[PATCH 5.15 008/106] drm/amdkfd: Use mmget_not_zero in MMU notifier

[Greg Kroah-Hartman]

From: Philip Yang <Philip.Yang@xxxxxxx>

[ Upstream commit fa582c6f3684ac0098a9d02ddf0ed52a02b37127 ]

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@xxxxxxx>
Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 830809b694dd..74e6f613be02 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
@@ -2181,6 +2181,8 @@ 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;
@@ -2207,6 +2209,7 @@ svm_range_cpu_invalidate_pagetables(struct mmu_interval_notifier *mni,
 	}
 
 	svm_range_unlock(prange);
+	mmput(mni->mm);
 
 	return true;
 }
-- 
2.35.1