linux-kernel - Re: [PATCH AUTOSEL 5.13 06/21] USB: core: Fix incorrect pipe calculation in do_proc

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Date:   Tue, 27 Jul 2021 14:54:08 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Alan Stern <stern@...land.harvard.edu>,
        syzbot+72af3105289dcb4c055b@...kaller.appspotmail.com,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.13 06/21] USB: core: Fix incorrect pipe
 calculation in do_proc_control()

On Tue, Jul 27, 2021 at 03:28:20PM +0200, Greg Kroah-Hartman wrote:
>On Tue, Jul 27, 2021 at 09:18:53AM -0400, Sasha Levin wrote:
>> From: Alan Stern <stern@...land.harvard.edu>
>>
>> [ Upstream commit b0863f1927323110e3d0d69f6adb6a91018a9a3c ]
>>
>> When the user submits a control URB via usbfs, the user supplies the
>> bRequestType value and the kernel uses it to compute the pipe value.
>> However, do_proc_control() performs this computation incorrectly in
>> the case where the bRequestType direction bit is set to USB_DIR_IN and
>> the URB's transfer length is 0: The pipe's direction is also set to IN
>> but it should be OUT, which is the direction the actual transfer will
>> use regardless of bRequestType.
>>
>> Commit 5cc59c418fde ("USB: core: WARN if pipe direction != setup
>> packet direction") added a check to compare the direction bit in the
>> pipe value to a control URB's actual direction and to WARN if they are
>> different.  This can be triggered by the incorrect computation
>> mentioned above, as found by syzbot.
>>
>> This patch fixes the computation, thus avoiding the WARNing.
>>
>> Reported-and-tested-by: syzbot+72af3105289dcb4c055b@...kaller.appspotmail.com
>> Signed-off-by: Alan Stern <stern@...land.harvard.edu>
>> Link: https://lore.kernel.org/r/20210712185436.GB326369@rowland.harvard.edu
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  drivers/usb/core/devio.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
>> index 2218941d35a3..73b60f013b20 100644
>> --- a/drivers/usb/core/devio.c
>> +++ b/drivers/usb/core/devio.c
>> @@ -1133,7 +1133,7 @@ static int do_proc_control(struct usb_dev_state *ps,
>>  		"wIndex=%04x wLength=%04x\n",
>>  		ctrl->bRequestType, ctrl->bRequest, ctrl->wValue,
>>  		ctrl->wIndex, ctrl->wLength);
>> -	if (ctrl->bRequestType & 0x80) {
>> +	if ((ctrl->bRequestType & USB_DIR_IN) && ctrl->wLength) {
>>  		pipe = usb_rcvctrlpipe(dev, 0);
>>  		snoop_urb(dev, NULL, pipe, ctrl->wLength, tmo, SUBMIT, NULL, 0);
>>
>> --
>> 2.30.2
>>
>
>This is not needed in any kernel that does not also have 5cc59c418fde
>("USB: core: WARN if pipe direction != setup packet direction"), which
>showed up in 5.14-rc1, so please drop this from all of the AUTOSEL
>trees.

Will do, thanks!

-- 
Thanks,
Sasha