Re: [PATCH] device: fix missing check on list iterator

[Xiaomeng Tong <xiam0nd.tong@gmail.com>]

On Sat, 26 Mar 2022 22:38:05 -0700, Guenter Roeck <linux@roeck-us.net> wrote:
> > @@ -103,11 +103,16 @@ nvkm_control_mthd_pstate_attr(struct nvkm_control *ctrl, void *data, u32 size)
> >   		return -EINVAL;
> >   
> >   	if (args->v0.state != NVIF_CONTROL_PSTATE_ATTR_V0_STATE_CURRENT) {
> > -		list_for_each_entry(pstate, &clk->states, head) {
> > -			if (i++ == args->v0.state)
> > +		list_for_each_entry(iter, &clk->states, head) {
> > +			if (i++ == args->v0.state) {
> > +				pstate = iter;
> 
> Is iter and the assignment really necessary ? Unless I am missing something,
> list_for_each_entry() always assigns pos (pstate/iter), even if the list is
> empty. If nothing is found, pstate would be NULL at the end, so

the pstate will not be NULL at the end! so the assignment is necessary!
#define list_for_each_entry(pos, head, member)                          \
    for (pos = __container_of((head)->next, pos, member);               \
         &pos->member != (head);                                        \
         pos = __container_of(pos->member.next, pos, member))

--
Xiaomeng Tong