[PATCH] drm/xe: Skip address copy for sync-only execs

[Shuicheng Lin <shuicheng.lin@intel.com>]

For parallel exec queues, xe_exec_ioctl() copied the batch buffer address
array from userspace without checking num_batch_buffer.
If user creates a sync-only exec that doesn't use the address field, the
exec will fail with -EFAULT.
Add num_batch_buffer check to skip the copy, and the exec could be executed
successfully.

Here is the sync-only exec:
struct drm_xe_exec exec = {
    .extensions = 0,
    .exec_queue_id = qid,
    .num_syncs = 1,
    .syncs = (uintptr_t)&sync,
    .address = 0,            /* ignored for sync-only */
    .num_batch_buffer = 0,   /* sync-only */
};

Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Cc: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>
---
 drivers/gpu/drm/xe/xe_exec.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_exec.c b/drivers/gpu/drm/xe/xe_exec.c
index a5485fe6e3f1..dbe6c006f1d6 100644
--- a/drivers/gpu/drm/xe/xe_exec.c
+++ b/drivers/gpu/drm/xe/xe_exec.c
@@ -192,9 +192,9 @@ int xe_exec_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 		goto err_syncs;
 	}
 
-	if (xe_exec_queue_is_parallel(q)) {
-		err = copy_from_user(addresses, addresses_user, sizeof(u64) *
-				     q->width);
+	if (args->num_batch_buffer && xe_exec_queue_is_parallel(q)) {
+		err = copy_from_user(addresses, addresses_user,
+				     sizeof(u64) * q->width);
 		if (err) {
 			err = -EFAULT;
 			goto err_syncs;
-- 
2.50.1