Re: [PATCH v2] usb: chipidea: host: Improve port index sanitizing

[Peter Chen <peter.chen@kernel.org>]

On 24-12-02 16:34:53, Xu Yang wrote:
> Coverity from Synopsys complains "Illegal address computation (OVERRUN)"
> on status_reg.
> 
> After below code executed,
> 
>   port_index = wIndex & 0xff;
>   port_index -= (port_index > 0);
> 
> the static analysis tool see the value of port_index is now between 0 and
> 254 (inclusive).
> 
> However, ehci_def.h define port_status as below:
> 
>   #define HCS_N_PORTS_MAX         15
>   u32     port_status[HCS_N_PORTS_MAX];
> 
> So the tool think illegal array pointer may be obtained.
> 
>   status_reg = &ehci->regs->port_status[port_index];
> 
> This will follow "846cbf98cbef USB: EHCI: Improve port index sanitizing" to
> improve port index sanitizing.
> 
> Signed-off-by: Xu Yang <xu.yang_2@nxp.com>

Acked-by: Peter Chen <peter.chen@kernel.org>

Peter
> 
> ---
> Changes in v2:
>  - rewrite commit message to better understand the issue
> ---
>  drivers/usb/chipidea/host.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/chipidea/host.c b/drivers/usb/chipidea/host.c
> index 0cce19208370..442d79e32a65 100644
> --- a/drivers/usb/chipidea/host.c
> +++ b/drivers/usb/chipidea/host.c
> @@ -256,8 +256,14 @@ static int ci_ehci_hub_control(
>  	struct device *dev = hcd->self.controller;
>  	struct ci_hdrc *ci = dev_get_drvdata(dev);
>  
> -	port_index = wIndex & 0xff;
> -	port_index -= (port_index > 0);
> +	/*
> +	 * Avoid out-of-bounds values while calculating the port index
> +	 * from wIndex. The compiler doesn't like pointers to invalid
> +	 * addresses, even if they are never used.
> +	 */
> +	port_index = (wIndex - 1) & 0xff;
> +	if (port_index >= HCS_N_PORTS_MAX)
> +		port_index = 0;
>  	status_reg = &ehci->regs->port_status[port_index];
>  
>  	spin_lock_irqsave(&ehci->lock, flags);
> -- 
> 2.34.1
>