[systemd-devel] [PATCH 5/6] network: fix strict aliasing issue

[Shawn Landden]

On Sun, Apr 12, 2015 at 12:43 PM, Lennart Poettering
<lennart at poettering.net> wrote:
> On Wed, 11.03.15 08:13, Shawn Landden (shawn at churchofgit.com) wrote:
>
>> We shouldn't assume 64-bit arch with the way we do math either.
>> (although I will submit a patch to glibc to add a uint64_t union
>> alias)
>
> Hmm? uint64_t works fine on 32bit too. The compiler can do the
> necessary emulation on its own... I don't see the need to change
> anything here.
Its also an unaligned access. in_addr.in6 is only 32-bit aligned. (in
addition to being a strict aliasing violation.)
>
>> diff --git a/src/network/networkd-address.c b/src/network/networkd-address.c
>> index 0be6165..4b7f451 100644
>> --- a/src/network/networkd-address.c
>> +++ b/src/network/networkd-address.c
>> @@ -605,12 +605,12 @@ bool address_equal(Address *a1, Address *a2) {
>>                  }
>>
>>          case AF_INET6: {
>> -                uint64_t *b1, *b2;
>> +                uint32_t *b1, *b2;
>>
>> -                b1 = (uint64_t*)&a1->in_addr.in6;
>> -                b2 = (uint64_t*)&a2->in_addr.in6;
>> +                b1 = &a1->in_addr.in6.s6_addr32[0];
>> +                b2 = &a2->in_addr.in6.s6_addr32[0];
>>
>> -                return (((b1[0] ^ b2[0]) | (b1[1] ^ b2[1])) == 0UL);
>> +                return (((b1[0] ^ b2[0]) | (b1[1] ^ b2[1]) | (b1[2] ^ b2[2]) | (b1[3] ^  b2[3])) == 0);
>>          }
>>
>>          default:
>> --
>> 2.2.1.209.g41e5f3a
>>
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>
>
> Lennart
>
> --
> Lennart Poettering, Red Hat
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-- 
Shawn Landden