linux-kernel - Re: [PATCH 2/2] mm: set PG_dma_pinned on get_user

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Message-ID: <20180619061548.GC7557@mtr-leonro.mtl.com>
Date:   Tue, 19 Jun 2018 09:15:48 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>, john.hubbard@...il.com,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...nel.org>,
        Christopher Lameter <cl@...ux.com>, Jan Kara <jack@...e.cz>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH 2/2] mm: set PG_dma_pinned on get_user_pages*()

On Mon, Jun 18, 2018 at 10:11:13AM +0200, Christoph Hellwig wrote:
> On Sun, Jun 17, 2018 at 01:10:04PM -0700, Dan Williams wrote:
> > I believe kernel behavior regression is a primary concern as now
> > fallocate() and truncate() can randomly fail where they didn't before.
>
> Fail or block forever due to actions of other unprivileged users.
>
> That is a complete no-go.

They will fail "properly" with some error, which is better than current
situation where those unprivileged users can trigger oops.

Thanks

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