Messages in this thread |  | | From | Jia-Ju Bai <> | Subject | [BUG] usb: xhci: Possible resource leaks when xhci_run() fails | Date | Tue, 14 May 2019 22:58:05 +0800 |
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xhci_pci_setup() is assigned to hc_driver.reset; xhci_run() is assigned to hc_driver.start(); xhci_stop() is assigned to hc_driver.stop().
xhci_pci_setup() calls xhci_gen_setup, which calls xhci_init(). And xhci_init() calls xhci_mem_init() to allocate resources.
xhci_stop() calls xhci_mem_cleanup(), to release the resources allocated in xhci_mem_init() (also namely xhci_pci_setup()).
xhci_run() can fail, because xhci_try_enable_msi() or xhci_alloc_command() in this function can fail.
In drivers/usb/core/hcd.c: retval = hcd->driver->reset(hcd); if (retval < 0) { ...... goto err_hcd_driver_setup; } ...... retval = hcd->driver->start(hcd); if (retval < 0) { ...... goto err_hcd_driver_start; } ....... hcd->driver->stop(hcd); hcd->state = HC_STATE_HALT; clear_bit(HCD_FLAG_POLL_RH, &hcd->flags); del_timer_sync(&hcd->rh_timer); err_hcd_driver_start: if (usb_hcd_is_primary_hcd(hcd) && hcd->irq > 0) free_irq(irqnum, hcd); err_request_irq: err_hcd_driver_setup: err_set_rh_speed: usb_put_invalidate_rhdev(hcd); err_allocate_root_hub: usb_deregister_bus(&hcd->self); err_register_bus: hcd_buffer_destroy(hcd); err_create_buf: usb_phy_roothub_power_off(hcd->phy_roothub); err_usb_phy_roothub_power_on: usb_phy_roothub_exit(hcd->phy_roothub);
Thus, when hcd->driver->reset() succeeds and hcd->driver->start() fails, hcd->driver->stop() is not called.
Namely, when xhci_pci_setup() successfully allocates resources, and xhci_run() fails, xhci_stop() is not called to release the resources. For this reason, resource leaks occur in this case.
I check the code of the ehci driver, uhci driver and ohci driver, and find that they do not have such problem, because: In the ehci driver, ehci_run() (namely hcd->driver->start()) never fails. In the uhci driver, all the resources are allocated in uhci_start (namely hcd->driver->start()), and no resources are allocated in uhci_pci_init() (namely hcd->driver->reset()). In the ohci driver, ohci_setup() (namely hcd->driver->reset()) also allocates resources. But when ohci_start() (namely hcd->driver->start()) is going to fail, ohci_stop() is directly called to release the resources allocated by ohci_setup().
Thus, there are two possible ways of fixing bugs: 1) Call xhci_stop() when xhci_run() is going to fail (like the ohci driver) 2) Move all resource-allocation operations into xhci_run() (like the uhci driver).
I am not sure whether these ways are correct, so I only report bugs.
These bugs are found by a runtime fuzzing tool named FIZZER written by us.
Best wishes, Jia-Ju Bai
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