Re: [PATCH 1/1] drm/xe: Fix error cleanup in xe_exec_queue_create_ioctl()

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Apr 08, 2026 at 02:06:47AM +0000, Shuicheng Lin wrote:
> Two error handling issues exist in xe_exec_queue_create_ioctl():
> 
> 1. When xe_hw_engine_group_add_exec_queue() fails, the error path jumps
>    to put_exec_queue which skips xe_exec_queue_kill(). If the VM is in
>    preempt fence mode, xe_vm_add_compute_exec_queue() has already added
>    the queue to the VM's compute exec queue list. Skipping the kill
>    leaves the queue on that list, leading to a dangling pointer after
>    the queue is freed.
> 
> 2. When xa_alloc() fails after xe_hw_engine_group_add_exec_queue() has
>    succeeded, the error path does not call
>    xe_hw_engine_group_del_exec_queue() to remove the queue from the hw
>    engine group list. The queue is then freed while still linked into
>    the hw engine group, causing a use-after-free.
> 
> Fix both by:
> - Changing the xe_hw_engine_group_add_exec_queue() failure path to jump
>   to kill_exec_queue so that xe_exec_queue_kill() properly removes the
>   queue from the VM's compute list.
> - Adding a del_hw_engine_group label before kill_exec_queue for the
>   xa_alloc() failure path, which removes the queue from the hw engine
>   group before proceeding with the rest of the cleanup.
> 
> Fixes: 7970cb36966c ("'drm/xe/hw_engine_group: Register hw engine group's exec queues")
> Cc: Francois Dugast <francois.dugast@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> Cc: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
> Assisted-by: Claude:claude-opus-4.6
> Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>
> ---
> This is a reimplementation of https://patchwork.freedesktop.org/series/162714/
> Same logic, with improved labeling and a corrected Fixes tag.
> ---
>  drivers/gpu/drm/xe/xe_exec_queue.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_exec_queue.c b/drivers/gpu/drm/xe/xe_exec_queue.c
> index b287d0e0e60a..4603ff08d860 100644
> --- a/drivers/gpu/drm/xe/xe_exec_queue.c
> +++ b/drivers/gpu/drm/xe/xe_exec_queue.c
> @@ -1405,7 +1405,7 @@ int xe_exec_queue_create_ioctl(struct drm_device *dev, void *data,
>  		if (q->vm && q->hwe->hw_engine_group) {
>  			err = xe_hw_engine_group_add_exec_queue(q->hwe->hw_engine_group, q);
>  			if (err)
> -				goto put_exec_queue;
> +				goto kill_exec_queue;
>  		}
>  	}
>  
> @@ -1416,12 +1416,15 @@ int xe_exec_queue_create_ioctl(struct drm_device *dev, void *data,
>  	/* 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;
> +		goto del_hw_engine_group;
>  
>  	args->exec_queue_id = id;
>  
>  	return 0;
>  
> +del_hw_engine_group:
> +	if (q->vm && q->hwe && q->hwe->hw_engine_group)
> +		xe_hw_engine_group_del_exec_queue(q->hwe->hw_engine_group, q);
>  kill_exec_queue:
>  	xe_exec_queue_kill(q);
>  delete_queue_group:
> -- 
> 2.43.0
>