netdev - [PATCH bpf-next] bpf: Enforce 'return 0' in BTF-enabled raw

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Date:   Mon, 28 Oct 2019 20:24:26 -0700
From:   Alexei Starovoitov <ast@...nel.org>
To:     <davem@...emloft.net>
CC:     <daniel@...earbox.net>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>, <kernel-team@...com>
Subject: [PATCH bpf-next] bpf: Enforce 'return 0' in BTF-enabled raw_tp programs

The return value of raw_tp programs is ignored by __bpf_trace_run()
that calls them. The verifier also allows any value to be returned.
For BTF-enabled raw_tp lets enforce 'return 0', so that return value
can be used for something in the future.

Signed-off-by: Alexei Starovoitov <ast@...nel.org>
---
 kernel/bpf/verifier.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c59778c0fc4d..6b0de04f8b91 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6279,6 +6279,11 @@ static int check_return_code(struct bpf_verifier_env *env)
 	case BPF_PROG_TYPE_CGROUP_SYSCTL:
 	case BPF_PROG_TYPE_CGROUP_SOCKOPT:
 		break;
+	case BPF_PROG_TYPE_RAW_TRACEPOINT:
+		if (!env->prog->aux->attach_btf_id)
+			return 0;
+		range = tnum_const(0);
+		break;
 	default:
 		return 0;
 	}
-- 
2.17.1