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From: Felipe Balbi <>
To: Jack Pham <>,
	Greg Kroah-Hartman <>
	Peter Chen <>,
	Sandeep Maheswaram <>,
	Wesley Cheng <>,
	Elliot Berman <>,
	Prasad Sodagudi <>,
	Jack Pham <>
Subject: Re: [PATCH v2] usb: dwc3: gadget: Free gadget structure only after freeing endpoints
Date: Mon, 10 May 2021 15:12:12 +0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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Jack Pham <> writes:

> 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 <>
> ---
> v2: Fix silly typo: usb_del_gadget_put -> usb_put_gadget (brain fart
> when manually recomposing the patch)

I thought I had acked this one already, looks like I missed it:

Acked-by: Felipe Balbi <>


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  parent reply	other threads:[~2021-05-10 13:29 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-01  9:30 [PATCH] " 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
2021-05-10 12:12   ` Felipe Balbi [this message]
2021-05-01 11:48 ` [PATCH] " kernel test robot
2021-05-01 13:11 ` kernel test robot

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