[PATCH bpf-next v4 2/4] bpftool: btf: Validate root_type_ids early

[Daniel Xu]

Handle invalid root_type_ids early, as an invalid ID will cause dumpers
to half-emit valid boilerplate and then bail with an unclean exit. This
is ugly and possibly confusing for users, so preemptively handle the
common error case before any dumping begins.

Signed-off-by: Daniel Xu <dxu@xxxxxxxxx>
---
 tools/bpf/bpftool/btf.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index d005e4fd6128..3e995faf9efa 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -886,6 +886,7 @@ static int do_dump(int argc, char **argv)
 	const char *src;
 	int fd = -1;
 	int err = 0;
+	int i;
 
 	if (!REQ_ARGS(2)) {
 		usage();
@@ -1017,6 +1018,17 @@ static int do_dump(int argc, char **argv)
 		}
 	}
 
+	/* Invalid root IDs causes half emitted boilerplate and then unclean
+	 * exit. It's an ugly user experience, so handle common error here.
+	 */
+	for (i = 0; i < root_type_cnt; i++) {
+		if (root_type_ids[i] >= btf__type_cnt(btf)) {
+			err = -EINVAL;
+			p_err("invalid root ID: %u", root_type_ids[i]);
+			goto done;
+		}
+	}
+
 	if (dump_c) {
 		if (json_output) {
 			p_err("JSON output for C-syntax dump is not supported");
-- 
2.46.0