linux-kernel - [RFC PATCH 2/2] kobject: Fix -Wstringop-truncation warning

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 23 Jun 2018 11:07:53 +0900
From:   Stafford Horne <shorne@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>, arnd@...db.de,
        linux-crypto@...r.kernel.org, Stafford Horne <shorne@...il.com>
Subject: [RFC PATCH 2/2] kobject: Fix -Wstringop-truncation warning

When compiling with GCC 9.0.0 I am seeing the following warning:

    In function ‘fill_kobj_path’,
	inlined from ‘kobject_get_path’ at lib/kobject.c:155:2:
    lib/kobject.c:128:3: warning: ‘strncpy’ output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
       strncpy(path + length, kobject_name(parent), cur);
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    lib/kobject.c: In function ‘kobject_get_path’:
    lib/kobject.c:125:13: note: length computed here
       int cur = strlen(kobject_name(parent));
		 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is pointing out a bug that the strncpy limit is the source string not the
destination buffer remaining length.  Fix it.

Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Stafford Horne <shorne@...il.com>
---
 lib/kobject.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/kobject.c b/lib/kobject.c
index 18989b5b3b56..15338e5a96f2 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -125,7 +125,7 @@ static void fill_kobj_path(struct kobject *kobj, char *path, int length)
 		int cur = strlen(kobject_name(parent));
 		/* back up enough to print this name with '/' */
 		length -= cur;
-		strncpy(path + length, kobject_name(parent), cur);
+		strncpy(path + length, kobject_name(parent), length);
 		*(path + --length) = '/';
 	}
 
-- 
2.17.0