linux-kernel - Re: [PATCH RFC v2 4/4] mm/mempolicy: add nodes_empty check in SYSC_migrate

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Message-ID: <alpine.DEB.2.20.1711060926001.9015@nuc-kabylake>
Date:   Mon, 6 Nov 2017 09:29:49 -0600 (CST)
From:   Christopher Lameter <cl@...ux.com>
To:     Vlastimil Babka <vbabka@...e.cz>
cc:     Yisheng Xie <xieyisheng1@...wei.com>, akpm@...ux-foundation.org,
        mhocko@...e.com, mingo@...nel.org, rientjes@...gle.com,
        n-horiguchi@...jp.nec.com, salls@...ucsb.edu, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, tanxiaojun@...wei.com,
        linux-api@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH RFC v2 4/4] mm/mempolicy: add nodes_empty check in
 SYSC_migrate_pages

On Mon, 6 Nov 2017, Vlastimil Babka wrote:

> I'm not sure what exactly is the EPERM intention. Should really the
> capability of THIS process override the cpuset restriction of the TARGET
> process? Maybe yes. Then, does "insufficient privilege (CAP_SYS_NICE) to

CAP_SYS_NICE never overrides cpuset restrictions. The cap can be used to
migrate pages that are *also* mapped by other processes (and thus move
pages of another process which may have different cpu set restrictions!).
The cap should not allow migrating pages to nodes that are not allowed by
the cpuset of the current process.