[PATCH] accel/qaic: Protect perf stats BO state with bo->lock

[Shuvam Pandey <shuvampandey1@gmail.com>]

qaic_perf_stats_bo_ioctl() validates each BO by checking bo->sliced and
bo->dbc before returning its perf stats. These fields are changed by the
detach paths while holding bo->lock, but the perf stats ioctl reads them
without that lock.

A concurrent detach can clear bo->dbc and mark the BO unsliced while the
perf stats ioctl is validating the BO. Take bo->lock while checking the
BO state and copying the per-BO stats into the temporary result buffer.

Fixes: 4ddf4ddfceb4 ("accel/qaic: Ensure entry belongs to DBC in qaic_perf_stats_bo_ioctl()")
Signed-off-by: Shuvam Pandey <shuvampandey1@gmail.com>
---
 drivers/accel/qaic/qaic_data.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c
index 1e4c579d2..1d74c2ec3 100644
--- a/drivers/accel/qaic/qaic_data.c
+++ b/drivers/accel/qaic/qaic_data.c
@@ -1834,15 +1834,16 @@ int qaic_perf_stats_bo_ioctl(struct drm_device *dev, void *data, struct drm_file
 			goto free_ent;
 		}
 		bo = to_qaic_bo(obj);
+		ret = mutex_lock_interruptible(&bo->lock);
+		if (ret)
+			goto put_obj;
 		if (!bo->sliced) {
-			drm_gem_object_put(obj);
 			ret = -EINVAL;
-			goto free_ent;
+			goto unlock_bo;
 		}
 		if (bo->dbc->id != args->hdr.dbc_id) {
-			drm_gem_object_put(obj);
 			ret = -EINVAL;
-			goto free_ent;
+			goto unlock_bo;
 		}
 		/*
 		 * perf stats ioctl is called before wait ioctl is complete then
@@ -1858,7 +1859,12 @@ int qaic_perf_stats_bo_ioctl(struct drm_device *dev, void *data, struct drm_file
 						    bo->perf_stats.req_received_ts), 1000);
 		ent[i].queue_level_before = bo->perf_stats.queue_level_before;
 		ent[i].num_queue_element = bo->total_slice_nents;
+unlock_bo:
+		mutex_unlock(&bo->lock);
+put_obj:
 		drm_gem_object_put(obj);
+		if (ret)
+			goto free_ent;
 	}
 
 	if (copy_to_user(u64_to_user_ptr(args->data), ent, args->hdr.count * sizeof(*ent)))
-- 
2.50.1 (Apple Git-155)