linux-kernel - [PATCH] usb: phy: fsl-usb: Fix use-after-free in delayed work during device removal

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Message-Id: <20251205034831.12846-1-duoming@zju.edu.cn>
Date: Fri,  5 Dec 2025 11:48:31 +0800
From: Duoming Zhou <duoming@....edu.cn>
To: linux-usb@...r.kernel.org
Cc: linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org,
	kuba@...nel.org,
	alexander.deucher@....com,
	Jonathan.Cameron@...wei.com,
	akpm@...ux-foundation.org,
	johannes.berg@...el.com,
	krzk@...nel.org,
	Duoming Zhou <duoming@....edu.cn>,
	stable@...nel.org
Subject: [PATCH] usb: phy: fsl-usb: Fix use-after-free in delayed work during device removal

The delayed work item otg_event is initialized in fsl_otg_conf() and
scheduled under two conditions:
1. When a host controller binds to the OTG controller.
2. When the USB ID pin state changes (cable insertion/removal).

A race condition occurs when the device is removed via fsl_otg_remove():
the fsl_otg instance may be freed while the delayed work is still pending
or executing. This leads to use-after-free when the work function
fsl_otg_event() accesses the already freed memory.

The problematic scenario:

(detach thread)            | (delayed work)
fsl_otg_remove()           |
  kfree(fsl_otg_dev) //FREE| fsl_otg_event()
                           |   og = container_of(...) //USE
                           |   og-> //USE

Fix this by calling disable_delayed_work_sync() in fsl_otg_remove()
before deallocating the fsl_otg structure. This ensures the delayed work
is properly canceled and completes execution prior to memory deallocation.

This bug was identified through static analysis.

Fixes: 0807c500a1a6 ("USB: add Freescale USB OTG Transceiver driver")
Cc: stable@...nel.org
Signed-off-by: Duoming Zhou <duoming@....edu.cn>
---
 drivers/usb/phy/phy-fsl-usb.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/phy/phy-fsl-usb.c b/drivers/usb/phy/phy-fsl-usb.c
index 40ac68e52ce..e266a47c4d4 100644
--- a/drivers/usb/phy/phy-fsl-usb.c
+++ b/drivers/usb/phy/phy-fsl-usb.c
@@ -988,6 +988,7 @@ static void fsl_otg_remove(struct platform_device *pdev)
 {
 	struct fsl_usb2_platform_data *pdata = dev_get_platdata(&pdev->dev);

+	disable_delayed_work_sync(&fsl_otg_dev->otg_event);
 	usb_remove_phy(&fsl_otg_dev->phy);
 	free_irq(fsl_otg_dev->irq, fsl_otg_dev);

-- 
2.34.1