From: Christophe LEROY Subject: Re: [PATCH v2 2/2] kobject: Fix -Wstringop-truncation warning Date: Mon, 25 Jun 2018 14:57:13 +0200 Message-ID: References: <20180625124538.21051-1-shorne@gmail.com> <20180625124538.21051-3-shorne@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: Greg KH , arnd@arndb.de, Eric Biggers , linux-crypto@vger.kernel.org To: Stafford Horne , LKML Return-path: In-Reply-To: <20180625124538.21051-3-shorne@gmail.com> Content-Language: fr Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org Le 25/06/2018 à 14:45, Stafford Horne a écrit : > 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 not really an issue since the buffer we are writing to is > pre-zero'd and we have already allocated the buffer based on the > calculated strlen size and accounted for the terminating '\0'. > Just use memcpy() instead. If we are already sure the destination is big enough, why not just do a strcpy() and drop the 'cur = strlen()' ? Christophe > > Cc: Greg Kroah-Hartman > Cc: Arnd Bergmann > Cc: Eric Biggers > Signed-off-by: Stafford Horne > --- > lib/kobject.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/kobject.c b/lib/kobject.c > index 18989b5b3b56..e876957743c8 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); > + memcpy(path + length, kobject_name(parent), cur); > *(path + --length) = '/'; > } > >