bpftool: btf: Validate root_type_ids early

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@dxuuu.xyz>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/bpf/33e09a08a6072f8381cb976218a009709309b7e1.1734119028.git.dxu@dxuuu.xyz

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index d005e4fd6128a230a6fda7d7920e3b2629db2781..3e995faf9efa630aa19afe07de2021bef081d753 100644 (file)
--- 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");