[tip:perf/core] perf dso: Fix unchecked usage of strncpy()

[tip-bot for Arnaldo Carvalho de Melo]

Commit-ID:  9e107dbd15d087a4879184b5cf3deacdc2faf903
Gitweb:     https://git.kernel.org/tip/9e107dbd15d087a4879184b5cf3deacdc2faf903
Author:     Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Thu, 6 Dec 2018 10:49:46 -0300
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Thu, 6 Dec 2018 14:12:35 -0300

perf dso: Fix unchecked usage of strncpy()

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:

  In function 'decompress_kmodule',
      inlined from 'dso__decompress_kmodule_fd' at util/dso.c:305:9:
  util/dso.c:298:3: error: 'strncpy' destination unchanged after copying no bytes [-Werror=stringop-truncation]
     strncpy(pathname, tmpbuf, len);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    CC       /tmp/build/perf/util/values.o
    CC       /tmp/build/perf/util/debug.o
  cc1: all warnings being treated as errors

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Fixes: c9a8a6131fb6 ("perf tools: Move the temp file processing into decompress_kmodule")
Link: https://lkml.kernel.org/n/tip-tl2hdxj64tt4k8btbi6a0ugw@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/dso.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index bbed90e5d9bb..cee717a3794f 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -295,7 +295,7 @@ static int decompress_kmodule(struct dso *dso, const char *name,
 		unlink(tmpbuf);
 
 	if (pathname && (fd >= 0))
-		strncpy(pathname, tmpbuf, len);
+		strlcpy(pathname, tmpbuf, len);
 
 	return fd;
 }