On Fri, 2020-01-31 at 16:50 +0200, Mathias Nyman wrote: > On 17.1.2020 9.41, Macpaul Lin wrote: > > According to NULL pointer fix: https://tinyurl.com/uqft5ra > > xhci: Fix NULL pointer dereference with xhci_irq() for shared_hcd > > The similar issue has also been found in QC activities in Mediatek. > > > > Here quote the description from the referenced patch as follows. > > "Commit ("f068090426ea xhci: Fix leaking USB3 shared_hcd > > at xhci removal") sets xhci_shared_hcd to NULL without > > stopping xhci host. This results into a race condition > > where shared_hcd (super speed roothub) related interrupts > > are being handled with xhci_irq happens when the > > xhci_plat_remove is called and shared_hcd is set to NULL. > > Fix this by setting the shared_hcd to NULL only after the > > controller is halted and no interrupts are generated." > > > > Signed-off-by: Sriharsha Allenki <sallenki@xxxxxxxxxxxxxx> > > Signed-off-by: Macpaul Lin <macpaul.lin@xxxxxxxxxxxx> > > --- > > drivers/usb/host/xhci-mtk.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c > > index b18a6baef204..c227c67f5dc5 100644 > > --- a/drivers/usb/host/xhci-mtk.c > > +++ b/drivers/usb/host/xhci-mtk.c > > @@ -593,11 +593,11 @@ static int xhci_mtk_remove(struct platform_device *dev) > > struct usb_hcd *shared_hcd = xhci->shared_hcd; > > > > usb_remove_hcd(shared_hcd); > > - xhci->shared_hcd = NULL; > > device_init_wakeup(&dev->dev, false); > > > > usb_remove_hcd(hcd); > > usb_put_hcd(shared_hcd); > > + xhci->shared_hcd = NULL; > > usb_put_hcd(hcd); > > xhci_mtk_sch_exit(mtk); > > xhci_mtk_clks_disable(mtk); > > > > Could you share details of the NULL pointer dereference, (backtrace). This bug was found by our QA staff while doing 500 times plug-in and plug-out devices. The backtrace I have was recorded by QA and I didn't reproduce this issue on my own environment. However, after applied this patch the issue seems resolve. Here is the backtrace: Exception Class: Kernel (KE) PC is at [<ffffff8008cccbc0>] xhci_irq+0x728/0x2364 LR is at [<ffffff8008ccc788>] xhci_irq+0x2f0/0x2364 Current Executing Process: [iptables, 859][netdagent, 770] Backtrace: [<ffffff80080ead58>] __atomic_notifier_call_chain+0xa8/0x130 [<ffffff80080eb6d4>] notify_die+0x84/0xac [<ffffff800808e874>] die+0x1d8/0x3b8 [<ffffff80080a89b0>] __do_kernel_fault+0x178/0x188 [<ffffff80080a81b4>] do_page_fault+0x44/0x3b0 [<ffffff80080a811c>] do_translation_fault+0x44/0x98 [<ffffff8008080e08>] do_mem_abort+0x4c/0x128 [<ffffff80080832d0>] el1_da+0x24/0x3c [<ffffff8008cccbc0>] xhci_irq+0x728/0x2364 [<ffffff8008c98804>] usb_hcd_irq+0x2c/0x44 [<ffffff8008179bb0>] __handle_irq_event_percpu+0x26c/0x4a4 [<ffffff8008179ec8>] handle_irq_event+0x5c/0xd0 [<ffffff800817e3c0>] handle_fasteoi_irq+0x10c/0x1e0 [<ffffff80081787b0>] __handle_domain_irq+0x32c/0x738 [<ffffff800808159c>] gic_handle_irq+0x174/0x1c4 [<ffffff8008083cf8>] el0_irq_naked+0x50/0x5c [<ffffffffffffffff>] 0xffffffffffffffff > The USB3 hcd is already removed when xhci->shared_hcd is set to NULL. > We might want to add some checks to make sure we are not using the removed > hcd anymore in that codepath anymore. > > -Mathias Thanks, Macpaul Lin
