Re: [PATCH] mm: cma: fix corruption cma_sysfs_alloc_pages_count

Minchan Kim
2021-03-24T20:57:11Z

On Wed, Mar 24, 2021 at 11:02:47PM +0300, Dmitry Osipenko wrote:
> 24.03.2021 22:57, Minchan Kim пишет:
> > On Wed, Mar 24, 2021 at 10:49:58PM +0300, Dmitry Osipenko wrote:
> >> 24.03.2021 22:43, Dmitry Osipenko пишет:
> >>> 24.03.2021 22:20, Minchan Kim пишет:
> >>>> static int __init cma_sysfs_init(void)
> >>>> {
> >>>> - int i = 0;
> >>>> + struct kobject *cma_kobj_root;
> >>>> + struct cma_kobject *cma_kobj;
> >>>> struct cma *cma;
> >>>> + unsigned int i;
> >>>
> >>>> while (--i >= 0) {
> >>>
> >>> Do you realize that this doesn't work anymore?
> >>>
> >>>> cma = &cma_areas[i];
> >>>> - kobject_put(&cma->stat->kobj);
> >>>> - }
> >>>>
> >>>> - kfree(cma_stats);
> >>>> - kobject_put(cma_kobj);
> >>>> + kobject_put(&cma->cma_kobj->kobj);
> >>>> + kfree(cma->cma_kobj);
> >>>
> >>> Freeing a null pointer?
> >>>
> >>>> + cma->cma_kobj = NULL;
> >>>> + }
> >>>> + kobject_put(cma_kobj_root);
> >>>
> >>
> >> Please try to simulate the errors and check that error path is working
> >> properly in the next version.
> >>
> >> Alternatively, we could remove the cma_kobj_release entirely, like Greg
> >> suggested previously, and then don't care about cleaning up at all.
> >
> > Does he suggested it to remove cma_kobj_release?(Initially, I did but
> > was rejected from Greg)
> >
>
> Alright, I haven't followed the previous threads fully and only saw the
> reply where he suggested to removed it.

No problem. I just posted it new version. Hopefully, it tastes good
for you. ;-)

Thanks for the review!