From 9b85c2d4508563f4bb1de0d971ed02fea0d0d757 Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Tue, 28 Nov 2017 17:44:28 -0800 Subject: [PATCH] tools: bpftool: fix crash on bad parameters with JSON If bad or unrecognised parameters are specified after JSON output is requested, `usage()` will try to output null JSON object before the writer is created. To prevent this, create the writer as soon as the `--json` option is parsed. Fixes: 004b45c0e51a ("tools: bpftool: provide JSON output for all possible commands") Reported-by: Jakub Kicinski Signed-off-by: Quentin Monnet Acked-by: Jakub Kicinski Signed-off-by: Daniel Borkmann --- tools/bpf/bpftool/main.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c index d6e4762170a4..14ad54a1c404 100644 --- a/tools/bpf/bpftool/main.c +++ b/tools/bpf/bpftool/main.c @@ -291,7 +291,15 @@ int main(int argc, char **argv) pretty_output = true; /* fall through */ case 'j': - json_output = true; + if (!json_output) { + json_wtr = jsonw_new(stdout); + if (!json_wtr) { + p_err("failed to create JSON writer"); + return -1; + } + json_output = true; + } + jsonw_pretty(json_wtr, pretty_output); break; case 'f': show_pinned = true; @@ -306,15 +314,6 @@ int main(int argc, char **argv) if (argc < 0) usage(); - if (json_output) { - json_wtr = jsonw_new(stdout); - if (!json_wtr) { - p_err("failed to create JSON writer"); - return -1; - } - jsonw_pretty(json_wtr, pretty_output); - } - bfd_init(); ret = cmd_select(cmds, argc, argv, do_help);