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

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Message-Id: <1453122162-5054-1-git-send-email-changbin.du@intel.com>
Date:	Mon, 18 Jan 2016 21:02:42 +0800
From:	changbin.du@...el.com
To:	gregkh@...uxfoundation.org
Cc:	stern@...land.harvard.edum, baolu.lu@...ux.intel.com, balbi@...com,
	chasemetzger15@...il.com, kborer@...il.com, mjg59@...eos.com,
	jun.li@...escale.com, Robert.Schlabbach@....net,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Du, Changbin" <changbin.du@...el.com>
Subject: [PATCH] usb: hub: do not clear BOS field during reset device

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

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

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 51b43691..350dcd9 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -5401,7 +5401,6 @@ static int usb_reset_and_verify_device(struct usb_device *udev)
 	}

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

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

@@ -5494,8 +5493,11 @@ 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:
-- 
2.5.0