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Subject: Re: [PATCH] mm: cma: fix corruption cma_sysfs_alloc_pages_count
To:     Minchan Kim <minchan@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>, gregkh@linuxfoundation.org,
        surenb@google.com, joaodias@google.com, jhubbard@nvidia.com,
        willy@infradead.org
References: <20210324192044.1505747-1-minchan@kernel.org>
 <18ee5c3e-fba2-0d8d-bd93-5fb8d0dd7a01@gmail.com>
 <89ba4c7a-42d2-5412-2367-cc1cffc1117b@gmail.com>
 <YFuZua1TIEkXtqoL@google.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <900f5707-3352-e3d1-69e8-c1f8580c0fc4@gmail.com>
Date:   Wed, 24 Mar 2021 23:02:47 +0300
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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.