perf bpf-event: Fix use-after-free in synthesis

Calls to perf_env__insert_bpf_prog_info may fail as a sideband thread
may already have inserted the bpf_prog_info. Such failures may yield
info_linear being freed which then causes use-after-free issues with
the internal bpf_prog_info info struct. Make it so that
perf_env__insert_bpf_prog_info trigger early non-error paths and fix
the use-after-free in perf_event__synthesize_one_bpf_prog. Add proper
return error handling to perf_env__add_bpf_info (that calls
perf_env__insert_bpf_prog_info) and propagate the return value in its
callers.

Closes: https://lore.kernel.org/lkml/CAP-5=[e-mail]/
Fixes: 03edb7020bb9 ("perf bpf: Fix two memory leakages when calling perf_env__insert_bpf_prog_info()")
Reviewed-by: Namhyung Kim <[e-mail]>
Signed-off-by: Ian Rogers <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Namhyung Kim <[e-mail]>

tools/perf/util/bpf-event.c

···
 		info_node->info_linear = info_linear;
 		info_node->metadata = NULL;
 		if (!perf_env__insert_bpf_prog_info(env, info_node)) {
-			free(info_linear);
+			/*
+			 * Insert failed, likely because of a duplicate event
+			 * made by the sideband thread. Ignore synthesizing the
+			 * metadata.
+			 */
 			free(info_node);
+			goto out;
 		}
+		/* info_linear is now owned by info_node and shouldn't be freed below. */
 		info_linear = NULL;
 
 		/*
···
 	return err;
 }
 
-static void perf_env__add_bpf_info(struct perf_env *env, u32 id)
+static int perf_env__add_bpf_info(struct perf_env *env, u32 id)
 {
 	struct bpf_prog_info_node *info_node;
 	struct perf_bpil *info_linear;
 	struct btf *btf = NULL;
 	u64 arrays;
 	u32 btf_id;
-	int fd;
+	int fd, err = 0;
 
 	fd = bpf_prog_get_fd_by_id(id);
 	if (fd < 0)
-		return;
+		return -EINVAL;
 
 	arrays = 1UL << PERF_BPIL_JITED_KSYMS;
 	arrays |= 1UL << PERF_BPIL_JITED_FUNC_LENS;
···
 	info_linear = get_bpf_prog_info_linear(fd, arrays);
 	if (IS_ERR_OR_NULL(info_linear)) {
 		pr_debug("%s: failed to get BPF program info. aborting\n", __func__);
+		err = PTR_ERR(info_linear);
 		goto out;
 	}
 
···
 		info_node->info_linear = info_linear;
 		info_node->metadata = bpf_metadata_create(&info_linear->info);
 		if (!perf_env__insert_bpf_prog_info(env, info_node)) {
+			pr_debug("%s: duplicate add bpf info request for id %u\n",
+				 __func__, btf_id);
 			free(info_linear);
 			free(info_node);
+			goto out;
 		}
-	} else
+	} else {
 		free(info_linear);
+		err = -ENOMEM;
+		goto out;
+	}
 
 	if (btf_id == 0)
 		goto out;
 
 	btf = btf__load_from_kernel_by_id(btf_id);
-	if (libbpf_get_error(btf)) {
-		pr_debug("%s: failed to get BTF of id %u, aborting\n",
-			 __func__, btf_id);
-		goto out;
+	if (!btf) {
+		err = -errno;
+		pr_debug("%s: failed to get BTF of id %u %d\n", __func__, btf_id, err);
+	} else {
+		perf_env__fetch_btf(env, btf_id, btf);
 	}
-	perf_env__fetch_btf(env, btf_id, btf);
 
 out:
 	btf__free(btf);
 	close(fd);
+	return err;
 }
 
 static int bpf_event__sb_cb(union perf_event *event, void *data)
 {
 	struct perf_env *env = data;
+	int ret = 0;
 
 	if (event->header.type != PERF_RECORD_BPF_EVENT)
 		return -1;
 
 	switch (event->bpf.type) {
 	case PERF_BPF_EVENT_PROG_LOAD:
-		perf_env__add_bpf_info(env, event->bpf.id);
+		ret = perf_env__add_bpf_info(env, event->bpf.id);
 
 	case PERF_BPF_EVENT_PROG_UNLOAD:
 		/*
···
 		break;
 	}
 
-	return 0;
+	return ret;
 }
 
 int evlist__add_bpf_sb_event(struct evlist *evlist, struct perf_env *env)