[PATCH v2] drm/imagination: acquire vm_ctx->lock before mapping memory to GPU VM

[Icenowy Zheng <zhengxingda@iscas.ac.cn>]

The drm gpuvm code doesn't protect find operation against map operation,
and the driver needs to ensure a map operation shouldn't happen when a
find operation is in progress.

As all occurences of drm_gpuva_find*() is already guarded by
vm_ctx->lock, make pvr_vm_map() to acquire this lock to prevent
disturbing any find operation.

This fixes occasional NULL deference in drm_gpuva_find*().

Cc: stable@vger.kernel.org
Fixes: 4bc736f890ce ("drm/imagination: vm: make use of GPUVM's drm_exec helper")
Signed-off-by: Icenowy Zheng <zhengxingda@iscas.ac.cn>
---
Changes in v2:
- Fixed wrong commit prefix.

 drivers/gpu/drm/imagination/pvr_vm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/imagination/pvr_vm.c b/drivers/gpu/drm/imagination/pvr_vm.c
index e1ec60f34b6e6..eea88e7ad03c1 100644
--- a/drivers/gpu/drm/imagination/pvr_vm.c
+++ b/drivers/gpu/drm/imagination/pvr_vm.c
@@ -747,6 +747,7 @@ pvr_vm_map(struct pvr_vm_context *vm_ctx, struct pvr_gem_object *pvr_obj,
 
 	pvr_gem_object_get(pvr_obj);
 
+	mutex_lock(&vm_ctx->lock);
 	err = drm_gpuvm_exec_lock(&vm_exec);
 	if (err)
 		goto err_cleanup;
@@ -754,9 +755,11 @@ pvr_vm_map(struct pvr_vm_context *vm_ctx, struct pvr_gem_object *pvr_obj,
 	err = pvr_vm_bind_op_exec(&bind_op);
 
 	drm_gpuvm_exec_unlock(&vm_exec);
+	mutex_unlock(&vm_ctx->lock);
 
 err_cleanup:
 	pvr_vm_bind_op_fini(&bind_op);
+	mutex_unlock(&vm_ctx->lock);
 
 	return err;
 }
-- 
2.52.0