[PATCH] usb: gadget: lpc32xx_udc: drain the pullup work on removal

[Hyunjung Ko <hj351016@gmail.com>]

isp1301_pullup_enable() schedules udc->pullup_job to perform the slow
isp1301 i2c pull-up access from process context. The work handler
(pullup_work) dereferences udc and touches the isp1301 i2c client.

udc is allocated with devm_kmemdup(), so devres frees it after
lpc32xx_udc_remove() returns. remove() calls pullup(udc, 0) -- which can
schedule pullup_job -- and also puts the isp1301 i2c client, but it never
drains the work. A pullup_job still pending can then run after udc has
been freed (and the isp1301 client put), dereferencing freed memory -- a
use-after-free.

Cancel pullup_job in lpc32xx_udc_remove(), after the final pullup(udc, 0)
and before the udc and its isp1301 client are released.

Found by static analysis; not runtime-reproduced (needs LPC32xx USB
gadget hardware with the isp1301 transceiver).

Fixes: 24a28e428351 ("USB: gadget driver for LPC32xx")
Cc: stable@vger.kernel.org
Signed-off-by: Hyunjung Ko <hj351016@gmail.com>
---
 drivers/usb/gadget/udc/lpc32xx_udc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/usb/gadget/udc/lpc32xx_udc.c b/drivers/usb/gadget/udc/lpc32xx_udc.c
index 94355d3..210fa1f 100644
--- a/drivers/usb/gadget/udc/lpc32xx_udc.c
+++ b/drivers/usb/gadget/udc/lpc32xx_udc.c
@@ -3186,6 +3186,13 @@ static void lpc32xx_udc_remove(struct platform_device *pdev)
 	udc_clk_set(udc, 1);
 	udc_disable(udc);
 	pullup(udc, 0);

+	/*
+	 * pullup() schedules pullup_job to do the slow isp1301 i2c access; the
+	 * work dereferences udc, so drain it before the devm-allocated udc (and
+	 * the isp1301 i2c client it uses) are released.
+	 */
+	cancel_work_sync(&udc->pullup_job);
+
 	device_init_wakeup(&pdev->dev, 0);
 	remove_debug_file(udc);

--
2.43.0