linux-kernel - Re: [PATCH v2] 8250_lpss: check null return when calling pci_ioremap

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Message-ID: <20190726115746.GT9224@smile.fi.intel.com>
Date:   Fri, 26 Jul 2019 14:57:46 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc:     Navid Emamdoost <navid.emamdoost@...il.com>, emamd001@....edu,
        kjlu@....edu, smccaman@....edu,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Vinod Koul <vkoul@...nel.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] 8250_lpss: check null return when calling
 pci_ioremap_bar

On Fri, Jul 26, 2019 at 01:32:21PM +0200, Bartlomiej Zolnierkiewicz wrote:
> On 7/19/19 7:48 PM, Navid Emamdoost wrote:
> > pci_ioremap_bar may return null. This is eventually de-referenced at 
> > drivers/dma/dw/core.c:1154 and drivers/dma/dw/core.c:1168. A null check 
> > is needed to prevent null de-reference. I am adding the check and in case
> >  of failure. Thanks to Andy Shevchenko for the hint on the necessity of 
> > pci_iounmap when exiting.

> > @@ -169,10 +169,12 @@ static void qrk_serial_setup_dma(struct lpss8250 *lpss, struct uart_port *port)
> >  	struct pci_dev *pdev = to_pci_dev(port->dev);
> >  	int ret;
> >  
> > +	chip->pdata = &qrk_serial_dma_pdata;
> >  	chip->dev = &pdev->dev;
> >  	chip->irq = pci_irq_vector(pdev, 0);
> >  	chip->regs = pci_ioremap_bar(pdev, 1);
> > -	chip->pdata = &qrk_serial_dma_pdata;
> > +	if (!chip->regs)
> > +		return;
> >  
> >  	/* Falling back to PIO mode if DMA probing fails */
> >  	ret = dw_dma_probe(chip);
> 
> pci_iounmap() should also be called on dw_dma_probe() failure (in such
> case param->dma_dev is NULL so pci_iounmap() in qrk_serial_exit_dma()
> won't be called during exit).

Oh, yes, good catch!
Navid, can you send a follow up fix?

> > @@ -195,11 +197,15 @@ static void qrk_serial_setup_dma(struct lpss8250 *lpss, struct uart_port *port)
> >  pci_iounmap
> >  static void qrk_serial_exit_dma(struct lpss8250 *lpss)
> >  {
> > +	struct dw_dma_chip *chip = &lpss->dma_chip;
> >  	struct dw_dma_slave *param = &lpss->dma_param;
> >  
> >  	if (!param->dma_dev)
> >  		return;
> > -	dw_dma_remove(&lpss->dma_chip);
> > +
> > +	dw_dma_remove(chip);
> > +
> > +	pci_iounmap(to_pci_dev(chip->dev), chip->regs);
> >  }

-- 
With Best Regards,
Andy Shevchenko