linux-kernel - Re: [PATCH v3] PCI/sysfs: off by two when checking the limit on driver

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Date:	Tue, 24 Feb 2015 17:36:03 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Alex Williamson <alex.williamson@...hat.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Alexander Graf <agraf@...e.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v3] PCI/sysfs: off by two when checking the limit on
 driver_override length

On Wed, Feb 04, 2015 at 05:38:15PM -0500, Sasha Levin wrote:
> When printing the driver_override parameter when it is 4095 and 4094 bytes
> long the printing code would access invalid memory because we need count+1
> bytes for printing.
> 
> Cc: <stable@...r.kernel.org> # v3.16+
> Fixes: 782a985d ("PCI: Introduce new device binding path using pci_dev.driver_override")
> Cc: Alex Williamson <alex.williamson@...hat.com>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Alexander Graf <agraf@...e.de>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>

Applied with Alex's ack to for-linus for v4.0, thanks!

> ---
>  drivers/pci/pci-sysfs.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index aa012fb..312f23a 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -521,7 +521,8 @@ static ssize_t driver_override_store(struct device *dev,
>  	struct pci_dev *pdev = to_pci_dev(dev);
>  	char *driver_override, *old = pdev->driver_override, *cp;
>  
> -	if (count > PATH_MAX)
> +	/* We need to keep extra room for a newline */
> +	if (count >= (PAGE_SIZE - 1))
>  		return -EINVAL;
>  
>  	driver_override = kstrndup(buf, count, GFP_KERNEL);
> @@ -549,7 +550,7 @@ static ssize_t driver_override_show(struct device *dev,
>  {
>  	struct pci_dev *pdev = to_pci_dev(dev);
>  
> -	return sprintf(buf, "%s\n", pdev->driver_override);
> +	return snprintf(buf, PAGE_SIZE, "%s\n", pdev->driver_override);
>  }
>  static DEVICE_ATTR_RW(driver_override);
>  
> -- 
> 1.7.10.4
> 
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