[PATCH 5.10 067/121] perf bpf: Defer freeing string after possible strlen() on it

Greg Kroah-Hartman
2022-02-21T09:18:45Z

From: Arnaldo Carvalho de Melo <acme@redhat.com>

commit 31ded1535e3182778a1d0e5c32711f55da3bc512 upstream.

This was detected by the gcc in Fedora Rawhide's gcc:

50 11.01 fedora:rawhide : FAIL gcc version 12.0.1 20220205 (Red Hat 12.0.1-0) (GCC)
inlined from 'bpf__config_obj' at util/bpf-loader.c:1242:9:
util/bpf-loader.c:1225:34: error: pointer 'map_opt' may be used after 'free' [-Werror=use-after-free]
1225 | *key_scan_pos += strlen(map_opt);
| ^~~~~~~~~~~~~~~
util/bpf-loader.c:1223:9: note: call to 'free' here
1223 | free(map_name);
| ^~~~~~~~~~~~~~
cc1: all warnings being treated as errors

So do the calculations on the pointer before freeing it.

Fixes: 04f9bf2bac72480c ("perf bpf-loader: Add missing '*' for key_scan_pos")
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang ShaoBo <bobo.shaobowang@huawei.com>
Link: https://lore.kernel.org/lkml/Yg1VtQxKrPpS3uNA@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/perf/util/bpf-loader.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -1215,9 +1215,10 @@ bpf__obj_config_map(struct bpf_object *o
pr_debug("ERROR: Invalid map config option '%s'\n", map_opt);
err = -BPF_LOADER_ERRNO__OBJCONF_MAP_OPT;
out:
- free(map_name);
if (!err)
*key_scan_pos += strlen(map_opt);
+
+ free(map_name);
return err;
}