On Fri, Jun 22, 2018 at 07:31:49PM -0700, Eric Biggers wrote: > On Sat, Jun 23, 2018 at 11:07:53AM +0900, Stafford Horne wrote: > > 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@xxxxxxxxxxxxxxxxxxx> > > Cc: Arnd Bergmann <arnd@xxxxxxxx> > > Signed-off-by: Stafford Horne <shorne@xxxxxxxxx> > > --- > > 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) = '/'; > > } > > It should be replaced with memcpy(), AFAICS; it wouldn't change the behavior but > it would quiet the gcc warning. Your proposed "fix" is heavily broken: notice > that the code is building a string backwards (end to beginning). Sorry about that, I didnt notice. I will fix. -Stafford
