linux-kernel - [PATCH] tools/lib/api/fs/fs.c: Fix misuse of strncpy()

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Message-ID: <20180721021026.GQ14131@decadent.org.uk>
Date:   Sat, 21 Jul 2018 03:10:26 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] tools/lib/api/fs/fs.c: Fix misuse of strncpy()

gcc 8 reports:

In function 'fs__env_override',
    inlined from 'fs__get_mountpoint' at fs/fs.c:228:6:
fs/fs.c:222:2: error: 'strncpy' specified bound 4096 equals destination size [-Werror=stringop-truncation]
  strncpy(fs->path, override_path, sizeof(fs->path));
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I'm not convinced it makes sense to truncate the copied string here,
but since we're already doing so let's ensure it's still null-
terminated.  Use strlcpy() instead.

Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Cc: stable@...r.kernel.org
---
 tools/lib/api/fs/fs.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -12,6 +12,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <sys/mount.h>
+#include <linux/string.h>
 
 #include "fs.h"
 #include "debug-internal.h"
@@ -219,7 +220,7 @@ static bool fs__env_override(struct fs *
 		return false;
 
 	fs->found = true;
-	strncpy(fs->path, override_path, sizeof(fs->path));
+	strlcpy(fs->path, override_path, sizeof(fs->path));
 	return true;
 }
 

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