[PATCH RESEND 1/8] netlink: call get_fd_nl_family before decode nlmsghdr

[JingPiao Chen]

On Sun, Aug 06, 2017 at 02:10:16AM +0300, Dmitry V. Levin wrote:
> On Tue, Aug 01, 2017 at 07:48:41AM +0800, JingPiao Chen wrote:
> > Prepare for NETLINK_KOBJECT_UEVENT decode. The messages
> > of NETLINK_KOBJECT_UEVENT do not contain nlmsghdr.
> [...]
> > (decode_nlmsghdr_with_payload): Skip family specific decoders
> > for type < NLMSG_MIN_TYPE && type != NLMSG_DONE.
> [...]
> > @@ -182,7 +177,7 @@ decode_nlmsg_type(const uint16_t type, const unsigned int family)
> >  	const struct xlat *xlat = netlink_types;
> >  	const char *dflt = "NLMSG_???";
> >  
> > -	if (type != NLMSG_DONE && family < ARRAY_SIZE(nlmsg_types)) {
> > +	if (type >= NLMSG_MIN_TYPE && family < ARRAY_SIZE(nlmsg_types)) {
> 
> Why?  How this is related to the rest of NETLINK_KOBJECT_UEVENT change?

Previous code when type < NLMSG_MIN_TYPE && type != NLMSG_DONE,
family = -2 (NL_FAMILY_DEFAULT), family < ARRAY_SIZE(nlmsg_types) filter
this case. Now get family ignore the nlmsg_type.
When type < NLMSG_MIN_TYPE && type != NLMSG_DONE, family is not
a negative. family < ARRAY_SIZE(nlmsg_types) can not filter this case.

Related commit:
v4.17-43-g1b63425, v4.17-44-g8700030: These commit introduce get_fd_nl_family.
And get family only when type >= NLMSG_MIN_TYPE.

v4.17-123-g54aed21: This commit changed get family when
type >= NLMSG_MIN_TYPE || type == NLMSG_DONE.

--
JingPiao Chen