[PATCH 1/2] drm/amdkfd: Use mmget_not_zero in MMU notifier

[Philip Yang]

MMU notifier callback may pass in mm with mm->mm_users==0 when process
is exiting, use mmget_no_zero to avoid accessing invalid mm in deferred
list work after mm is gone.

Signed-off-by: Philip Yang <philip.y...@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 835b5187f0b8..2ba3de0fb8aa 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -2307,6 +2307,8 @@ svm_range_cpu_invalidate_pagetables(struct 
mmu_interval_notifier *mni,
 
        if (range->event == MMU_NOTIFY_RELEASE)
                return true;
+       if (!mmget_not_zero(mni->mm))
+               return true;
 
        start = mni->interval_tree.start;
        last = mni->interval_tree.last;
@@ -2333,6 +2335,7 @@ svm_range_cpu_invalidate_pagetables(struct 
mmu_interval_notifier *mni,
        }
 
        svm_range_unlock(prange);
+       mmput(mni->mm);
 
        return true;
 }
-- 
2.35.1