Re: [PATCH v2] usb: dwc3: gadget: check that event count does not exceed event buffer length

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Apr 01, 2025 at 02:53:13PM +0200, Frode Isaksen wrote:
> From: Frode Isaksen <frode@meta.com>
> 
> The event count is read from register DWC3_GEVNTCOUNT.
> There is a check for the count being zero, but not for exceeding the
> event buffer length.
> Check that event count does not exceed event buffer length,
> avoiding an out-of-bounds access when memcpy'ing the event.
> Crash log:
> Unable to handle kernel paging request at virtual address ffffffc0129be000
> pc : __memcpy+0x114/0x180
> lr : dwc3_check_event_buf+0xec/0x348
> x3 : 0000000000000030 x2 : 000000000000dfc4
> x1 : ffffffc0129be000 x0 : ffffff87aad60080
> Call trace:
> __memcpy+0x114/0x180
> dwc3_interrupt+0x24/0x34
> 
> Signed-off-by: Frode Isaksen <frode@meta.com>
> Fixes: ebbb2d59398f ("usb: dwc3: gadget: use evt->cache for processing events")
> Cc: stable@vger.kernel.org
> ---
> v1->v2: added error log
> 
>  drivers/usb/dwc3/gadget.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 89a4dc8ebf94..923737776d82 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -4564,6 +4564,12 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt)
>  	if (!count)
>  		return IRQ_NONE;
>  
> +	if (count > evt->length) {
> +		dev_err(dwc->dev, "invalid count(%u) > evt->length(%u)\n",
> +			count, evt->length);

Is this wise to do in an irq handler?  If the hardware goes crazy, will
this just fill the logs?  Why not rate-limit it?

thanks,

greg k-h