Hi Andrew,
On Mon, Jun 30, 2014 at 06:57:48PM +0000, Lewycky, Andrew wrote:
> As an aside we found another small issue: amd_iommu_bind_pasid calls
> get_task_mm. This bumps the mm_struct use count and it will never be
> released. This would prevent the buggy code path described above from
> ever running in the first place.
You are right, the current code is a bit problematic, but to fix this no
new notifier chain in mm-code is needed.
In fact, using get_task_mm() is a good way to keep a reference to the mm
as a user (an external device is in fact another user) and defer the
destruction of the mappings to the file-close path (where you can call
mmput to destroy it). So this is another way to solve the problem
without any new notifier.
Joerg
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