existing interface because all
> the names are shorter.  So some sort of “not found” error needs to
> reported.

That may be, but I think doing so probably won't do anything to
address the -Wstringop-truncation warnings.

> (I assume that it's actually a bug that you can look up a network
> interface by a name that merely shares the same prefix with an actual
> interface on the system.)
> 
> Thanks,
> Florian