fix a verifier bug in check_attach_btf_id()

index a0482e1c4a77..034ef81f935b 100644
@@ -9636,7 +9636,10 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
 				ret = -EINVAL;
 				goto out;
 			}
-			addr = (long) tgt_prog->aux->func[subprog]->bpf_func;
+			if (subprog == 0)
+				addr = (long) tgt_prog->bpf_func;
+			else
+				addr = (long) tgt_prog->aux->func[subprog]->bpf_func;
 		} else {
 			addr = kallsyms_lookup_name(tname);
 			if (!addr) {

index 15c7378362dd..5dd37c37b29a 100644
@@ -2,25 +2,21 @@
 /* Copyright (c) 2019 Facebook */
 #include <test_progs.h>
 
-#define PROG_CNT 3
-
-void test_fexit_bpf2bpf(void)
+static void test_fexit_bpf2bpf_common(const char *obj_file,
+				      const char *target_obj_file,
+				      int prog_cnt,
+				      const char **prog_name)
 {
-	const char *prog_name[PROG_CNT] = {
-		"fexit/test_pkt_access",
-		"fexit/test_pkt_access_subprog1",
-		"fexit/test_pkt_access_subprog2",
-	};
 	struct bpf_object *obj = NULL, *pkt_obj;
 	int err, pkt_fd, i;
-	struct bpf_link *link[PROG_CNT] = {};
-	struct bpf_program *prog[PROG_CNT];
+	struct bpf_link **link = NULL;
+	struct bpf_program **prog = NULL;
 	__u32 duration, retval;
 	struct bpf_map *data_map;
 	const int zero = 0;
-	u64 result[PROG_CNT];
+	u64 *result = NULL;
 
-	err = bpf_prog_load("./test_pkt_access.o", BPF_PROG_TYPE_UNSPEC,
+	err = bpf_prog_load(target_obj_file, BPF_PROG_TYPE_UNSPEC,
 			    &pkt_obj, &pkt_fd);
 	if (CHECK(err, "prog_load sched cls", "err %d errno %d\n", err, errno))
 		return;

@@ -28,7 +24,7 @@ void test_fexit_bpf2bpf(void)
 			    .attach_prog_fd = pkt_fd,
 			   );
 
-	obj = bpf_object__open_file("./fexit_bpf2bpf.o", &opts);
+	obj = bpf_object__open_file(obj_file, &opts);
 	if (CHECK(IS_ERR_OR_NULL(obj), "obj_open",
 		  "failed to open fexit_bpf2bpf: %ld\n",
 		  PTR_ERR(obj)))

@@ -38,7 +34,14 @@ void test_fexit_bpf2bpf(void)
 	if (CHECK(err, "obj_load", "err %d\n", err))
 		goto close_prog;
 
-	for (i = 0; i < PROG_CNT; i++) {
+	link = calloc(sizeof(struct bpf_link *), prog_cnt);
+	prog = calloc(sizeof(struct bpf_program *), prog_cnt);
+	result = malloc(prog_cnt * sizeof(u64));
+	if (CHECK(!link || !prog || !result, "alloc_memory",
+		  "failed to alloc memory"))
+		goto close_prog;
+
+	for (i = 0; i < prog_cnt; i++) {
 		prog[i] = bpf_object__find_program_by_title(obj, prog_name[i]);
 		if (CHECK(!prog[i], "find_prog", "prog %s not found\n", prog_name[i]))
 			goto close_prog;

@@ -56,21 +59,54 @@ void test_fexit_bpf2bpf(void)
 	      "err %d errno %d retval %d duration %d\n",
 	      err, errno, retval, duration);
 
-	err = bpf_map_lookup_elem(bpf_map__fd(data_map), &zero, &result);
+	err = bpf_map_lookup_elem(bpf_map__fd(data_map), &zero, result);
 	if (CHECK(err, "get_result",
 		  "failed to get output data: %d\n", err))
 		goto close_prog;
 
-	for (i = 0; i < PROG_CNT; i++)
+	for (i = 0; i < prog_cnt; i++)
 		if (CHECK(result[i] != 1, "result", "fexit_bpf2bpf failed err %ld\n",
 			  result[i]))
 			goto close_prog;
 
 close_prog:
-	for (i = 0; i < PROG_CNT; i++)
+	for (i = 0; i < prog_cnt; i++)
 		if (!IS_ERR_OR_NULL(link[i]))
 			bpf_link__destroy(link[i]);
 	if (!IS_ERR_OR_NULL(obj))
 		bpf_object__close(obj);
 	bpf_object__close(pkt_obj);
+	free(link);
+	free(prog);
+	free(result);
+}
+
+static void test_target_no_callees(void)
+{
+	const char *prog_name[] = {
+		"fexit/test_pkt_md_access",
+	};
+	test_fexit_bpf2bpf_common("./fexit_bpf2bpf_simple.o",
+				  "./test_pkt_md_access.o",
+				  ARRAY_SIZE(prog_name),
+				  prog_name);
+}
+
+static void test_target_yes_callees(void)
+{
+	const char *prog_name[] = {
+		"fexit/test_pkt_access",
+		"fexit/test_pkt_access_subprog1",
+		"fexit/test_pkt_access_subprog2",
+	};
+	test_fexit_bpf2bpf_common("./fexit_bpf2bpf.o",
+				  "./test_pkt_access.o",
+				  ARRAY_SIZE(prog_name),
+				  prog_name);
+}
+
+void test_fexit_bpf2bpf(void)
+{
+	test_target_no_callees();
+	test_target_yes_callees();
 }

new file mode 100644
index 000000000000..ebc0ab7f0f5c
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook */
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+#include "bpf_trace_helpers.h"
+
+struct sk_buff {
+	unsigned int len;
+};
+
+__u64 test_result = 0;
+BPF_TRACE_2("fexit/test_pkt_md_access", test_main2,
+	    struct sk_buff *, skb, int, ret)
+{
+	int len;
+
+	__builtin_preserve_access_index(({
+		len = skb->len;
+	}));
+	if (len != 74 || ret != 0)
+		return 0;
+
+	test_result = 1;
+	return 0;
+}
+char _license[] SEC("license") = "GPL";

index 3d039e18bf82..1db2623021ad 100644
@@ -27,8 +27,8 @@ int _version SEC("version") = 1;
 	}
 #endif
 
-SEC("test1")
-int process(struct __sk_buff *skb)
+SEC("classifier/test_pkt_md_access")
+int test_pkt_md_access(struct __sk_buff *skb)
 {
 	TEST_FIELD(__u8,  len, 0xFF);
 	TEST_FIELD(__u16, len, 0xFFFF);