linux-kernel - [PATCH 5.10 222/289] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

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Message-Id: <20210517140312.626006320@linuxfoundation.org>
Date:   Mon, 17 May 2021 16:02:27 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Peter Chen <peter.chen@...nel.org>,
        Jack Pham <jackp@...eaurora.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 222/289] usb: dwc3: gadget: Free gadget structure only after freeing endpoints

From: Jack Pham <jackp@...eaurora.org>

[ Upstream commit bb9c74a5bd1462499fe5ccb1e3c5ac40dcfa9139 ]

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")
Reviewed-by: Peter Chen <peter.chen@...nel.org>
Signed-off-by: Jack Pham <jackp@...eaurora.org>
Link: https://lore.kernel.org/r/20210501093558.7375-1-jackp@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 84d1487e9f06..dab9b5fd15a9 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -3948,8 +3948,9 @@ 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);
-- 
2.30.2