[PATCH 12/62] drm/gpusvm.c: Fix a locking bug in an error path

[Bart Van Assche <bvanassche@acm.org>]

Only call drm_gpusvm_notifier_unlock() if drm_gpusvm_notifier_lock() was
called first. This has been detected by the Clang thread-safety
analyzer. Compile-tested only.

Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Fixes: f1d08a586482 ("drm/gpusvm: Introduce a function to scan the current migration state")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/gpu/drm/drm_gpusvm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index 24180bfdf5a2..e9b79ab2f83c 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -819,7 +819,7 @@ enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,
 
 		if (!(pfns[i] & HMM_PFN_VALID)) {
 			state = DRM_GPUSVM_SCAN_UNPOPULATED;
-			goto err_free;
+			goto unlock;
 		}
 
 		page = hmm_pfn_to_page(pfns[i]);
@@ -856,9 +856,10 @@ enum drm_gpusvm_scan_result drm_gpusvm_scan_mm(struct drm_gpusvm_range *range,
 		i += 1ul << drm_gpusvm_hmm_pfn_to_order(pfns[i], i, npages);
 	}
 
-err_free:
+unlock:
 	drm_gpusvm_notifier_unlock(range->gpusvm);
 
+err_free:
 	kvfree(pfns);
 	return state;
 }