On 4.3.2020 5.16, Macpaul Lin wrote: > On Tue, 2020-02-04 at 17:44 +0800, Mathias Nyman wrote: >> On 1.2.2020 13.20, Macpaul Lin wrote: >>> 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 >>> >> >> Thanks, >> Could you help me find out which line of code xhci_irq+0x728 is in your case. >> >> As Guenter pointed out there is a risk of turning the NULL pointer dereference >> into a use after free if we just solve this by setting xhci->shared_hcd = NULL >> later. >> >> If you still have that kernel around, and xhci is compiled in: >> gdb vmlinux >> gdb li *(xhci_irq+0x728) >> > > Sorry that I couldn't get back to you soon. The internal code version > for this issue was really old and a little bit difficult to rewind to > that version. > However, I think the following dump might be correct for the code base. > > (gdb) li *(xhci_irq+0x728) > 0xffffff8008cc8634 is in xhci_irq (*stripped* > kernel-4.14/drivers/usb/host/xhci.h:1694). > 1689 */ > 1690 #define XHCI_MAX_REXIT_TIMEOUT_MS 20 > 1691 > 1692 static inline unsigned int hcd_index(struct usb_hcd *hcd) > 1693 { > 1694 if (hcd->speed >= HCD_USB3) > 1695 return 0; > 1696 else > 1697 return 1; > 1698 } > (gdb) > > Thanks > Macpaul Lin > Ah, it was a 4.14 kernel. This should be fixed in 4.20 with patch: 1245374e9b83 xhci: handle port status events for removed USB3 hcd Port arrays/structures were changed completely in 4.18 Something like the below should work for 4.14: diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 61fa3007a74a..e7367b9f19c5 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -1640,6 +1640,12 @@ static void handle_port_status(struct xhci_hcd *xhci, if ((major_revision == 0x03) != (hcd->speed >= HCD_USB3)) hcd = xhci->shared_hcd; + if (!hcd) { + xhci_dbg(xhci, "No hcd found for port %u event\n", port_id); + bogus_port_status = true; + goto cleanup; + } + if (major_revision == 0) { xhci_warn(xhci, "Event for port %u not in " "Extended Capabilities, ignoring.\n", -Mathias
