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[-stable-4.1,-stable-4.2] netfilter: nfnetlink: work around wrong endianess in res_id field

Message ID 1441976447-8338-5-git-send-email-pablo@netfilter.org
State Awaiting Upstream
Delegated to: Pablo Neira
Headers show

Commit Message

Pablo Neira Ayuso Sept. 11, 2015, 1 p.m. UTC
[ upstream commit a9de9777d613500b089a7416f936bf3ae5f070d2 ]

The convention in nfnetlink is to use network byte order in every header field
as well as in the attribute payload. The initial version of the batching
infrastructure assumes that res_id comes in host byte order though.

The only client of the batching infrastructure is nf_tables, so let's add a
workaround to address this inconsistency. We currently have 11 nfnetlink
subsystems according to NFNL_SUBSYS_COUNT, so we can assume that the subsystem
2560, ie. htons(10), will not be allocated anytime soon, so it can be an alias
of nf_tables from the nfnetlink batching path when interpreting the res_id
field.

Based on original patch from Florian Westphal.

Cc: <stable@vger.kernel.org> # 4.1.x
Cc: <stable@vger.kernel.org> # 4.2.x
Reported-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nfnetlink.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)
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Patch

diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
index 0c0e8ec..70277b1 100644
--- a/net/netfilter/nfnetlink.c
+++ b/net/netfilter/nfnetlink.c
@@ -444,6 +444,7 @@  done:
 static void nfnetlink_rcv(struct sk_buff *skb)
 {
 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
+	u_int16_t res_id;
 	int msglen;
 
 	if (nlh->nlmsg_len < NLMSG_HDRLEN ||
@@ -468,7 +469,12 @@  static void nfnetlink_rcv(struct sk_buff *skb)
 
 		nfgenmsg = nlmsg_data(nlh);
 		skb_pull(skb, msglen);
-		nfnetlink_rcv_batch(skb, nlh, nfgenmsg->res_id);
+		/* Work around old nft using host byte order */
+		if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
+			res_id = NFNL_SUBSYS_NFTABLES;
+		else
+			res_id = ntohs(nfgenmsg->res_id);
+		nfnetlink_rcv_batch(skb, nlh, res_id);
 	} else {
 		netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 	}