linux-kernel - [PATCH 66/75] perf probe: Fix unchecked usage of strncpy()

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Message-Id: <20181206212602.20474-67-acme@kernel.org>
Date:   Thu,  6 Dec 2018 18:25:53 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Clark Williams <williams@...hat.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH 66/75] perf probe: Fix unchecked usage of strncpy()

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

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@...el.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.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@...hat.com>
---
 tools/perf/util/probe-file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index aac7817d9e14..0b1195cad0e5 100644
--- 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;
 	}
-- 
2.19.2