[PATCH v2] usb: xhci: Check endpoint is valid before dereferencing it

[Jimmy Hu]

When the host controller is not responding, all URBs queued to all
endpoints need to be killed. This can cause a kernel panic if we
dereference an invalid endpoint.

Fix this by using xhci_get_virt_ep() helper to find the endpoint and
checking if the endpoint is valid before dereferencing it.

[233311.853271] xhci-hcd xhci-hcd.1.auto: xHCI host controller not responding, assume dead
[233311.853393] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000e8

[233311.853964] pc : xhci_hc_died+0x10c/0x270
[233311.853971] lr : xhci_hc_died+0x1ac/0x270

[233311.854077] Call trace:
[233311.854085]  xhci_hc_died+0x10c/0x270
[233311.854093]  xhci_stop_endpoint_command_watchdog+0x100/0x1a4
[233311.854105]  call_timer_fn+0x50/0x2d4
[233311.854112]  expire_timers+0xac/0x2e4
[233311.854118]  run_timer_softirq+0x300/0xabc
[233311.854127]  __do_softirq+0x148/0x528
[233311.854135]  irq_exit+0x194/0x1a8
[233311.854143]  __handle_domain_irq+0x164/0x1d0
[233311.854149]  gic_handle_irq.22273+0x10c/0x188
[233311.854156]  el1_irq+0xfc/0x1a8
[233311.854175]  lpm_cpuidle_enter+0x25c/0x418 [msm_pm]
[233311.854185]  cpuidle_enter_state+0x1f0/0x764
[233311.854194]  do_idle+0x594/0x6ac
[233311.854201]  cpu_startup_entry+0x7c/0x80
[233311.854209]  secondary_start_kernel+0x170/0x198

Fixes: 50e8725e7c42 ("xhci: Refactor command watchdog and fix split string.")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jimmy Hu <hhhuuu@xxxxxxxxxx>
---
 drivers/usb/host/xhci-ring.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index ddc30037f9ce..f5b0e1ce22af 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1169,7 +1169,10 @@ static void xhci_kill_endpoint_urbs(struct xhci_hcd *xhci,
 	struct xhci_virt_ep *ep;
 	struct xhci_ring *ring;
 
-	ep = &xhci->devs[slot_id]->eps[ep_index];
+	ep = xhci_get_virt_ep(xhci, slot_id, ep_index);
+	if (!ep)
+		return;
+
 	if ((ep->ep_state & EP_HAS_STREAMS) ||
 			(ep->ep_state & EP_GETTING_NO_STREAMS)) {
 		int stream_id;
-- 
2.39.0.314.g84b9a713c41-goog