Patch "usb: hub: do not clear BOS field during reset device" has been added to the 3.14-stable tree

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

usb: hub: do not clear BOS field during reset device

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-hub-do-not-clear-bos-field-during-reset-device.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Du, Changbin" <[email protected]>
Date: Mon, 18 Jan 2016 21:02:42 +0800
Subject: usb: hub: do not clear BOS field during reset device

From: Du, Changbin <[email protected]>

commit d8f00cd685f5c8e0def8593e520a7fef12c22407 upstream.

In function usb_reset_and_verify_device, the old BOS descriptor may still be used before allocating a new one. (usb_unlocked_disable_lpm function uses it under the situation that it fails to disable lpm.) So we cannot set the udev->bos to NULL before that, just keep what it was. It will be overwrite when allocating a new one.

Crash log:

BUG: unable to handle kernel NULL pointer dereference at
0000000000000010
IP: [<ffffffff8171f98d>] usb_enable_link_state+0x2d/0x2f0
Call Trace:
[<ffffffff8171ed5b>] ? usb_set_lpm_timeout+0x12b/0x140
[<ffffffff8171fcd1>] usb_enable_lpm+0x81/0xa0
[<ffffffff8171fdd8>] usb_disable_lpm+0xa8/0xc0
[<ffffffff8171fe1c>] usb_unlocked_disable_lpm+0x2c/0x50
[<ffffffff81723933>] usb_reset_and_verify_device+0xc3/0x710
[<ffffffff8172c4ed>] ? usb_sg_wait+0x13d/0x190
[<ffffffff81724743>] usb_reset_device+0x133/0x280
[<ffffffff8179ccd1>] usb_stor_port_reset+0x61/0x70
[<ffffffff8179cd68>] usb_stor_invoke_transport+0x88/0x520

---
 drivers/usb/core/hub.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

@@ -5225,7 +5225,6 @@ static int usb_reset_and_verify_device(s
 		usb_set_usb2_hardware_lpm(udev, 0);
 
 	bos = udev->bos;
-	udev->bos = NULL;
 
 	/* Disable LPM and LTM while we reset the device and reinstall the alt
 	 * settings.  Device-initiated LPM settings, and system exit latency

@@ -5334,8 +5333,11 @@ done:
 	usb_set_usb2_hardware_lpm(udev, 1);
 	usb_unlocked_enable_lpm(udev);
 	usb_enable_ltm(udev);
-	usb_release_bos_descriptor(udev);
-	udev->bos = bos;
+	/* release the new BOS descriptor allocated  by hub_port_init() */
+	if (udev->bos != bos) {
+		usb_release_bos_descriptor(udev);
+		udev->bos = bos;
+	}
 	return 0;
 
 re_enumerate:

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/usb-hub-do-not-clear-bos-field-during-reset-device.patch