From: Peter Chen <peter.chen@kernel.org>
To: Jack Pham <jackp@codeaurora.org>
Cc: Felipe Balbi <balbi@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-usb@vger.kernel.org, linux-arm-msm@vger.kernel.org,
Peter Chen <peter.chen@nxp.com>,
Sandeep Maheswaram <sanm@codeaurora.org>,
Wesley Cheng <wcheng@codeaurora.org>,
Elliot Berman <eberman@codeaurora.org>,
Prasad Sodagudi <psodagud@codeaurora.org>
Subject: Re: [PATCH v2] usb: dwc3: gadget: Free gadget structure only after freeing endpoints
Date: Sat, 8 May 2021 14:21:40 +0800 [thread overview]
Message-ID: <20210508062140.GA3159@nchen> (raw)
In-Reply-To: <20210501093558.7375-1-jackp@codeaurora.org>
On 21-05-01 02:35:58, Jack Pham wrote:
> As part of commit e81a7018d93a ("usb: dwc3: allocate gadget structure
> dynamically") the dwc3_gadget_release() was added which will free
> the dwc->gadget structure upon the device's removal when
> usb_del_gadget_udc() is called in dwc3_gadget_exit().
>
> However, simply freeing the gadget results a dangling pointer
> situation: the endpoints created in dwc3_gadget_init_endpoints()
> have their dep->endpoint.ep_list members chained off the list_head
> anchored at dwc->gadget->ep_list. Thus when dwc->gadget is freed,
> the first dwc3_ep in the list now has a dangling prev pointer and
> likewise for the next pointer of the dwc3_ep at the tail of the list.
> The dwc3_gadget_free_endpoints() that follows will result in a
> use-after-free when it calls list_del().
>
> This was caught by enabling KASAN and performing a driver unbind.
> The recent commit 568262bf5492 ("usb: dwc3: core: Add shutdown
> callback for dwc3") also exposes this as a panic during shutdown.
>
> There are a few possibilities to fix this. One could be to perform
> a list_del() of the gadget->ep_list itself which removes it from
> the rest of the dwc3_ep chain.
>
> Another approach is what this patch does, by splitting up the
> usb_del_gadget_udc() call into its separate "del" and "put"
> components. This allows dwc3_gadget_free_endpoints() to be
> called before the gadget is finally freed with usb_put_gadget().
>
> Fixes: e81a7018d93a ("usb: dwc3: allocate gadget structure dynamically")
> Signed-off-by: Jack Pham <jackp@codeaurora.org>
> ---
> v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart
> when manually recomposing the patch)
>
> drivers/usb/dwc3/gadget.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index 6eab78f8a1a7..c7e5f5a07f3b 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -4062,8 +4062,9 @@ int dwc3_gadget_init(struct dwc3 *dwc)
>
> void dwc3_gadget_exit(struct dwc3 *dwc)
> {
> - usb_del_gadget_udc(dwc->gadget);
> + usb_del_gadget(dwc->gadget);
> dwc3_gadget_free_endpoints(dwc);
> + usb_put_gadget(dwc->gadget);
> dma_free_coherent(dwc->sysdev, DWC3_BOUNCE_SIZE, dwc->bounce,
> dwc->bounce_addr);
> kfree(dwc->setup_buf);
> --
Reviewed-by: Peter Chen <peter.chen@kernel.org>
--
Thanks,
Peter Chen
next prev parent reply other threads:[~2021-05-08 6:21 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-01 9:30 [PATCH] usb: dwc3: gadget: Free gadget structure only after freeing endpoints Jack Pham
2021-05-01 9:35 ` [PATCH v2] " Jack Pham
2021-05-06 16:02 ` Jack Pham
2021-05-08 6:21 ` Peter Chen [this message]
2021-05-10 12:12 ` Felipe Balbi
2021-05-01 11:48 ` [PATCH] " kernel test robot
2021-05-01 13:11 ` kernel test robot
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