Re: [BUG] usb: xhci: Possible resource leaks when xhci_run() fails

[Jia-Ju Bai]

On 2019/5/15 0:55, Greg KH wrote:
> On Tue, May 14, 2019 at 10:58:05PM +0800, Jia-Ju Bai wrote:
> > 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.
> Can you create a patch to show how you would fix this potential issue?
> Given that making this type of thing fail is pretty rare, it's not a
> real high priority to get to, so it might be a while for anyone here to
> look at it.

Okay, I will send a patch soon.


Best wishes,
Jia-Ju Bai