[PATCH 5.8 05/85] Revert "usbip: Implement a match function to fix usbip"

[Greg Kroah-Hartman]

From: M. Vefa Bicakci <m.v.b@xxxxxxxxxx>

commit d6407613c1e2ef90213dee388aa16b6e1bd08cbc upstream.

This commit reverts commit 7a2f2974f265 ("usbip: Implement a match
function to fix usbip").

In summary, commit d5643d2249b2 ("USB: Fix device driver race")
inadvertently broke usbip functionality, which I resolved in an incorrect
manner by introducing a match function to usbip, usbip_match(), that
unconditionally returns true.

However, the usbip_match function, as is, causes usbip to take over
virtual devices used by syzkaller for USB fuzzing, which is a regression
reported by Andrey Konovalov.

Furthermore, in conjunction with the fix of another bug, handled by another
patch titled "usbcore/driver: Fix specific driver selection" in this patch
set, the usbip_match function causes unexpected USB subsystem behaviour
when the usbip_host driver is loaded. The unexpected behaviour can be
qualified as follows:
- If commit 41160802ab8e ("USB: Simplify USB ID table match") is included
  in the kernel, then all USB devices are bound to the usbip_host
  driver, which appears to the user as if all USB devices were
  disconnected.
- If the same commit (41160802ab8e) is not in the kernel (as is the case
  with v5.8.10) then all USB devices are re-probed and re-bound to their
  original device drivers, which appears to the user as a disconnection
  and re-connection of USB devices.

Please note that this commit will make usbip non-operational again,
until yet another patch in this patch set is merged, titled
"usbcore/driver: Accommodate usbip".

Cc: <stable@xxxxxxxxxxxxxxx> # 5.8: 41160802ab8e: USB: Simplify USB ID table match
Cc: <stable@xxxxxxxxxxxxxxx> # 5.8
Cc: Bastien Nocera <hadess@xxxxxxxxxx>
Cc: Valentina Manea <valentina.manea.m@xxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Cc: <syzkaller@xxxxxxxxxxxxxxxx>
Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Acked-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: M. Vefa Bicakci <m.v.b@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200922110703.720960-2-m.v.b@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/usbip/stub_dev.c |    6 ------
 1 file changed, 6 deletions(-)

--- a/drivers/usb/usbip/stub_dev.c
+++ b/drivers/usb/usbip/stub_dev.c
@@ -461,11 +461,6 @@ static void stub_disconnect(struct usb_d
 	return;
 }
 
-static bool usbip_match(struct usb_device *udev)
-{
-	return true;
-}
-
 #ifdef CONFIG_PM
 
 /* These functions need usb_port_suspend and usb_port_resume,
@@ -491,7 +486,6 @@ struct usb_device_driver stub_driver = {
 	.name		= "usbip-host",
 	.probe		= stub_probe,
 	.disconnect	= stub_disconnect,
-	.match		= usbip_match,
 #ifdef CONFIG_PM
 	.suspend	= stub_suspend,
 	.resume		= stub_resume,