Date: Thu, 5 Jul 2007 02:55:53 GMT From: Victor Liu <victor.liu@gmail.com> To: freebsd-gnats-submit@FreeBSD.org Subject: usb/114310: USB hub attachment panics kernel during libusb device scan Message-ID: <200707050255.l652trbP013836@www.freebsd.org> Resent-Message-ID: <200707050300.l6530Ao8025080@freefall.freebsd.org>
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>Number: 114310 >Category: usb >Synopsis: USB hub attachment panics kernel during libusb device scan >Confidential: no >Severity: critical >Priority: medium >Responsible: freebsd-usb >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Thu Jul 05 03:00:09 GMT 2007 >Closed-Date: >Last-Modified: >Originator: Victor Liu >Release: 5.4-RELEASE >Organization: Fastsoft >Environment: FreeBSD xxxxxxxxxxxxxxxxxxxxxxxxx 5.4-RELEASE FreeBSD 5.4-RELEASE #44: Mon Jul 2 18:25:07 PDT 2007 root@xxxxxxxxxxxxxxxxxxxxxxxxx:/usr/src/sys/i386/compile/xxxxxxxxxxxxx i386 >Description: When attaching a USB hub (anything from a generic DLink to a keyboard with integrated hub) while a userspace libusb query is going on, the kernel panics (trap 12, fault virtual address = 0xdeadc0e6) at usbd_device_fillinfo:1350; p->device is 0xdeadc0de. I have experimented several times, I think the cause is during hub attachment, there is a tsleep when waiting for power to settle (uhub.c:288). In this time, libusb's usb_find_devices happens to request an ioctl for a device exploration. At this point, the port structures of the hub are not yet initialized. I have a temporary fix that just initializes p->device to NULL before the sleep, but this doesn't solve a similar problem exists during hub detachment (which I haven't been able to narrow it down much further). >How-To-Repeat: Run a program that continuously polls for USB devices using libusb's usb_find_devices(), while attaching a USB hub. This won't cause it to crash everytime, but it is likely that out of 20 attachments, there will be at least one panic. A piece of code along the lines of while(1){ DPRINTF(("before usb_init\n")); usb_init(); DPRINTF(("before usb_find_busses\n")); usb_find_busses(); DPRINTF(("before usb_find_devices\n")); usb_find_devices(); } should do the trick of producing something like the log. >Fix: Proposed patch (only a hackish fix for the attachment problem): @@ -284,6 +284,15 @@ goto bad; } + // Fixes crash on hub attachment + // Need to init device to NULL before delay sleep; + // otherwise exploration could hit an uninit'd port + for (p = 0; p < nports; p++) { + struct usbd_port *up = &hub->ports[p]; + up->device = NULL; + } + // end changes + /* Wait with power off for a while. */ usbd_delay_ms(dev, USB_POWER_DOWN_TIME); >Release-Note: >Audit-Trail: >Unformatted:
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