linux-kernel - Re: [PATCH 4.4 74/76] serial: 8250_pci: Detach low-level driver during PCI error recovery

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Date:   Tue, 04 Apr 2017 21:26:38 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Gabriel Krisman Bertazi <krisman@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Sasha Levin <alexander.levin@...izon.com>,
        Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [PATCH 4.4 74/76] serial: 8250_pci: Detach low-level driver
 during PCI error recovery

On Tue, 2017-03-28 at 14:31 +0200, Greg Kroah-Hartman wrote:
[...]
>  static void serial8250_io_resume(struct pci_dev *dev)
>  {
>  	struct serial_private *priv = pci_get_drvdata(dev);
> +	const struct pciserial_board *board;
>  
> -	if (priv)
> -		pciserial_resume_ports(priv);
> +	if (!priv)
> +		return;
> +
> +	board = priv->board;
> +	kfree(priv);
> +	priv = pciserial_init_ports(dev, board);
> +
> +	if (!IS_ERR(priv)) {
> +		pci_set_drvdata(dev, priv);
> +	}
>  }

On error, this leaves drvdata as a dangling pointer.  Removing the
device or driver will then cause a use-after-free.  (And setting drvdata
to NULL isn't enough to fix this as there is no null pointer check in
pciserial_remove_ports().)

Ben.

-- 
Ben Hutchings
Software Developer, Codethink Ltd.