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

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Message-ID: <Yjg+hVuJBPGhkfeJ@dhcp22.suse.cz>
Date:   Mon, 21 Mar 2022 09:59:49 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Miaohe Lin <linmiaohe@...wei.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 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.

Thank you for working hard on this!
-- 
Michal Hocko
SUSE Labs