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authorKurt Garloff <kurt@garloff.de>2013-09-24 14:13:48 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-09-25 17:30:39 -0700
commit831abf76643555a99b80a3b54adfa7e4fa0a3259 (patch)
treef7107f3fc8a2c18af0f072c1a4393e4d892e98c4 /drivers/usb
parent2c740336159d9785ae81e8f9d6ba1a6b922723c9 (diff)
usb/core/devio.c: Don't reject control message to endpoint with wrong direction bit
Trying to read data from the Pegasus Technologies NoteTaker (0e20:0101) [1] with the Windows App (EasyNote) works natively but fails when Windows is running under KVM (and the USB device handed to KVM). The reason is a USB control message usb 4-2.2: control urb: bRequestType=22 bRequest=09 wValue=0200 wIndex=0001 wLength=0008 This goes to endpoint address 0x01 (wIndex); however, endpoint address 0x01 does not exist. There is an endpoint 0x81 though (same number, but other direction); the app may have meant that endpoint instead. The kernel thus rejects the IO and thus we see the failure. Apparently, Linux is more strict here than Windows ... we can't change the Win app easily, so that's a problem. It seems that the Win app/driver is buggy here and the driver does not behave fully according to the USB HID class spec that it claims to belong to. The device seems to happily deal with that though (and seems to not really care about this value much). So the question is whether the Linux kernel should filter here. Rejecting has the risk that somewhat non-compliant userspace apps/ drivers (most likely in a virtual machine) are prevented from working. Not rejecting has the risk of confusing an overly sensitive device with such a transfer. Given the fact that Windows does not filter it makes this risk rather small though. The patch makes the kernel more tolerant: If the endpoint address in wIndex does not exist, but an endpoint with toggled direction bit does, it will let the transfer through. (It does NOT change the message.) With attached patch, the app in Windows in KVM works. usb 4-2.2: check_ctrlrecip: process 13073 (qemu-kvm) requesting ep 01 but needs 81 I suspect this will mostly affect apps in virtual environments; as on Linux the apps would have been adapted to the stricter handling of the kernel. I have done that for mine[2]. [1] http://www.pegatech.com/ [2] https://sourceforge.net/projects/notetakerpen/ Signed-off-by: Kurt Garloff <kurt@garloff.de> Acked-by: Alan Stern <stern@rowland.harvard.edu> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb')
-rw-r--r--drivers/usb/core/devio.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 737e3c19967..71dc5d768fa 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -742,6 +742,22 @@ static int check_ctrlrecip(struct dev_state *ps, unsigned int requesttype,
if ((index & ~USB_DIR_IN) == 0)
return 0;
ret = findintfep(ps->dev, index);
+ if (ret < 0) {
+ /*
+ * Some not fully compliant Win apps seem to get
+ * index wrong and have the endpoint number here
+ * rather than the endpoint address (with the
+ * correct direction). Win does let this through,
+ * so we'll not reject it here but leave it to
+ * the device to not break KVM. But we warn.
+ */
+ ret = findintfep(ps->dev, index ^ 0x80);
+ if (ret >= 0)
+ dev_info(&ps->dev->dev,
+ "%s: process %i (%s) requesting ep %02x but needs %02x\n",
+ __func__, task_pid_nr(current),
+ current->comm, index, index ^ 0x80);
+ }
if (ret >= 0)
ret = checkintf(ps, ret);
break;