From: Hans de Goede Date: Sat, 17 Nov 2012 11:11:50 +0000 (+0100) Subject: uhci: Don't allow the guest to set port-enabled when there is no dev connected X-Git-Tag: qemu-xen-4.3.0-rc1~17^2~57^2~5 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=1cbdde909f70fd15ff85f068a6318b73865c7fa3;p=qemu-upstream-4.3-testing.git uhci: Don't allow the guest to set port-enabled when there is no dev connected It is possible for device disconnect and the guest trying to reset the port (because of USB xact errors prior to the disconnect getting signaled) to race, when we hit this race, the guest will write the port-control register with its pre-disconnect value + the reset bit set, after which we have a disconnected device with its port-enabled bit set in its port-control register, which is no good :) Signed-off-by: Hans de Goede Signed-off-by: Gerd Hoffmann --- diff --git a/hw/usb/hcd-uhci.c b/hw/usb/hcd-uhci.c index ef326330d..078be2ad6 100644 --- a/hw/usb/hcd-uhci.c +++ b/hw/usb/hcd-uhci.c @@ -556,6 +556,10 @@ static void uhci_ioport_writew(void *opaque, uint32_t addr, uint32_t val) } } port->ctrl &= UHCI_PORT_READ_ONLY; + /* enabled may only be set if a device is connected */ + if (!(port->ctrl & UHCI_PORT_CCS)) { + val &= ~UHCI_PORT_EN; + } port->ctrl |= (val & ~UHCI_PORT_READ_ONLY); /* some bits are reset when a '1' is written to them */ port->ctrl &= ~(val & UHCI_PORT_WRITE_CLEAR);