On 17.11.2023 9.21, Kuen-Han Tsai wrote:
The null pointer dereference happens when xhci_free_dev() frees the
xhci->devs[slot_id] virtual device while xhci_urb_enqueue() is
processing a urb and checking the max packet size.
[106913.850735][ T2068] usb 2-1: USB disconnect, device number 2
[106913.856999][ T4618] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
[106913.857488][ T4618] Call trace:
[106913.857491][ T4618] xhci_check_maxpacket+0x30/0x2dc
[106913.857494][ T4618] xhci_urb_enqueue+0x24c/0x47c
[106913.857498][ T4618] usb_hcd_submit_urb+0x1f4/0xf34
[106913.857501][ T4618] usb_submit_urb+0x4b8/0x4fc
[106913.857503][ T4618] usb_control_msg+0x144/0x238
[106913.857507][ T4618] do_proc_control+0x1f0/0x5bc
[106913.857509][ T4618] usbdev_ioctl+0xdd8/0x15a8
This patch adds a spinlock to the xhci_urb_enqueue function to make sure
xhci_free_dev() and xhci_urb_enqueue() do not race and cause null
pointer dereference.
Thanks, nice catch
This patch does however need some additional tuning
Signed-off-by: Kuen-Han Tsai <khtsai@xxxxxxxxxx>
---
drivers/usb/host/xhci.c | 38 ++++++++++++++++++++++++--------------
1 file changed, 24 insertions(+), 14 deletions(-)
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 884b0898d9c9..e0766ebeff0e 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -1522,23 +1522,32 @@ static int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
struct urb_priv *urb_priv;
int num_tds;
- if (!urb)
- return -EINVAL;
- ret = xhci_check_args(hcd, urb->dev, urb->ep,
- true, true, __func__);
- if (ret <= 0)
- return ret ? ret : -EINVAL;
+ spin_lock_irqsave(&xhci->lock, flags);
+
+ if (!urb) {
+ ret = -EINVAL;
+ goto done;
+ }
+
+ ret = xhci_check_args(hcd, urb->dev, urb->ep, true, true, __func__);
+ if (ret <= 0) {
+ ret = ret ? ret : -EINVAL;
+ goto done;
+ }
slot_id = urb->dev->slot_id;
ep_index = xhci_get_endpoint_index(&urb->ep->desc);
ep_state = &xhci->devs[slot_id]->eps[ep_index].ep_state;
- if (!HCD_HW_ACCESSIBLE(hcd))
- return -ESHUTDOWN;
+ if (!HCD_HW_ACCESSIBLE(hcd)) {
+ ret = -ESHUTDOWN;
+ goto done;
+ }
if (xhci->devs[slot_id]->flags & VDEV_PORT_ERROR) {
xhci_dbg(xhci, "Can't queue urb, port error, link inactive\n");
- return -ENODEV;
+ ret = -ENODEV;
+ goto done;
}
if (usb_endpoint_xfer_isoc(&urb->ep->desc))
@@ -1552,8 +1561,10 @@ static int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
num_tds = 1;
urb_priv = kzalloc(struct_size(urb_priv, td, num_tds), mem_flags);
kzalloc with spinlock held, should preferably be moved outside lock, otherwise should use GFP_ATOMIC
- if (!urb_priv)
- return -ENOMEM;
+ if (!urb_priv) {
+ ret = -ENOMEM;
+ goto done;
+ }
urb_priv->num_tds = num_tds;
urb_priv->num_tds_done = 0;
@@ -1571,13 +1582,11 @@ static int xhci_urb_enqueue(struct usb_hcd *hcd, struct urb *urb, gfp_t mem_flag
xhci_check_maxpacket() called here can't be called with spinlock held
if (ret < 0) {
xhci_urb_free_priv(urb_priv);
urb->hcpriv = NULL;
- return ret;
+ goto done;
Thanks
Mathias
