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). - Eric
