xhci: Fix null pointer dereference in remove if xHC has only one roothub

jira VULN-69751
cve CVE-2022-49962
commit-author Mathias Nyman <mathias.nyman@linux.intel.com>
commit 4a593a6

The remove path in xhci platform driver tries to remove and put both main
and shared hcds even if only a main hcd exists (one roothub)

This causes a null pointer dereference in reboot for those controllers.

Check that the shared_hcd exists before trying to remove it.

Fixes: e0fe986 ("usb: host: xhci-plat: prepare operation w/o shared hcd")
	Reported-by: Alexey Sheplyakov <asheplyakov@basealt.ru>
	Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20220825150840.132216-2-mathias.nyman@linux.intel.com
	Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 4a593a6)
	Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

drivers/usb/host/xhci-plat.c

@@ -405,12 +405,17 @@ static int xhci_plat_remove(struct platform_device *dev)
 	pm_runtime_get_sync(&dev->dev);
 	xhci->xhc_state |= XHCI_STATE_REMOVING;
 
-	usb_remove_hcd(shared_hcd);
-	xhci->shared_hcd = NULL;
+	if (shared_hcd) {
+		usb_remove_hcd(shared_hcd);
+		xhci->shared_hcd = NULL;
+	}
+
 	usb_phy_shutdown(hcd->usb_phy);
 
 	usb_remove_hcd(hcd);
-	usb_put_hcd(shared_hcd);
+
+	if (shared_hcd)
+		usb_put_hcd(shared_hcd);
 
 	clk_disable_unprepare(clk);
 	clk_disable_unprepare(reg_clk);