[PATCH nf 1/2] netfilter: nft_flow_offload: reset dst in route object after setting up flow

[PATCH nf 1/2] netfilter: nft_flow_offload: reset dst in route object after setting up flow

[Pablo Neira Ayuso]

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@netfilter.org>
---
 include/net/netfilter/nf_flow_table.h |  2 +-
 net/netfilter/nf_flow_table_core.c    | 16 +++++++++++++---
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index 956c752ceb31..a763dd327c6e 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -276,7 +276,7 @@ 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 920a5a29ae1d..7502d6d73a60 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -87,12 +87,22 @@ 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) {
@@ -146,7 +156,7 @@ 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);
-- 
2.30.2

[PATCH nf 2/2] netfilter: nft_flow_offload: release dst in case direct xmit path is used

[Pablo Neira Ayuso]

Direct xmit does not use it since it calls dev_queue_xmit() to send
packets, hence it calls dst_release().

kmemleak reports:

unreferenced object 0xffff88814f440900 (size 184):
  comm "softirq", pid 0, jiffies 4294951896
  hex dump (first 32 bytes):
    00 60 5b 04 81 88 ff ff 00 e6 e8 82 ff ff ff ff  .`[.............
    21 0b 50 82 ff ff ff ff 00 00 00 00 00 00 00 00  !.P.............
  backtrace (crc cb2bf5d6):
    [<000000003ee17107>] kmem_cache_alloc+0x286/0x340
    [<0000000021a5de2c>] dst_alloc+0x43/0xb0
    [<00000000f0671159>] rt_dst_alloc+0x2e/0x190
    [<00000000fe5092c9>] __mkroute_output+0x244/0x980
    [<000000005fb96fb0>] ip_route_output_flow+0xc0/0x160
    [<0000000045367433>] nf_ip_route+0xf/0x30
    [<0000000085da1d8e>] nf_route+0x2d/0x60
    [<00000000d1ecd1cb>] nft_flow_route+0x171/0x6a0 [nft_flow_offload]
    [<00000000d9b2fb60>] nft_flow_offload_eval+0x4e8/0x700 [nft_flow_offload]
    [<000000009f447dbb>] expr_call_ops_eval+0x53/0x330 [nf_tables]
    [<00000000072e1be6>] nft_do_chain+0x17c/0x840 [nf_tables]
    [<00000000d0551029>] nft_do_chain_inet+0xa1/0x210 [nf_tables]
    [<0000000097c9d5c6>] nf_hook_slow+0x5b/0x160
    [<0000000005eccab1>] ip_forward+0x8b6/0x9b0
    [<00000000553a269b>] ip_rcv+0x221/0x230
    [<00000000412872e5>] __netif_receive_skb_one_core+0xfe/0x110

Fixes: fa502c865666 ("netfilter: flowtable: simplify route logic")
Reported-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_flow_table_core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 7502d6d73a60..a0571339239c 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -132,6 +132,7 @@ static int flow_offload_fill_route(struct flow_offload *flow,
 		       ETH_ALEN);
 		flow_tuple->out.ifidx = route->tuple[dir].out.ifindex;
 		flow_tuple->out.hw_ifidx = route->tuple[dir].out.hw_ifindex;
+		dst_release(dst);
 		break;
 	case FLOW_OFFLOAD_XMIT_XFRM:
 	case FLOW_OFFLOAD_XMIT_NEIGH:
-- 
2.30.2