Re: [PATCH] IPv6: Fix NULL dereference in ipv6_del_addr()

[Ville Nuorvala <vnuorval@tcs.hut.fi>]

YOSHIFUJI Hideaki wrote:
> In article <455DB884.3050203@tcs.hut.fi> (at Fri, 17 Nov 2006 15:26:28 +0200), Ville Nuorvala <vnuorval@tcs.hut.fi> says:
> 
> 
>> -		dst_release(&rt->u.dst);
>> +		if (rt)
>> +			dst_release(&rt->u.dst);
>>  	}
> 
> I disagree.  This does NOT fix any bugs.
> 
> (void *)&rt->u.dst is ever equal to (void*)rt, and
> dst_release() checks if the argument is NULL.

As the check is unnecessary you probably want to clean up the other 
places where rt is checked before &rt->u.dst is passed, as well ;-)
This is done at least in addrconf.c, ndisc.c and route.c...

Seriously though, you are probably right about the pointer being equal 
to NULL in this case,  but does the C language actually guarantee that 
the pointer to the structure and its first element are equal, or is it 
implementation dependent? I don't have my K&R here, so I can't check.

Regards,
Ville