Patch "netfilter: nft_flow_offload: reset dst in route object after setting up flow" 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

    netfilter: nft_flow_offload: reset dst in route object after setting up flow

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:
     netfilter-nft_flow_offload-reset-dst-in-route-object.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 67192824e8b46b1cf78a458c16c895eff9bff797
Author: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Date:   Wed Feb 21 12:32:58 2024 +0100

    netfilter: nft_flow_offload: reset dst in route object after setting up flow
    
    [ Upstream commit 9e0f0430389be7696396c62f037be4bf72cf93e3 ]
    
    dst is transferred to the flow object, route object does not own it
    anymore.  Reset dst in route object, otherwise if flow_offload_add()
    fails, error path releases dst twice, leading to a refcount underflow.
    
    Fixes: a3c90f7a2323 ("netfilter: nf_tables: flow offload expression")
    Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index 7677aacf72002..dabd84fa3fd36 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -258,7 +258,7 @@ nf_flow_table_offload_del_cb(struct nf_flowtable *flow_table,
 }
 
 void flow_offload_route_init(struct flow_offload *flow,
-			     const struct nf_flow_route *route);
+			     struct nf_flow_route *route);
 
 int flow_offload_add(struct nf_flowtable *flow_table, struct flow_offload *flow);
 void flow_offload_refresh(struct nf_flowtable *flow_table,
diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 4e0a2d47f6a6b..a213a7cb80435 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -86,12 +86,22 @@ static u32 flow_offload_dst_cookie(struct flow_offload_tuple *flow_tuple)
 	return 0;
 }
 
+static struct dst_entry *nft_route_dst_fetch(struct nf_flow_route *route,
+					     enum flow_offload_tuple_dir dir)
+{
+	struct dst_entry *dst = route->tuple[dir].dst;
+
+	route->tuple[dir].dst = NULL;
+
+	return dst;
+}
+
 static int flow_offload_fill_route(struct flow_offload *flow,
-				   const struct nf_flow_route *route,
+				   struct nf_flow_route *route,
 				   enum flow_offload_tuple_dir dir)
 {
 	struct flow_offload_tuple *flow_tuple = &flow->tuplehash[dir].tuple;
-	struct dst_entry *dst = route->tuple[dir].dst;
+	struct dst_entry *dst = nft_route_dst_fetch(route, dir);
 	int i, j = 0;
 
 	switch (flow_tuple->l3proto) {
@@ -145,7 +155,7 @@ static void nft_flow_dst_release(struct flow_offload *flow,
 }
 
 void flow_offload_route_init(struct flow_offload *flow,
-			    const struct nf_flow_route *route)
+			     struct nf_flow_route *route)
 {
 	flow_offload_fill_route(flow, route, FLOW_OFFLOAD_DIR_ORIGINAL);
 	flow_offload_fill_route(flow, route, FLOW_OFFLOAD_DIR_REPLY);