[PATCH bpf] xdp: XDP_REDIRECT should check IFF_UP and MTU

[Toshiaki Makita]

Otherwise we end up with attempting to send packets from down devices
or to send oversized packets, which may cause unexpected driver/device
behaviour. Generic XDP has already done this check, so reuse the logic
in native XDP.

Fixes: 814abfabef3c ("xdp: add bpf_redirect helper function")
Signed-off-by: Toshiaki Makita <makita.toshi...@lab.ntt.co.jp>
---
 include/linux/filter.h | 6 +++---
 kernel/bpf/devmap.c    | 7 ++++++-
 net/core/filter.c      | 9 +++++++--
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 300baad..c73dd73 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -765,8 +765,8 @@ 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)
+static inline int xdp_ok_fwd_dev(const struct net_device *fwd,
+                                unsigned int pktlen)
 {
        unsigned int len;
 
@@ -774,7 +774,7 @@ static inline int __xdp_generic_ok_fwd_dev(struct sk_buff 
*skb,
                return -ENETDOWN;
 
        len = fwd->mtu + fwd->hard_header_len + VLAN_HLEN;
-       if (skb->len > len)
+       if (pktlen > len)
                return -EMSGSIZE;
 
        return 0;
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 642c97f..d361fc1 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -334,10 +334,15 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct 
xdp_buff *xdp,
 {
        struct net_device *dev = dst->dev;
        struct xdp_frame *xdpf;
+       int err;
 
        if (!dev->netdev_ops->ndo_xdp_xmit)
                return -EOPNOTSUPP;
 
+       err = xdp_ok_fwd_dev(dev, xdp->data_end - xdp->data);
+       if (unlikely(err))
+               return err;
+
        xdpf = convert_to_xdp_frame(xdp);
        if (unlikely(!xdpf))
                return -EOVERFLOW;
@@ -350,7 +355,7 @@ int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, 
struct sk_buff *skb,
 {
        int err;
 
-       err = __xdp_generic_ok_fwd_dev(skb, dst->dev);
+       err = xdp_ok_fwd_dev(dst->dev, skb->len);
        if (unlikely(err))
                return err;
        skb->dev = dst->dev;
diff --git a/net/core/filter.c b/net/core/filter.c
index 0ca6907..2303f73 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3046,12 +3046,16 @@ static int __bpf_tx_xdp(struct net_device *dev,
                        u32 index)
 {
        struct xdp_frame *xdpf;
-       int sent;
+       int err, sent;
 
        if (!dev->netdev_ops->ndo_xdp_xmit) {
                return -EOPNOTSUPP;
        }
 
+       err = xdp_ok_fwd_dev(dev, xdp->data_end - xdp->data);
+       if (unlikely(err))
+               return err;
+
        xdpf = convert_to_xdp_frame(xdp);
        if (unlikely(!xdpf))
                return -EOVERFLOW;
@@ -3285,7 +3289,8 @@ int xdp_do_generic_redirect(struct net_device *dev, 
struct sk_buff *skb,
                goto err;
        }
 
-       if (unlikely((err = __xdp_generic_ok_fwd_dev(skb, fwd))))
+       err = xdp_ok_fwd_dev(fwd, skb->len);
+       if (unlikely(err))
                goto err;
 
        skb->dev = fwd;
-- 
1.8.3.1