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

[Jason Gunthorpe <jgg@ziepe.ca>]

On Tue, Aug 06, 2019 at 08:15:45PM -0300, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@mellanox.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@mellanox.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
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