On 22.12.2022 13.52, Ladislav Michl wrote:
On Thu, Dec 22, 2022 at 01:08:47PM +0200, Mathias Nyman wrote:
On 22.12.2022 11.01, Ladislav Michl wrote:
On Thu, Dec 22, 2022 at 07:29:12AM +0000, Jimmy Hu wrote:
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@vger.kernel.org Signed-off-by: Jimmy Hu hhhuuu@google.com
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;xhci_get_virt_ep also adds check for slot_id == 0. It changes behaviour, do we really want to skip that slot? Original code went from 0 to MAX_HC_SLOTS-1.
It seems to be off by one to me. Am I missing anything?
slot_id 0 is always invalid, so this is a good change.
I see. Now reading more carefully: #define HCS_MAX_SLOTS(p) (((p) >> 0) & 0xff) #define MAX_HC_SLOTS 256 So the loop should go: for (i = 1; i <= HCS_MAX_SLOTS(xhci->hcs_params1); i++)
yes
Also, what about passing ep directly to xhci_kill_endpoint_urbs and do the check in xhci_hc_died? Not even compile tested:
passing ep to a function named kill_endpoint_urbs() sound like the right thing to do, but as a generic change.
I think its a good idea to first do a targeted fix for this null pointer issue that we can send to stable fist.
Agree. But I still do not understand the root cause. There is a check for NULL xhci->devs[i] already, so patch does not add much more, except for test for slot_id == 0. And the eps array is just array of struct xhci_virt_ep, not a pointers to them, so &xhci->devs[i]->eps[j] should be always valid pointer. However struct xhci_ring in each eps is allocated and not protected by any lock here. Is that correct?
I think root cause is that freeing xhci->devs[i] and including rings isn't protected by the lock, this happens in xhci_free_virt_device() called by xhci_free_dev(), which in turn may be called by usbcore at any time
So xhci->devs[i] might just suddenly disappear
Patch just checks more often if xhci->devs[i] is valid, between every endpoint. So the race between xhci_free_virt_device() and xhci_kill_endpoint_urbs() doesn't trigger null pointer deref as easily.
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index ddc30037f9ce..5dac483c562a 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -1162,14 +1162,12 @@ static void xhci_kill_ring_urbs(struct xhci_hcd *xhci, struct xhci_ring *ring) } static void xhci_kill_endpoint_urbs(struct xhci_hcd *xhci,
int slot_id, int ep_index)
struct xhci_virt_ep *ep)
- struct xhci_virt_ep *ep; struct xhci_ring *ring;
- ep = &xhci->devs[slot_id]->eps[ep_index]; if ((ep->ep_state & EP_HAS_STREAMS) || (ep->ep_state & EP_GETTING_NO_STREAMS)) { int stream_id;
@@ -1180,18 +1178,12 @@ static void xhci_kill_endpoint_urbs(struct xhci_hcd *xhci, if (!ring) continue;
xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,"Killing URBs for slot ID %u, ep index %u, stream %u",slot_id, ep_index, stream_id); xhci_kill_ring_urbs(xhci, ring); }xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,"Killing URBs for slot ID %u, ep index %u",slot_id, ep_index); xhci_kill_ring_urbs(xhci, ring);@@ -1217,6 +1209,7 @@ static void xhci_kill_endpoint_urbs(struct xhci_hcd *xhci, void xhci_hc_died(struct xhci_hcd *xhci) { int i, j;
- struct xhci_virt_ep *ep; if (xhci->xhc_state & XHCI_STATE_DYING) return;
@@ -1227,11 +1220,14 @@ void xhci_hc_died(struct xhci_hcd *xhci) xhci_cleanup_command_queue(xhci); /* return any pending urbs, remove may be waiting for them */
- for (i = 0; i <= HCS_MAX_SLOTS(xhci->hcs_params1); i++) {
- for (i = 0; i < HCS_MAX_SLOTS(xhci->hcs_params1); i++) { if (!xhci->devs[i]) continue;
for (j = 0; j < 31; j++)xhci_kill_endpoint_urbs(xhci, i, j);
for (j = 0; j < EP_CTX_PER_DEV; j++) {ep = &xhci->devs[i]->eps[j];if (ep)xhci_kill_endpoint_urbs(xhci, ep);}This does loop a bit more than the existing code. With this change its always HCS_MAX_SLOTS * EP_CTX_PER_DEV. Previously best case was just HCS_MAX_SLOTS.
No, that's just the same:
you're right, incorrectly read that your patch deleted the "if (!xhci->devs[i]) continue;" lines.
Thanks -Mathias