On Mon, Jun 25, 2018 at 02:57:13PM +0200, Christophe LEROY wrote: > > > 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()' ?
Hi Christophe, Here were are writing multiple strings into a buffer from back to front. We are copying exactly strlen() bytes at a time to avoid the nul terminator being copied into the buffer. I don't doubt we could use strcpy() but I was trying to keep the change small. -Stafford > > > > Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org> > > Cc: Arnd Bergmann <a...@arndb.de> > > Cc: Eric Biggers <ebigge...@gmail.com> > > Signed-off-by: Stafford Horne <sho...@gmail.com> > > --- > > 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) = '/'; > > } > >
