Commit e1ee3673 authored Jul 29, 2013 by Pablo Neira Committed by David S. Miller Jul 30, 2013

genetlink: fix usage of NLM_F_EXCL or NLM_F_REPLACE



Currently, it is not possible to use neither NLM_F_EXCL nor
NLM_F_REPLACE from genetlink. This is due to this checking in
genl_family_rcv_msg:

	if (nlh->nlmsg_flags & NLM_F_DUMP)

NLM_F_DUMP is NLM_F_MATCH|NLM_F_ROOT. Thus, if NLM_F_EXCL or
NLM_F_REPLACE flag is set, genetlink believes that you're
requesting a dump and it calls the .dumpit callback.

The solution that I propose is to refine this checking to
make it stricter:

	if ((nlh->nlmsg_flags & NLM_F_DUMP) == NLM_F_DUMP)

And given the combination NLM_F_REPLACE and NLM_F_EXCL does
not make sense to me, it removes the ambiguity.

There was a patch that tried to fix this some time ago (0ab03c2b
netlink: test for all flags of the NLM_F_DUMP composite) but it
tried to resolve this ambiguity in *all* existing netlink subsystems,
not only genetlink. That patch was reverted since it broke iproute2,
which is using NLM_F_ROOT to request the dump of the routing cache.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent ff862a46

net/netlink/genetlink.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -571,7 +571,7 @@ static int genl_family_rcv_msg(struct genl_family *family,
		!capable(CAP_NET_ADMIN))
		return -EPERM;

		if (nlh->nlmsg_flags & NLM_F_DUMP) {
		if ((nlh->nlmsg_flags & NLM_F_DUMP) == NLM_F_DUMP) {
		struct netlink_dump_control c = {
		.dump = ops->dumpit,
		.done = ops->done,

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