bpf: verifier: avoid fall-through warnings

In preparation to enabling -Wimplicit-fallthrough, this patch silences the following warning:

kernel/bpf/verifier.c: In function ‘check_return_code’:
kernel/bpf/verifier.c:6106:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
if (env->prog->expected_attach_type == BPF_CGROUP_UDP4_RECVMSG ||

      ^

kernel/bpf/verifier.c:6109:2: note: here
case BPF_PROG_TYPE_CGROUP_SKB:
^~~~

Warning level 3 was used: -Wimplicit-fallthrough=3

Notice that is much clearer to explicitly add breaks in each case statement (that actually contains some code), rather than letting the code to fall through.

This patch is part of the ongoing efforts to enable -Wimplicit-fallthrough.

---

NOTE: -Wimplicit-fallthrough will be enabled globally in v5.3. So, I
suggest you to take this patch for 5.3-rc1.

 kernel/bpf/verifier.c | 2 ++
 1 file changed, 2 insertions(+)

index a2e763703c30..44c3b947400e 100644
@@ -6106,11 +6106,13 @@ static int check_return_code(struct bpf_verifier_env *env)
 		if (env->prog->expected_attach_type == BPF_CGROUP_UDP4_RECVMSG ||
 		    env->prog->expected_attach_type == BPF_CGROUP_UDP6_RECVMSG)
 			range = tnum_range(1, 1);
+		break;
 	case BPF_PROG_TYPE_CGROUP_SKB:
 		if (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS) {
 			range = tnum_range(0, 3);
 			enforce_attach_type_range = tnum_range(2, 3);
 		}
+		break;
 	case BPF_PROG_TYPE_CGROUP_SOCK:
 	case BPF_PROG_TYPE_SOCK_OPS:
 	case BPF_PROG_TYPE_CGROUP_DEVICE:

2.21.0

Looks good, applied to bpf, thanks.

Awesome. :)

Thanks, Daniel.
--
Gustavo