Re: [PATCH] drm/xe: fix refcount leak in xe_range_fence_insert()

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Mon, 2026-06-08 at 06:15 +0000, Wentao Liang wrote:
> xe_range_fence_insert() acquires a reference on fence via
> dma_fence_get() and stores it in rfence->fence.  It then calls
> dma_fence_add_callback() and handles two cases: when the callback
> is successfully registered (err == 0) the fence is transferred to
> the tree for later cleanup; when the fence is already signaled
> (err == -ENOENT) it manually drops the extra reference with
> dma_fence_put(fence).
> 
> However, dma_fence_add_callback() can fail with other errors
> (e.g. -EINVAL) and in that case the code falls through to the free:
> label without releasing the acquired reference, leaking it.
> 
> Fix the leak by adding an else branch that calls dma_fence_put()
> before jumping to free: for any error other than -ENOENT.

In practice this can't happen since other errors require a missing
fence or ops.

But OTOH let's future-proof it.

> 
> Cc: stable@vger.kernel.org
> Fixes: 845f64bdbfc9 ("drm/xe: Introduce a range-fence utility")
> Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>

Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Will merge when it has passed CI.

Thanks,
Thomas


> ---
>  drivers/gpu/drm/xe/xe_range_fence.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_range_fence.c
> b/drivers/gpu/drm/xe/xe_range_fence.c
> index 372378e89e98..3d8fa194a7b0 100644
> --- a/drivers/gpu/drm/xe/xe_range_fence.c
> +++ b/drivers/gpu/drm/xe/xe_range_fence.c
> @@ -77,6 +77,8 @@ int xe_range_fence_insert(struct
> xe_range_fence_tree *tree,
>  	} else if (err == 0) {
>  		xe_range_fence_tree_insert(rfence, &tree->root);
>  		return 0;
> +	} else {
> +		dma_fence_put(fence);
>  	}
>  
>  free: