[ +David ]
On 11/19/20 8:04 AM, xiakaixu1987@xxxxxxxxx wrote:
From: Kaixu Xia <kaixuxia@xxxxxxxxxxx>
The return value of dev_get_by_index_rcu() can be NULL, so here it
is need to check the return value and return error code if it is NULL.
Signed-off-by: Kaixu Xia <kaixuxia@xxxxxxxxxxx>
---
net/core/filter.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/core/filter.c b/net/core/filter.c
index 2ca5eecebacf..1263fe07170a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5573,6 +5573,8 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
struct net_device *dev;
dev = dev_get_by_index_rcu(net, params->ifindex);
+ if (unlikely(!dev))
+ return -EINVAL;
if (!is_skb_forwardable(dev, skb))
rc = BPF_FIB_LKUP_RET_FRAG_NEEDED;
The above logic is quite ugly anyway given we fetched the dev pointer already earlier
in bpf_ipv{4,6}_fib_lookup() and now need to redo it again ... so yeah there could be
a tiny race in here. We wanted do bring this logic closer to what XDP does anyway,
something like below, for example. David, thoughts? Thx
Subject: [PATCH] diff mtu check
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
---
net/core/filter.c | 22 +++++-----------------
1 file changed, 5 insertions(+), 17 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index 2ca5eecebacf..3bab0a97fa38 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5547,9 +5547,6 @@ static const struct bpf_func_proto bpf_xdp_fib_lookup_proto = {
BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
struct bpf_fib_lookup *, params, int, plen, u32, flags)
{
- struct net *net = dev_net(skb->dev);
- int rc = -EAFNOSUPPORT;
-
if (plen < sizeof(*params))
return -EINVAL;
@@ -5559,25 +5556,16 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb,
switch (params->family) {
#if IS_ENABLED(CONFIG_INET)
case AF_INET:
- rc = bpf_ipv4_fib_lookup(net, params, flags, false);
- break;
+ return bpf_ipv4_fib_lookup(dev_net(skb->dev), params, flags,
+ !skb_is_gso(skb));
#endif
#if IS_ENABLED(CONFIG_IPV6)
case AF_INET6:
- rc = bpf_ipv6_fib_lookup(net, params, flags, false);
- break;
+ return bpf_ipv6_fib_lookup(dev_net(skb->dev), params, flags,
+ !skb_is_gso(skb));
#endif
}
-
- if (!rc) {
- struct net_device *dev;
-
- dev = dev_get_by_index_rcu(net, params->ifindex);
- if (!is_skb_forwardable(dev, skb))
- rc = BPF_FIB_LKUP_RET_FRAG_NEEDED;
- }
-
- return rc;
+ return -EAFNOSUPPORT;
}
static const struct bpf_func_proto bpf_skb_fib_lookup_proto = {
--
2.21.0
