linux-kernel - [PATCH 4.4 063/117] usb: hub: do not clear BOS field during reset device

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Date:	Sun, 14 Feb 2016 14:21:40 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, "Du, Changbin" <changbin.du@...el.com>
Subject: [PATCH 4.4 063/117] usb: hub: do not clear BOS field during reset device

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Du, Changbin <changbin.du@...el.com>

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

Signed-off-by: Du, Changbin <changbin.du@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -5386,7 +5386,6 @@ static int usb_reset_and_verify_device(s
 	}

 	bos = udev->bos;
-	udev->bos = NULL;

 	for (i = 0; i < SET_CONFIG_TRIES; ++i) {

@@ -5479,8 +5478,11 @@ 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;

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