On 21.4.2022 15.21, Fu Zixuan wrote:
> On Thu, 21 Apr 2022 at 20:06, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>>
>> On Thu, Apr 21, 2022 at 07:55:28PM +0800, Fu Zixuan wrote:
>>> On Thu, 21 Apr 2022 at 18:07, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>>>>
>>>> On Thu, Apr 21, 2022 at 05:42:36PM +0800, Zixuan Fu wrote:
>>>>> In xhci_create_rhub_port_array(), when rhub->num_ports is zero,
>>>>> rhub->ports would not be set; when kcalloc_node() fails, rhub->ports
>>>>> would be set to NULL. In these two cases, xhci_create_rhub_port_array()
>>>>> just returns void, and thus its callers are unaware of the error.
>>>>>
>>>>> Then rhub->ports is dereferenced in xhci_usb3_hub_descriptor() or
>>>>> xhci_usb2_hub_descriptor().
>>>>>
>>>>> To fix the bug, xhci_setup_port_arrays() should return an integer to
>>>>> indicate a possible error, and its callers should handle the error.
>>>>>
>>>>> Here is the log when this bug occurred in our fault-injection testing:
>>>>>
>>>>> [ 24.001309] BUG: kernel NULL pointer dereference, address: 0000000000000000
>>>>> ...
>>>>> [ 24.003992] RIP: 0010:xhci_hub_control+0x3f5/0x60d0 [xhci_hcd]
>>>>> ...
>>>>> [ 24.009803] Call Trace:
>>>>> [ 24.010014] <TASK>
>>>>> [ 24.011310] usb_hcd_submit_urb+0x1233/0x1fd0
>>>>> [ 24.017071] usb_start_wait_urb+0x115/0x310
>>>>> [ 24.017641] usb_control_msg+0x28a/0x450
>>>>> [ 24.019046] hub_probe+0xb16/0x2320
>>>>> [ 24.019757] usb_probe_interface+0x4f1/0x930
>>>>> [ 24.019765] really_probe+0x33d/0x970
>>>>> [ 24.019768] __driver_probe_device+0x157/0x210
>>>>> [ 24.019772] driver_probe_device+0x4f/0x340
>>>>> [ 24.019775] __device_attach_driver+0x2ee/0x3a0
>>>>> ...
>>>>>
>>>>> Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
>>>>> Signed-off-by: Zixuan Fu <r33s3n6@xxxxxxxxx>
>>>>> ---
>>>>> drivers/usb/host/xhci-mem.c | 17 ++++++++++++-----
>>>>> 1 file changed, 12 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
>>>>> index bbb27ee2c6a3..024515346c39 100644
>>>>> --- a/drivers/usb/host/xhci-mem.c
>>>>> +++ b/drivers/usb/host/xhci-mem.c
>>>>> @@ -2235,7 +2235,7 @@ static void xhci_add_in_port(struct xhci_hcd *xhci, unsigned int num_ports,
>>>>> /* FIXME: Should we disable ports not in the Extended Capabilities? */
>>>>> }
>>>>>
>>>>> -static void xhci_create_rhub_port_array(struct xhci_hcd *xhci,
>>>>> +static int xhci_create_rhub_port_array(struct xhci_hcd *xhci,
>>>>> struct xhci_hub *rhub, gfp_t flags)
>>>>> {
>>>>> int port_index = 0;
>>>>> @@ -2243,11 +2243,11 @@ static void xhci_create_rhub_port_array(struct xhci_hcd *xhci,
>>>>> struct device *dev = xhci_to_hcd(xhci)->self.sysdev;
>>>>>
>>>>> if (!rhub->num_ports)
>>>>> - return;
>>>>> + return -EINVAL;
>>>>> rhub->ports = kcalloc_node(rhub->num_ports, sizeof(*rhub->ports),
>>>>> flags, dev_to_node(dev));
>>>>> if (!rhub->ports)
>>>>> - return;
>>>>> + return -ENOMEM;
>>>>>
>>>>> for (i = 0; i < HCS_MAX_PORTS(xhci->hcs_params1); i++) {
>>>>> if (xhci->hw_ports[i].rhub != rhub ||
>>>>> @@ -2259,6 +2259,7 @@ static void xhci_create_rhub_port_array(struct xhci_hcd *xhci,
>>>>> if (port_index == rhub->num_ports)
>>>>> break;
>>>>> }
>>>>> + return 0;
>>>>> }
>>>>>
>>>>> /*
>>>>> @@ -2277,6 +2278,7 @@ static int xhci_setup_port_arrays(struct xhci_hcd *xhci, gfp_t flags)
>>>>> int cap_count = 0;
>>>>> u32 cap_start;
>>>>> struct device *dev = xhci_to_hcd(xhci)->self.sysdev;
>>>>> + int ret;
>>>>>
>>>>> num_ports = HCS_MAX_PORTS(xhci->hcs_params1);
>>>>> xhci->hw_ports = kcalloc_node(num_ports, sizeof(*xhci->hw_ports),
>>>>> @@ -2367,8 +2369,13 @@ static int xhci_setup_port_arrays(struct xhci_hcd *xhci, gfp_t flags)
>>>>> * Not sure how the USB core will handle a hub with no ports...
>>>>> */
>>>>>
>>>>> - xhci_create_rhub_port_array(xhci, &xhci->usb2_rhub, flags);
>>>>> - xhci_create_rhub_port_array(xhci, &xhci->usb3_rhub, flags);
>>>>> + ret = xhci_create_rhub_port_array(xhci, &xhci->usb2_rhub, flags);
>>>>> + if (ret)
>>>>> + return ret;
>>>>> +
>>>>> + ret = xhci_create_rhub_port_array(xhci, &xhci->usb3_rhub, flags);
>>>>> + if (ret)
>>>>> + return ret;
>>>>
>>>> What about the memory allocated by the first call to
>>>> xhci_create_rhub_port_array()? Is that now lost? Same for everything
>>>> else allocated before these calls, how is that cleaned up properly?
>>>>
>>>> thanks,
>>>>
>>>> greg k-h
>>>
>>> Thanks for your swift reply. We understand your concern. In fact, we have
>>> checked the related code carefully and found that xhci_create_rhub_port_array()
>>> is only used in xhci_setup_port_arrays(). Moreover, only xhci_mem_init() calls
>>> xhci_setup_port_arrays() and does all cleanup work when it fails. Specifically,
>>> xhci_mem_init() calls xhci_mem_cleanup(), which eventually called
>>> kfree(xhci->usb2_rhub.ports) and kfree(xhci->usb3_rhub.ports).
>>
>> Great, can you mention this in the changelog text to show that you have
>> thought this through and it can be documented as such?
>>
>> thanks,
>>
>> greg k-h
>
> Thanks for your reply! We will do that and submit the patch v2 soon.
>
Good to get this fixed, but there's a series by Heiner Kallweit that adds support
for xHC controllers with just one roothub [1].
It will conflict with this.
We might need to change this a bit so that this can go to stable alone, but still
being being able to somewhat neatly apply that new series on top of this.
1. https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git/log/?h=for-usb-next
Thanks
-Mathias
