Re: [PATCH] usb: gadget: pch_udc: fix use after free

[Andy Shevchenko]

On Wed, Nov 6, 2019 at 10:41 AM Pan Bian <bianpan2016@xxxxxxx> wrote:
>
> The next field of the DMA descriptor is written after releasing the
> descriptor, which may result in a use-after-free issue. Set the value of
> the field before it is released to fix the bug.
>

Had you chance to read the discussion [1]?
I Cc to Gustavo to hear from him about destiny of the change.

[1]: http://lkml.iu.edu/hypermail/linux/kernel/1702.1/00843.html

> Signed-off-by: Pan Bian <bianpan2016@xxxxxxx>
> ---
>  drivers/usb/gadget/udc/pch_udc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/udc/pch_udc.c b/drivers/usb/gadget/udc/pch_udc.c
> index 265dab2bbfac..c5b8ec908aab 100644
> --- a/drivers/usb/gadget/udc/pch_udc.c
> +++ b/drivers/usb/gadget/udc/pch_udc.c
> @@ -1518,8 +1518,8 @@ static void pch_udc_free_dma_chain(struct pch_udc_dev *dev,
>                 /* do not free first desc., will be done by free for request */
>                 td = phys_to_virt(addr);
>                 addr2 = (dma_addr_t)td->next;
> -               dma_pool_free(dev->data_requests, td, addr);
>                 td->next = 0x00;
> +               dma_pool_free(dev->data_requests, td, addr);
>                 addr = addr2;
>         }
>         req->chain_len = 1;
> --
> 2.7.4
>


-- 
With Best Regards,
Andy Shevchenko