perf probe: Fix unchecked usage of strncpy()

[ Upstream commit bef0b8970f27da5ca223e522a174d03e2587761d ]

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

In this case the 'target' buffer is coming from a list of build-ids that
are expected to have a len of at most (SBUILD_ID_SIZE - 1) chars, so
probably we're safe, but since we're using strncpy() here, use strlcpy()
instead to provide the intended safety checking without the using the
problematic strncpy() function.

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

  util/probe-file.c: In function 'probe_cache__open.isra.5':
  util/probe-file.c:427:3: error: 'strncpy' specified bound 41 equals destination size [-Werror=stringop-truncation]
     strncpy(sbuildid, target, SBUILD_ID_SIZE);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  cc1: all warnings being treated as errors

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Fixes: 1f3736c9c833 ("perf probe: Show all cached probes")
Link: https://lkml.kernel.org/n/tip-l7n8ggc9kl38qtdlouke5yp5@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/probe-file.c b/tools/perf/util/probe-file.c
index cdf8d83a484c1408608c78cace95da4e29b0c242..6ab9230ce8ee0839135e235e3d714e48d3f90d13 100644 (file)
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -424,7 +424,7 @@ static int probe_cache__open(struct probe_cache *pcache, const char *target,
 
        if (target && build_id_cache__cached(target)) {
                /* This is a cached buildid */
-               strncpy(sbuildid, target, SBUILD_ID_SIZE);
+               strlcpy(sbuildid, target, SBUILD_ID_SIZE);
                dir_name = build_id_cache__linkname(sbuildid, NULL, 0);
                goto found;
        }