linux-kernel - Re: [PATCH] mm: cma: fix corruption cma_sysfs_alloc_pages

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Date:   Wed, 24 Mar 2021 12:57:45 -0700
From:   Minchan Kim <minchan@...nel.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, gregkh@...uxfoundation.org,
        surenb@...gle.com, joaodias@...gle.com, jhubbard@...dia.com,
        willy@...radead.org
Subject: Re: [PATCH] mm: cma: fix corruption cma_sysfs_alloc_pages_count

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)