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Date:   Wed, 13 Jun 2018 17:06:18 +0900
From:   Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     Toshiaki Makita <makita.toshiaki@....ntt.co.jp>,
        netdev@...r.kernel.org, Jesper Dangaard Brouer <brouer@...hat.com>
Subject: [PATCH bpf] xdp: Fix handling of devmap in generic XDP

Commit 67f29e07e131 ("bpf: devmap introduce dev_map_enqueue") changed
the return value type of __devmap_lookup_elem() from struct net_device *
to struct bpf_dtab_netdev * but forgot to modify generic XDP code
accordingly.
Thus generic XDP incorrectly used struct bpf_dtab_netdev where struct
net_device is expected, then skb->dev was set to invalid value.

Fixes: 67f29e07e131 ("bpf: devmap introduce dev_map_enqueue")
Signed-off-by: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
---
 include/linux/bpf.h    | 10 ++++++++++
 include/linux/filter.h | 16 ++++++++++++++++
 kernel/bpf/devmap.c    | 14 ++++++++++++++
 net/core/filter.c      | 21 ++++-----------------
 4 files changed, 44 insertions(+), 17 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 995c3b1..2fe3aa1 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -487,6 +487,7 @@ static inline void bpf_long_memcpy(void *dst, const void *src, u32 size)
 void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);
 
 /* Map specifics */
+struct sk_buff;
 struct xdp_buff;
 
 struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key);
@@ -494,6 +495,8 @@ static inline void bpf_long_memcpy(void *dst, const void *src, u32 size)
 void __dev_map_flush(struct bpf_map *map);
 int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
 		    struct net_device *dev_rx);
+int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
+			     struct bpf_prog *xdp_prog);
 
 struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key);
 void __cpu_map_insert_ctx(struct bpf_map *map, u32 index);
@@ -586,6 +589,13 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
 	return 0;
 }
 
+static inline int dev_map_generic_redirect(struct bpf_dtab_netdev *dst,
+					   struct sk_buff *skb,
+					   struct bpf_prog *xdp_prog)
+{
+	return 0;
+}
+
 static inline
 struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
 {
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 45fc0f5..8ddff1f 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -19,6 +19,7 @@
 #include <linux/cryptohash.h>
 #include <linux/set_memory.h>
 #include <linux/kallsyms.h>
+#include <linux/if_vlan.h>
 
 #include <net/sch_generic.h>
 
@@ -786,6 +787,21 @@ static inline bool bpf_dump_raw_ok(void)
 struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
 				       const struct bpf_insn *patch, u32 len);
 
+static inline int __xdp_generic_ok_fwd_dev(struct sk_buff *skb,
+					   struct net_device *fwd)
+{
+	unsigned int len;
+
+	if (unlikely(!(fwd->flags & IFF_UP)))
+		return -ENETDOWN;
+
+	len = fwd->mtu + fwd->hard_header_len + VLAN_HLEN;
+	if (skb->len > len)
+		return -EMSGSIZE;
+
+	return 0;
+}
+
 /* The pair of xdp_do_redirect and xdp_do_flush_map MUST be called in the
  * same cpu context. Further for best results no more than a single map
  * for the do_redirect/do_flush pair should be used. This limitation is
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index a7cc7b3..642c97f 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -345,6 +345,20 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
 	return bq_enqueue(dst, xdpf, dev_rx);
 }
 
+int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
+			     struct bpf_prog *xdp_prog)
+{
+	int err;
+
+	err = __xdp_generic_ok_fwd_dev(skb, dst->dev);
+	if (unlikely(err))
+		return err;
+	skb->dev = dst->dev;
+	generic_xdp_tx(skb, xdp_prog);
+
+	return 0;
+}
+
 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);
diff --git a/net/core/filter.c b/net/core/filter.c
index 3d9ba7e..e7f12e9 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3214,20 +3214,6 @@ int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
 }
 EXPORT_SYMBOL_GPL(xdp_do_redirect);
 
-static int __xdp_generic_ok_fwd_dev(struct sk_buff *skb, struct net_device *fwd)
-{
-	unsigned int len;
-
-	if (unlikely(!(fwd->flags & IFF_UP)))
-		return -ENETDOWN;
-
-	len = fwd->mtu + fwd->hard_header_len + VLAN_HLEN;
-	if (skb->len > len)
-		return -EMSGSIZE;
-
-	return 0;
-}
-
 static int xdp_do_generic_redirect_map(struct net_device *dev,
 				       struct sk_buff *skb,
 				       struct xdp_buff *xdp,
@@ -3256,10 +3242,11 @@ static int xdp_do_generic_redirect_map(struct net_device *dev,
 	}
 
 	if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
-		if (unlikely((err = __xdp_generic_ok_fwd_dev(skb, fwd))))
+		struct bpf_dtab_netdev *dst = fwd;
+
+		err = dev_map_generic_redirect(dst, skb, xdp_prog);
+		if (unlikely(err))
 			goto err;
-		skb->dev = fwd;
-		generic_xdp_tx(skb, xdp_prog);
 	} else if (map->map_type == BPF_MAP_TYPE_XSKMAP) {
 		struct xdp_sock *xs = fwd;
 
-- 
1.8.3.1


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