linux-kernel - Re: [PATCH] mm/mempolicy: fix potential mpol_new leak in shared_policy

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Message-ID: <0d306244-748e-9774-8578-525073770a3f@huawei.com>
Date:   Mon, 21 Mar 2022 17:25:51 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Michal Hocko <mhocko@...e.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        <kosaki.motohiro@...fujitsu.com>, <mgorman@...e.de>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/mempolicy: fix potential mpol_new leak in
 shared_policy_replace

On 2022/3/21 16:59, Michal Hocko wrote:
> On Sat 19-03-22 18:42:33, Miaohe Lin wrote:
> [...]
>> This would be triggered easily with below code snippet in my virtual machine:
>>
>> 	shmid = shmget((key_t)5566, 1024 * PAGE_SIZE, 0666|IPC_CREAT);
>> 	shm = shmat(shmid, 0, 0);
>> 	loop {
>> 		mbind(shm, 1024 * PAGE_SIZE, MPOL_LOCAL, mask, maxnode, 0);
>> 		mbind(shm + 128 * PAGE_SIZE, 128 * PAGE_SIZE, MPOL_DEFAULT, mask, maxnode, 0);
>> 	}
>>
>> If there're many process doing the above work, mpol_new will be leaked easily.
>> So should I resend this patch with Cc stable? But it seems I'am not supposed
>> to make this decision and the maintainer will take care of this?
> 
> I would just add
> Fixes: 42288fe366c4 ("mm: mempolicy: Convert shared_policy mutex to spinlock")
> Cc: stable # 3.8
> 
> And also add your above reproducer snippet added to the original changelog.
> This would be more then enough to conclude the importance.

Will do. Many thanks for your patience and suggestion!

> 
> Thank you for working hard on this!

Thanks. :)

>