Re: [PATCH] usb: gadget: aspeed_udc: check endpoint DMA allocation

Thanks! I will simplify the error path and let err_cleanup fall
through to err.

On Wed, Jun 10, 2026 at 7:45 PM Andrew Jeffery <[email protected]>
wrote:

> On Mon, 2026-06-08 at 16:19 +0800, Ruoyu Wang wrote:
> > ast_udc_probe() allocates a coherent DMA buffer used as the backing store
> > for endpoint buffers. ast_udc_init_ep() derives per-endpoint buffer
> > pointers from udc->ep0_buf, so a failed allocation is dereferenced during
> > probe.
> >
> > Check the allocation before endpoint setup. The existing probe error path
> > called ast_udc_remove(), which unregisters the gadget unconditionally and
> > is not safe before usb_add_gadget_udc() succeeds. Add a local cleanup
> > helper for probe failures so pre-registration failures only unwind the
> > resources that were actually initialized.
> >
> > This was found by a local static analysis checker for unchecked allocator
> > returns while scanning Linux 6.16. The change was checked by applying it
> > to current mainline and by running checkpatch. I do not have access to
> > Aspeed UDC hardware, so no runtime testing was performed.
> >
> > Fixes: 055276c13205 ("usb: gadget: add Aspeed ast2600 udc driver")
> > Signed-off-by: Ruoyu Wang <[email protected]>
> > ---
> > Note: a 2022 patch attempted to add only a NULL check for this
> > allocation:
> > https://lore.kernel.org/all/[email protected]/
> >
> > This version also fixes the probe unwind path so the clock is disabled
> > on allocation failure and usb_del_gadget_udc() is not called before the
> > gadget has been registered.
> >
> > diff --git a/drivers/usb/gadget/udc/aspeed_udc.c
> b/drivers/usb/gadget/udc/aspeed_udc.c
> > index 7fc6696b7..809a7d5b7 100644
> > --- a/drivers/usb/gadget/udc/aspeed_udc.c
> > +++ b/drivers/usb/gadget/udc/aspeed_udc.c
> > @@ -1434,11 +1434,34 @@ static void ast_udc_init_hw(struct ast_udc_dev
> *udc)
> >       ast_udc_write(udc, 0, AST_UDC_EP0_CTRL);
> >  }
> >
> > +static void ast_udc_cleanup(struct platform_device *pdev)
> > +{
> > +     struct ast_udc_dev *udc = platform_get_drvdata(pdev);
> > +     unsigned long flags;
> > +     u32 ctrl;
> > +
> > +     spin_lock_irqsave(&udc->lock, flags);
> > +
> > +     /* Disable upstream port connection */
> > +     ctrl = ast_udc_read(udc, AST_UDC_FUNC_CTRL) & ~USB_UPSTREAM_EN;
> > +     ast_udc_write(udc, ctrl, AST_UDC_FUNC_CTRL);
> > +
> > +     clk_disable_unprepare(udc->clk);
> > +
> > +     spin_unlock_irqrestore(&udc->lock, flags);
> > +
> > +     if (udc->ep0_buf)
> > +             dma_free_coherent(&pdev->dev,
> > +                               AST_UDC_EP_DMA_SIZE *
> AST_UDC_NUM_ENDPOINTS,
> > +                               udc->ep0_buf,
> > +                               udc->ep0_buf_dma);
> > +
> > +     udc->ep0_buf = NULL;
> > +}
> > +
> >  static void ast_udc_remove(struct platform_device *pdev)
> >  {
> >       struct ast_udc_dev *udc = platform_get_drvdata(pdev);
> > -     unsigned long flags;
> > -     u32 ctrl;
> >
> >       usb_del_gadget_udc(&udc->gadget);
> >       if (udc->driver) {
> > @@ -1453,23 +1476,7 @@ static void ast_udc_remove(struct platform_device
> *pdev)
> >               return;
> >       }
> >
> > -     spin_lock_irqsave(&udc->lock, flags);
> > -
> > -     /* Disable upstream port connection */
> > -     ctrl = ast_udc_read(udc, AST_UDC_FUNC_CTRL) & ~USB_UPSTREAM_EN;
> > -     ast_udc_write(udc, ctrl, AST_UDC_FUNC_CTRL);
> > -
> > -     clk_disable_unprepare(udc->clk);
> > -
> > -     spin_unlock_irqrestore(&udc->lock, flags);
> > -
> > -     if (udc->ep0_buf)
> > -             dma_free_coherent(&pdev->dev,
> > -                               AST_UDC_EP_DMA_SIZE *
> AST_UDC_NUM_ENDPOINTS,
> > -                               udc->ep0_buf,
> > -                               udc->ep0_buf_dma);
> > -
> > -     udc->ep0_buf = NULL;
> > +     ast_udc_cleanup(pdev);
> >  }
> >
> >  static int ast_udc_probe(struct platform_device *pdev)
> > @@ -1523,6 +1530,10 @@ static int ast_udc_probe(struct platform_device
> *pdev)
> >                                         AST_UDC_EP_DMA_SIZE *
> >                                         AST_UDC_NUM_ENDPOINTS,
> >                                         &udc->ep0_buf_dma, GFP_KERNEL);
> > +     if (!udc->ep0_buf) {
> > +             rc = -ENOMEM;
> > +             goto err_disable_clk;
> > +     }
> >
> >       udc->gadget.speed = USB_SPEED_UNKNOWN;
> >       udc->gadget.max_speed = USB_SPEED_HIGH;
> > @@ -1553,20 +1564,20 @@ static int ast_udc_probe(struct platform_device
> *pdev)
> >       udc->irq = platform_get_irq(pdev, 0);
> >       if (udc->irq < 0) {
> >               rc = udc->irq;
> > -             goto err;
> > +             goto err_cleanup;
> >       }
> >
> >       rc = devm_request_irq(&pdev->dev, udc->irq, ast_udc_isr, 0,
> >                             KBUILD_MODNAME, udc);
> >       if (rc) {
> >               dev_err(&pdev->dev, "Failed to request interrupt\n");
> > -             goto err;
> > +             goto err_cleanup;
> >       }
> >
> >       rc = usb_add_gadget_udc(&pdev->dev, &udc->gadget);
> >       if (rc) {
> >               dev_err(&pdev->dev, "Failed to add gadget udc\n");
> > -             goto err;
> > +             goto err_cleanup;
> >       }
> >
> >       dev_info(&pdev->dev, "Initialized udc in USB%s mode\n",
> > @@ -1574,9 +1585,14 @@ static int ast_udc_probe(struct platform_device
> *pdev)
> >
> >       return 0;
> >
> > +err_disable_clk:
> > +     clk_disable_unprepare(udc->clk);
> > +     goto err;
> > +err_cleanup:
> > +     ast_udc_cleanup(pdev);
> > +     goto err;
> >  err:
>
> That last goto is unnecessary.
>
> However, I find it unsettling that in a patch fixing resource handling
> we add a mildly convoluted cleanup path, with portions jumping over
> each other in this way.
>
> The err_disable_clk label is only used once, and itself jumps down to
> the err label. This is the case because beyond its goto we free udc-
> >ep0_buf in ast_udc_cleanup(). I think it would make more sense to move
> the call to clk_disable_unprepare() into the conditional body of the
> allocation failure test, then change its goto label to 'err'. That way
> the above hunk becomes:
>
>    +err_cleanup:
>    +    ast_udc_cleanup(pdev);
>     err:
>         ...
>
> Which seems a bit more natural.
>
> Andrew
>
> >       dev_err(&pdev->dev, "Failed to udc probe, rc:0x%x\n", rc);
> > -     ast_udc_remove(pdev);
> >
> >       return rc;
> >  }
>