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

[Krishna Kurapati <krishna.kurapati@oss.qualcomm.com>]

On 3/28/2025 4:14 PM, 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 Fixes and Cc tag.
> 
> This bug was discovered, tested and fixed (no more crashes seen) on Meta Quest 3 device.
> Also tested on T.I. AM62x board.
> 
>   drivers/usb/dwc3/gadget.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 63fef4a1a498..548e112167f3 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -4564,7 +4564,7 @@ static irqreturn_t dwc3_check_event_buf(struct dwc3_event_buffer *evt)
>   
>   	count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
>   	count &= DWC3_GEVNTCOUNT_MASK;
> -	if (!count)
> +	if (!count || count > evt->length)
>   		return IRQ_NONE;
>   
>   	evt->count = count;


I did see this issue previously ([1] on 5.10) on SAR2130 (upstreamed 
recently). Can you help check if the issue is same on your end if you 
can reproduce it easily. Thinh also provided some debug pointers to 
check suspecting it to be a HW issue.

As per the comments from Thinh, he suggested to add a error log as well 
when this happens [2].

[1]: 
https://lore.kernel.org/all/20230521100330.22478-1-quic_kriskura@quicinc.com/

[2]: 
https://lore.kernel.org/all/20230525001822.ane3zcyyifj2kuwx@synopsys.com/

Regards,
Krishna,