Re: [PATCH] usb: dwc3: qcom: fix NULL pointer dereference on dwc3_qcom_read_usb2_speed

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On 14-08-24 05:47 am, Thinh Nguyen wrote:
On Tue, Aug 13, 2024, Faisal Hassan wrote:
Null pointer dereference occurs when accessing 'hcd' to detect speed
from dwc3_qcom_suspend after the xhci-hcd is unbound.
To avoid this issue, ensure to check for NULL in dwc3_qcom_read_usb2_speed.

echo xhci-hcd.0.auto > /sys/bus/platform/drivers/xhci-hcd/unbind
   xhci_plat_remove() -> usb_put_hcd() -> hcd_release() -> kfree(hcd)

   Unable to handle kernel NULL pointer dereference at virtual address
   0000000000000060
   Call trace:
    dwc3_qcom_suspend.part.0+0x17c/0x2d0 [dwc3_qcom]
    dwc3_qcom_runtime_suspend+0x2c/0x40 [dwc3_qcom]
    pm_generic_runtime_suspend+0x30/0x44
    __rpm_callback+0x4c/0x190
    rpm_callback+0x6c/0x80
    rpm_suspend+0x10c/0x620
    pm_runtime_work+0xc8/0xe0
    process_one_work+0x1e4/0x4f4
    worker_thread+0x64/0x43c
    kthread+0xec/0x100
    ret_from_fork+0x10/0x20

Fixes: c5f14abeb52b ("usb: dwc3: qcom: fix peripheral and OTG suspend")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Faisal Hassan <quic_faisalh@xxxxxxxxxxx>
---
  drivers/usb/dwc3/dwc3-qcom.c | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
index 88fb6706a18d..0c7846478655 100644
--- a/drivers/usb/dwc3/dwc3-qcom.c
+++ b/drivers/usb/dwc3/dwc3-qcom.c
@@ -319,13 +319,15 @@ static bool dwc3_qcom_is_host(struct dwc3_qcom *qcom)
  static enum usb_device_speed dwc3_qcom_read_usb2_speed(struct dwc3_qcom *qcom, int port_index)
  {
  	struct dwc3 *dwc = platform_get_drvdata(qcom->dwc3);

What if dwc is not available?

Thats unlikely, dwc3_qcom_suspend() -> dwc3_qcom_is_host() checks for dwc, calls dwc3_qcom_read_usb2_speed() only if dwc is valid. But adding an extra check shouldn't cause harm.

-	struct usb_device *udev;
+	struct usb_device __maybe_unused *udev;

This is odd.... Is there a scenario where you don't want to set
CONFIG_USB if dwc3_qcom is in use?

AFAIK this function is used to get the speeds of each ports, so that wakeup interrupts (dp/dm/ss irqs) can be configured accordingly before going to suspend, which is done during host mode only. So there shouldn't be any scenarios where CONFIG_USB isnt set when this is called.
  	struct usb_hcd __maybe_unused *hcd;
/*
  	 * FIXME: Fix this layering violation.
  	 */
  	hcd = platform_get_drvdata(dwc->xhci);
+	if (!hcd)
+		return USB_SPEED_UNKNOWN;
#ifdef CONFIG_USB

Perhaps this #ifdef shouldn't only be checking this. But that's for
another patch >>   	udev = usb_hub_find_child(hcd->self.root_hub, port_index + 1);
--
2.17.1


BR,
Thinh
Thanks,
Prashanth K




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