patch "usb: hub: do not clear BOS field during reset device" added to usb-linus

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

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(-)

index 51b436918f78..350dcd9af5d8 100644
@@ -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:

2.7.0