linux-kernel - Re: [PATCH] usb: gadget: pch

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Message-ID: <CAHp75VeQ_3mConCN=u9O_Ckz9O+awHU=s+d3Kn6R35ZfzzAJKg@mail.gmail.com>
Date:   Wed, 6 Nov 2019 10:54:32 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Pan Bian <bianpan2016@....com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Colin Ian King <colin.king@...onical.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Chuhong Yuan <hslester96@...il.com>,
        USB <linux-usb@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: gadget: pch_udc: fix use after free

On Wed, Nov 6, 2019 at 10:41 AM Pan Bian <bianpan2016@....com> 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@....com>
> ---
>  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