On Sun, 27 Nov 2005, Ville Syrjälä wrote:
> When I tried to reproduce the oops the box would just hang and when I
> eventually got oopses out of it they didn't seem very consistent.
>
> The usbtest module source code is at the end of this message.
>
> So I just compiled 2.6.15-rc2 with some debug options turned on and used
> a serial console to get this trace.
> usb 1-1: new full speed USB device using uhci_hcd and address 2
> input: usbtest as /class/input/input1
> input: usbtest as /class/input/input2
> usb 1-1: USB disconnect, address 2
> slab error in cache_free_debugcheck(): cache `size-2048': double free, or
> memory outside object was overwritten
> [<c01036f7>] dump_stack+0x17/0x20
> [<c013e066>] __slab_error+0x26/0x30
> [<c013fc9a>] cache_free_debugcheck+0x1aa/0x220
> [<c0140771>] kfree+0x51/0x90
> [<d080d034>] usbtest_delete+0x14/0x20 [usbtest]
> [<d080d1cb>] usbtest_disconnect+0x1b/0x20 [usbtest]
I suspect you are triggering a bug in the input layer. Adding a few
debugging lines to the test driver, particularly in usbtest_delete, might
help pinpoint the bug.
> static int usbtest_probe(struct usb_interface *interface, const struct
> usb_device_id *id)
> {
> struct usb_device *udev = interface_to_usbdev(interface);
> struct usbtest *ut;
> int r;
>
> ut = kzalloc(sizeof (struct usbtest), GFP_KERNEL);
> if (!ut)
> return -ENOMEM;
>
> ut->udev = udev;
> usb_make_path(udev, ut->phys, sizeof(ut->phys));
> strlcat(ut->phys, "/input0", sizeof(ut->phys));
>
> strlcat(ut->name, "usbtest", sizeof(ut->name));
>
> r = usbtest_input_init(ut);
> if (r)
> goto error;
So you try to deregister the input device even if it failed to register?
Is that legal? (Although that's not what caused the oops in this case.)
>
> usb_set_intfdata(interface, ut);
In a real driver, you would probably want to do this before registering
the input device.
>
> return 0;
>
> error:
> usbtest_delete(ut);
>
> return r;
> }
Alan Stern
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