Patch "mctp: Allow local delivery to the null EID" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    mctp: Allow local delivery to the null EID

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mctp-allow-local-delivery-to-the-null-eid.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 024b1876fc209d4c97e38a74ba548ee32f8c34b9
Author: Jeremy Kerr <jk@xxxxxxxxxxxxxxxxxxxx>
Date:   Wed Sep 29 15:26:06 2021 +0800

    mctp: Allow local delivery to the null EID
    
    [ Upstream commit 1f6c77ac9e6ecef152fd5df94c4b3c346adb197a ]
    
    We may need to receive packets addressed to the null EID (==0), but
    addressed to us at the physical layer.
    
    This change adds a lookup for local routes when we see a packet
    addressed to EID 0, and a local phys address.
    
    Signed-off-by: Jeremy Kerr <jk@xxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Stable-dep-of: 5093bbfc10ab ("mctp: perform route lookups under a RCU read-side lock")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/mctp/route.c b/net/mctp/route.c
index 89e67399249b4..859f57fd3871f 100644
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -480,6 +480,10 @@ static int mctp_alloc_local_tag(struct mctp_sock *msk,
 	int rc = -EAGAIN;
 	u8 tagbits;
 
+	/* for NULL destination EIDs, we may get a response from any peer */
+	if (daddr == MCTP_ADDR_NULL)
+		daddr = MCTP_ADDR_ANY;
+
 	/* be optimistic, alloc now */
 	key = mctp_key_alloc(msk, saddr, daddr, 0, GFP_KERNEL);
 	if (!key)
@@ -558,6 +562,20 @@ struct mctp_route *mctp_route_lookup(struct net *net, unsigned int dnet,
 	return rt;
 }
 
+static struct mctp_route *mctp_route_lookup_null(struct net *net,
+						 struct net_device *dev)
+{
+	struct mctp_route *rt;
+
+	list_for_each_entry_rcu(rt, &net->mctp.routes, list) {
+		if (rt->dev->dev == dev && rt->type == RTN_LOCAL &&
+		    refcount_inc_not_zero(&rt->refs))
+			return rt;
+	}
+
+	return NULL;
+}
+
 /* sends a skb to rt and releases the route. */
 int mctp_do_route(struct mctp_route *rt, struct sk_buff *skb)
 {
@@ -853,6 +871,11 @@ static int mctp_pkttype_receive(struct sk_buff *skb, struct net_device *dev,
 	rcu_read_unlock();
 
 	rt = mctp_route_lookup(net, cb->net, mh->dest);
+
+	/* NULL EID, but addressed to our physical address */
+	if (!rt && mh->dest == MCTP_ADDR_NULL && skb->pkt_type == PACKET_HOST)
+		rt = mctp_route_lookup_null(net, dev);
+
 	if (!rt)
 		goto err_drop;