Re: [PATCH] USB: mtu3: tracing: fix pointers dereferencing

[Steven Rostedt <rostedt@goodmis.org>]

On Tue,  4 Aug 2026 12:05:30 +0200
Marek Szyprowski <m.szyprowski@samsung.com> wrote:

> Commit b5cc230af5e5 ("tracing: Warn when an event dereferences a pointer
> in TP_printk()") added a warning then printing an event dereferences

            s/then/when/

> a pointer, because it might be already freed that time.

                                        freed at that time

> 
> MTU3 driver is one of the drivers triggering this warning. Fix it by
> storing also the DMA address in the event structure to avoid

        s/also//

> dereferencing gpd_ring pointer during event printing.
> 
> Fixes: 83374e035b62 ("usb: mtu3: add tracepoints to help debug")
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>  drivers/usb/mtu3/mtu3_trace.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/mtu3/mtu3_trace.h b/drivers/usb/mtu3/mtu3_trace.h
> index 89870175d635..b24c6411a8cf 100644
> --- a/drivers/usb/mtu3/mtu3_trace.h
> +++ b/drivers/usb/mtu3/mtu3_trace.h
> @@ -224,6 +224,7 @@ DECLARE_EVENT_CLASS(mtu3_log_ep,
>  		__field(unsigned int, flags)
>  		__field(unsigned int, direction)
>  		__field(struct mtu3_gpd_ring *, gpd_ring)
> +		__field(dma_addr_t, gpd_ring_dma)
>  	),
>  	TP_fast_assign(
>  		__assign_str(name);
> @@ -235,12 +236,13 @@ DECLARE_EVENT_CLASS(mtu3_log_ep,
>  		__entry->flags = mep->flags;
>  		__entry->direction = mep->is_in;
>  		__entry->gpd_ring = &mep->gpd_ring;
> +		__entry->gpd_ring_dma = __entry->gpd_ring->dma;
>  	),
>  	TP_printk("%s: type %s maxp %d slot %d mult %d burst %d ring %p/%pad flags %c:%c%c%c:%c",
>  		__get_str(name), usb_ep_type_string(__entry->type),
>  		__entry->maxp, __entry->slot,
>  		__entry->mult, __entry->maxburst,
> -		__entry->gpd_ring, &__entry->gpd_ring->dma,
> +		__entry->gpd_ring, &__entry->gpd_ring_dma,
>  		__entry->flags & MTU3_EP_ENABLED ? 'E' : 'e',
>  		__entry->flags & MTU3_EP_STALL ? 'S' : 's',
>  		__entry->flags & MTU3_EP_WEDGE ? 'W' : 'w',

Reviewed-by: Steven Rostedt <rostedt@goodmis.org>

Thanks for fixing this!

-- Steve