patch "Revert "usbip: Implement a match function to fix usbip"" added to usb-linus

This is a note to let you know that I've just added the patch titled

Revert "usbip: Implement a match function to fix usbip"

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From d6407613c1e2ef90213dee388aa16b6e1bd08cbc Mon Sep 17 00:00:00 2001
From: "M. Vefa Bicakci" <[email protected]>
Date: Tue, 22 Sep 2020 14:07:00 +0300
Subject: Revert "usbip: Implement a match function to fix usbip"

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".

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

index 9d7d642022d1..2305d425e6c9 100644
@@ -461,11 +461,6 @@ static void stub_disconnect(struct usb_device *udev)
 	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,

2.28.0