Hello Joe Stringer,
Commit de375f4e91e3 ("selftests/bpf: Add C tests for reference
tracking") from Oct 2, 2018 (linux-next), leads to the following
Smatch static checker warning:
./tools/testing/selftests/bpf/progs/test_sk_lookup_kern.c:70
sk_lookup_success()
warn: potential pointer math issue ('tuple' is a 288 bit pointer)
./tools/testing/selftests/bpf/progs/test_sk_lookup_kern.c
55 SEC("?tc")
56 int sk_lookup_success(struct __sk_buff *skb)
57 {
58 void *data_end = (void *)(long)skb->data_end;
59 void *data = (void *)(long)skb->data;
60 struct ethhdr *eth = (struct ethhdr *)(data);
61 struct bpf_sock_tuple *tuple;
62 struct bpf_sock *sk;
63 size_t tuple_len;
64 bool ipv4;
65
66 if (eth + 1 > data_end)
67 return TC_ACT_SHOT;
68
69 tuple = get_tuple(data, sizeof(*eth), data_end, eth->h_proto,
&ipv4);
--> 70 if (!tuple || tuple + sizeof *tuple > data_end)
^^^^^^^^^^^^^^^^^^^^^
This is pointer math. It should be "tuple + 1" or (u8 *)tuple + sizeof(*tuple).
71 return TC_ACT_SHOT;
72
73 tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6);
74 sk = bpf_sk_lookup_tcp(skb, tuple, tuple_len,
BPF_F_CURRENT_NETNS, 0);
75 bpf_printk("sk=%d\n", sk ? 1 : 0);
76 if (sk)
77 bpf_sk_release(sk);
78 return sk ? TC_ACT_OK : TC_ACT_UNSPEC;
79 }
regards,
dan carpenter
