linux-kernel - Re: [PATCH v3 hmm 08/11] drm/radeon: use mmu_notifier_get/put for struct radeon

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Date:   Wed, 14 Aug 2019 13:07:46 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     linux-mm@...ck.org
Cc:     Andrea Arcangeli <aarcange@...hat.com>,
        Christoph Hellwig <hch@....de>,
        John Hubbard <jhubbard@...dia.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        "Kuehling, Felix" <Felix.Kuehling@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        Dimitri Sivanich <sivanich@....com>,
        dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        iommu@...ts.linux-foundation.org, intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH v3 hmm 08/11] drm/radeon: use mmu_notifier_get/put for
 struct radeon_mn

On Tue, Aug 06, 2019 at 08:15:45PM -0300, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@...lanox.com>
> 
> radeon is using a device global hash table to track what mmu_notifiers
> have been registered on struct mm. This is better served with the new
> get/put scheme instead.
> 
> radeon has a bug where it was not blocking notifier release() until all
> the BO's had been invalidated. This could result in a use after free of
> pages the BOs. This is tied into a second bug where radeon left the
> notifiers running endlessly even once the interval tree became
> empty. This could result in a use after free with module unload.
> 
> Both are fixed by changing the lifetime model, the BOs exist in the
> interval tree with their natural lifetimes independent of the mm_struct
> lifetime using the get/put scheme. The release runs synchronously and just
> does invalidate_start across the entire interval tree to create the
> required DMA fence.
> 
> Additions to the interval tree after release are already impossible as
> only current->mm is used during the add.
> 
> Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
>  drivers/gpu/drm/radeon/radeon.h        |   3 -
>  drivers/gpu/drm/radeon/radeon_device.c |   2 -
>  drivers/gpu/drm/radeon/radeon_drv.c    |   2 +
>  drivers/gpu/drm/radeon/radeon_mn.c     | 157 ++++++-------------------
>  4 files changed, 38 insertions(+), 126 deletions(-)

AMD team: Are you OK with this patch?

Jason