Re: af_unix unix_getname: return size for unnamed sockets too small?

Marcus Meissner [off-list ref] writes:

Hi,

In net/unix/af_unix.c::unix_getname() there is a small problem:

        if (!u->addr) {
                sunaddr->sun_family = AF_UNIX;
                sunaddr->sun_path[0] = 0;		// not copied out
                *uaddr_len = sizeof(short);
        } else {
                struct unix_address *addr = u->addr;

                *uaddr_len = addr->len;
                memcpy(sunaddr, addr->name, *uaddr_len);
        }

The if (!u->addr) case will not copy out the \0 in the sun_path, as
uaddr_len is just the size of sun_family.

(Shown by socat crashing after decoding gethostname return and expected
sun_path to be a valid string (and not seeing the \0)).

Perhaps my memory is scrambled but the sun_path has embedded '\0's so I
don't see how a correct application can expect the path to be '\0'
terminated.  An application should be looking at the length we give it.

Should it perhaps be *uaddr_len = sizeof(short)+sizeof(char)?

I don't think so.

Eric