On Wed, Apr 29, 2020 at 08:44:21AM -0700, Paul E. McKenney wrote:
> On Wed, Apr 29, 2020 at 04:24:02PM +0300, Dan Carpenter wrote:
> > Hello Paul E. McKenney,
> >
> > The patch e02882cd57e3: "rcutorture: Add races with task-exit
> > processing" from Apr 24, 2020, leads to the following static checker
> > warning:
> >
> > kernel/rcu/rcutorture.c:2429 rcu_torture_read_exit()
> > warn: 'rep' was already freed.
>
> Ah, good catch, will fix!
>
> > kernel/rcu/rcutorture.c
> > 2369 static int rcu_torture_read_exit(void *unused)
> > 2370 {
> > 2371 int count = 0;
> > 2372 bool errexit = false;
> > 2373 int i;
> > 2374 struct task_struct **rep;
> > 2375 struct torture_random_state *trsp;
> > 2376
> > 2377 // Allocate and initialize.
> > 2378 set_user_nice(current, MAX_NICE);
> > 2379 rep = kcalloc(read_exit, sizeof(*rep), GFP_KERNEL);
> > 2380 trsp = kcalloc(read_exit, sizeof(*trsp), GFP_KERNEL);
> > 2381 if (rep && trsp) {
> > 2382 for (i = 0; i < read_exit; i++)
> > 2383 torture_random_init(&trsp[i]);
> > 2384 VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of test");
> > 2385 } else {
> > 2386 kfree(rep);
> > ^^^
> > 2387 kfree(trsp);
> > ^^^^
> > Freed.
>
> And setting both rep and trsp to NULL here takes care of this, correct?
> As in kfree(NULL) is a no-op. Or is your tool more strict?
Yes, yes. Setting it to NULL works. I thought about that, or returning
and I wasn't sure which was prefered.
regards,
dan carpenter
