Re: [PATCH 11/24] serial: 8250: cap OxSemi Tornado UART count against BAR size

[Ilpo Järvinen]

On Tue, 27 Oct 2026, Greg Kroah-Hartman wrote:

> From: Joshua Rogers <linux@xxxxxxxxx>
> 
> pci_oxsemi_tornado_init() reads the UART count from device-controlled
> BAR0 memory without validation, allowing a malicious device to report up
> to 255 ports. Cap the device-reported count against what actually fits
> in the BAR using the Tornado register layout.
> 
> Cc: Jiri Slaby <jirislaby@xxxxxxxxxx>
> Cc: "Uwe Kleine-König (The Capable Hub)" <u.kleine-koenig@xxxxxxxxxxxx>
> Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Cc: Lukas Wunner <lukas@xxxxxxxxx>
> Cc: Marnix Rijnart <marnix.rijnart@xxxxxxxx>
> Cc: Crescent Hsieh <crescentcy.hsieh@xxxxxxxx>
> Cc: stable <stable@xxxxxxxxxx>
> Signed-off-by: Joshua Rogers <linux@xxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
>  drivers/tty/serial/8250/8250_pci.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
> index 1dda63be6b89..9919504334bb 100644
> --- a/drivers/tty/serial/8250/8250_pci.c
> +++ b/drivers/tty/serial/8250/8250_pci.c
> @@ -1083,6 +1083,7 @@ static int pci_oxsemi_tornado_init(struct pci_dev *dev)
>  	u8 __iomem *p;
>  	unsigned long deviceID;
>  	unsigned int  number_uarts = 0;
> +	resource_size_t bar_len;
>  
>  	if (!pci_oxsemi_tornado_p(dev))
>  		return 0;
> @@ -1095,6 +1096,15 @@ static int pci_oxsemi_tornado_init(struct pci_dev *dev)
>  	/* Tornado device */
>  	if (deviceID == 0x07000200) {
>  		number_uarts = ioread8(p + 4);
> +
> +		/* Cap against BAR0 size (Tornado layout: 0x1000 + n * 0x200) */
> +		bar_len = pci_resource_len(dev, 0);
> +		if (bar_len >= 0x1000)
> +			number_uarts = min_t(unsigned int, number_uarts,
> +					     (bar_len - 0x1000) / 0x200);

IMO, these literals would be better written as SZ_xx + make sure you've 
the include for it if changing to that.

> +		else
> +			number_uarts = 0;
> +
>  		pci_dbg(dev, "%d ports detected on %s PCI Express device\n",
>  			number_uarts,
>  			dev->vendor == PCI_VENDOR_ID_ENDRUN ?
> 
> 

-- 
 i.