[PATCH v2 2/2] drm/xe/queue: move xa_alloc to prevent UAF

[Matthew Auld <matthew.auld@intel.com>]

Evil user can guess the next id of the queue before the ioctl completes
and then call queue destroy ioctl to trigger UAF since create ioctl is
still referencing the same queue. Move the xa_alloc all the way to the end
to prevent this.

v2:
 - Rebase

Fixes: 2149ded63079 ("drm/xe: Fix use after free when client stats are captured")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/xe/xe_exec_queue.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
index 7743ebdcbf4b..d098d2dd1b2d 100644
--- a/drivers/gpu/drm/xe/xe_exec_queue.c
+++ b/drivers/gpu/drm/xe/xe_exec_queue.c
@@ -635,12 +635,14 @@ int xe_exec_queue_create_ioctl(struct drm_device *dev, void *data,
 		}
 	}
 
+	q->xef = xe_file_get(xef);
+
+	/* user id alloc must always be last in ioctl to prevent UAF */
 	err = xa_alloc(&xef->exec_queue.xa, &id, q, xa_limit_32b, GFP_KERNEL);
 	if (err)
 		goto kill_exec_queue;
 
 	args->exec_queue_id = id;
-	q->xef = xe_file_get(xef);
 
 	return 0;
 
-- 
2.46.1