bpf: Allow return values 0 and 1 for kprobe session

[ Upstream commit 17c4b65 ]

The kprobe session program can return only 0 or 1,
instruct verifier to check for that.

Fixes: 535a369 ("bpf: Add support for kprobe session attach")
Signed-off-by: Jiri Olsa <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
Signed-off-by: Sasha Levin <[email protected]>

Author: olsajiri

kernel/bpf/verifier.c

@@ -15988,6 +15988,15 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
 			return -ENOTSUPP;
 		}
 		break;
+	case BPF_PROG_TYPE_KPROBE:
+		switch (env->prog->expected_attach_type) {
+		case BPF_TRACE_KPROBE_SESSION:
+			range = retval_range(0, 1);
+			break;
+		default:
+			return 0;
+		}
+		break;
 	case BPF_PROG_TYPE_SK_LOOKUP:
 		range = retval_range(SK_DROP, SK_PASS);
 		break;