perf header: Fix unchecked usage of strncpy()

[ Upstream commit 7572588085a13d5db02bf159542189f52fdb507e ]

The strncpy() function may leave the destination string buffer
unterminated, better use strlcpy() that we have a __weak fallback
implementation for systems without it.

This fixes this warning on an Alpine Linux Edge system with gcc 8.2:

  util/header.c: In function 'perf_event__synthesize_event_update_unit':
  util/header.c:3586:2: error: 'strncpy' output truncated before terminating nul copying as many bytes from a string as its length [-Werror=stringop-truncation]
    strncpy(ev->data, evsel->unit, size);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  util/header.c:3579:16: note: length computed here
    size_t size = strlen(evsel->unit);
                  ^~~~~~~~~~~~~~~~~~~

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Fixes: a6e5281780d1 ("perf tools: Add event_update event unit type")
Link: https://lkml.kernel.org/n/tip-fiikh5nay70bv4zskw2aa858@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 1ceb332575bd12a798665538a7c00884d8901af0..696f2654826bf6cae8ca5d576d175debcfb23724 100644 (file)
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3132,7 +3132,7 @@ perf_event__synthesize_event_update_unit(struct perf_tool *tool,
        if (ev == NULL)
                return -ENOMEM;
 
-       strncpy(ev->data, evsel->unit, size);
+       strlcpy(ev->data, evsel->unit, size + 1);
        err = process(tool, (union perf_event *)ev, NULL, NULL);
        free(ev);
        return err;