drm/amdkfd: Use mmget_not_zero in MMU notifier

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.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
index 2ebf0132c25bfb822f5d2c36e43e2bc61e3e917b..3bd0f1a670bb71e1d6a52024a1b1168900820a1e 100644 (file)
--- 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;
 }