From 005c2f4576d9bab5ff97dac4b3d27aafa2f1f153 Mon Sep 17 00:00:00 2001 Message-Id: <005c2f4576d9bab5ff97dac4b3d27aafa2f1f153.1526520264.git.jan.steffens@gmail.com> In-Reply-To: <1d8e17daf031e219d904ef93718081534c9e8cea.1526520263.git.jan.steffens@gmail.com> References: <1d8e17daf031e219d904ef93718081534c9e8cea.1526520263.git.jan.steffens@gmail.com> From: Mathias Nyman Date: Mon, 14 May 2018 11:57:23 +0300 Subject: [PATCH 5/5] xhci: Fix USB3 NULL pointer dereference at logical disconnect. Hub driver will try to disable a USB3 device twice at logical disconnect, racing with xhci_free_dev() callback from the first port disable. This can be triggered with "udisksctl power-off --block-device " or by writing "1" to the "remove" sysfs file for a USB3 device in 4.17-rc4. USB3 devices don't have a similar disabled link state as USB2 devices, and use a U3 suspended link state instead. In this state the port is still enabled and connected. hub_port_connect() first disconnects the device, then later it notices that device is still enabled (due to U3 states) it will try to disable the port again (set to U3). The xhci_free_dev() called during device disable is async, so checking for existing xhci->devs[i] when setting link state to U3 the second time was successful, even if device was being freed. The regression was caused by, and whole thing revealed by, Commit 44a182b9d177 ("xhci: Fix use-after-free in xhci_free_virt_device") which sets xhci->devs[i]->udev to NULL before xhci_virt_dev() returned. and causes a NULL pointer dereference the second time we try to set U3. Fix this by checking xhci->devs[i]->udev exists before setting link state. The original patch went to stable so this fix needs to be applied there as well. Fixes: 44a182b9d177 ("xhci: Fix use-after-free in xhci_free_virt_device") Cc: Reported-by: Jordan Glover Tested-by: Jordan Glover Signed-off-by: Mathias Nyman --- drivers/usb/host/xhci-hub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c index 72ebbc908e19..32cd52ca8318 100644 --- a/drivers/usb/host/xhci-hub.c +++ b/drivers/usb/host/xhci-hub.c @@ -354,7 +354,7 @@ int xhci_find_slot_id_by_port(struct usb_hcd *hcd, struct xhci_hcd *xhci, slot_id = 0; for (i = 0; i < MAX_HC_SLOTS; i++) { - if (!xhci->devs[i]) + if (!xhci->devs[i] || !xhci->devs[i]->udev) continue; speed = xhci->devs[i]->udev->speed; if (((speed >= USB_SPEED_SUPER) == (hcd->speed >= HCD_USB3)) -- 2.17.0