usb: otg-fsm: Fix hrtimer list corruption

The HNP work can be re-scheduled while it's still in-fly. This results in
re-initialization of the busy work, resetting the hrtimer's list node of
the work and crashing kernel with null dereference within kernel/timer
once work's timer is expired. It's very easy to trigger this problem by
re-plugging USB cable quickly. Initialize HNP work only once to fix this
trouble.

 Unable to handle kernel NULL pointer dereference at virtual address 00000126)
 ...
 PC is at __run_timers.part.0+0x150/0x228
 LR is at __next_timer_interrupt+0x51/0x9c
 ...
 (__run_timers.part.0) from [<c0187a2b>] (run_timer_softirq+0x2f/0x50)
 (run_timer_softirq) from [<c01013ad>] (__do_softirq+0xd5/0x2f0)
 (__do_softirq) from [<c012589b>] (irq_exit+0xab/0xb8)
 (irq_exit) from [<c0170341>] (handle_domain_irq+0x45/0x60)
 (handle_domain_irq) from [<c04c4a43>] (gic_handle_irq+0x6b/0x7c)
 (gic_handle_irq) from [<c0100b65>] (__irq_svc+0x65/0xac)

Cc: stable@vger.kernel.org
Acked-by: Peter Chen <peter.chen@kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20210717182134.30262-6-digetx@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/common/usb-otg-fsm.c

@@ -193,7 +193,11 @@ static void otg_start_hnp_polling(struct otg_fsm *fsm)
 	if (!fsm->host_req_flag)
 		return;
 
+	if (!fsm->hnp_work_inited) {
 		INIT_DELAYED_WORK(&fsm->hnp_polling_work, otg_hnp_polling_work);
+		fsm->hnp_work_inited = true;
+	}
+
 	schedule_delayed_work(&fsm->hnp_polling_work,
 					msecs_to_jiffies(T_HOST_REQ_POLL));
 }

include/linux/usb/otg-fsm.h

@@ -196,6 +196,7 @@ struct otg_fsm {
 	struct mutex lock;
 	u8 *host_req_flag;
 	struct delayed_work hnp_polling_work;
+	bool hnp_work_inited;
 	bool state_changed;
 };