On Sat, Apr 04, 2015 at 06:20:53PM +0200, Julia Lawall wrote: > > > On Sat, 4 Apr 2015, Greg Kroah-Hartman wrote: > > > On Sat, Apr 04, 2015 at 04:59:30PM +0200, Julia Lawall wrote: > > > Put NULL test on the result of the previous call instead on one of its > > > arguments. A simplified version of the semantic match that finds this > > > problem is as follows (http://coccinelle.lip6.fr/): > > > > > > // <smpl> > > > r@ > > > expression *e1; > > > expression *e2; > > > identifier f; > > > statement S1,S2; > > > @@ > > > > > > e1 = f(...,e2,...); > > > ( > > > if (e1 == NULL || ...) S1 else S2 > > > | > > > *if (e2 == NULL || ...) S1 else S2 > > > ) > > > // </smpl> > > > > > > Signed-off-by: Julia Lawall <Julia.Lawall@xxxxxxx> > > > > > > --- > > > drivers/staging/emxx_udc/emxx_udc.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/staging/emxx_udc/emxx_udc.c b/drivers/staging/emxx_udc/emxx_udc.c > > > index fbf82bc..7de1e9e 100644 > > > --- a/drivers/staging/emxx_udc/emxx_udc.c > > > +++ b/drivers/staging/emxx_udc/emxx_udc.c > > > @@ -2998,7 +2998,7 @@ static void nbu2ss_ep_fifo_flush(struct usb_ep *_ep) > > > } > > > > > > ep = container_of(_ep, struct nbu2ss_ep, ep); > > > - if (!_ep) { > > > + if (!ep) { > > > > This is actually even worse, container_of() can't return NULL. Or if it > > does, something is really wrong (it can only happen if the field happens > > to be the first field in the structure and the original pointer was > > NULL). So I would say that all tests for container_of (and > > functions/macros that are just wrappers around container_of()) can just > > be deleted as they will never be triggered. > > Couldn't one say: > > x = NULL; > y = &x->whatever; > z = container_of(y, struct blah, whatever); > > and end up with z being NULL? Yes, if you were really lucky. If you are passing a pointer to container_of() it had better be checked to be NULL before, not after, the operation, as afterward makes no sense because this is just pointer math happening. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
