[PATCH 4.9 039/102] perf header: Fix unchecked usage of strncpy()

[Greg Kroah-Hartman]

From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

commit 5192bde7d98c99f2cd80225649e3c2e7493722f7 upstream.

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_name':
  util/header.c:3625:2: error: 'strncpy' output truncated before terminating nul copying as many bytes from a string as its length [-Werror=stringop-truncation]
    strncpy(ev->data, evsel->name, len);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  util/header.c:3618:15: note: length computed here
    size_t len = strlen(evsel->name);
                 ^~~~~~~~~~~~~~~~~~~

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Fixes: a6e5281780d1 ("perf tools: Add event_update event unit type")
Link: https://lkml.kernel.org/n/tip-wycz66iy8dl2z3yifgqf894p@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 tools/perf/util/header.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3027,7 +3027,7 @@ perf_event__synthesize_event_update_name
 	if (ev == NULL)
 		return -ENOMEM;
 
-	strncpy(ev->data, evsel->name, len);
+	strlcpy(ev->data, evsel->name, len + 1);
 	err = process(tool, (union perf_event*) ev, NULL, NULL);
 	free(ev);
 	return err;