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)
-Mathias
