linux-kernel - Re: [syzbot] WARNING in hid_submit_ctrl/usb_submit

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Date:   Mon, 30 Aug 2021 21:22:39 +0200
From:   Oleksandr Natalenko <oleksandr@...alenko.name>
To:     syzbot <syzbot+9b57a46bf1801ce2a2ca@...kaller.appspotmail.com>,
        Alan Stern <stern@...land.harvard.edu>
Cc:     benjamin.tissoires@...hat.com, jikos@...nel.org,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, mkubecek@...e.cz,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] WARNING in hid_submit_ctrl/usb_submit_urb

Hello.

On čtvrtek 19. srpna 2021 21:53:00 CEST Alan Stern wrote:
> On Thu, Aug 19, 2021 at 10:35:11AM -0700, syzbot wrote:
> > Hello,
> > 
> > syzbot has tested the proposed patch but the reproducer is still
> > triggering an issue: WARNING in hid_submit_ctrl/usb_submit_urb
> > 
> > cm6533_jd 0003:0D8C:0022.0001: submit_ctrl: maxpacket 64 len 0 padlen 0
> > ------------[ cut here ]------------
> > usb 1-1: BOGUS control dir, pipe 80000280 doesn't match bRequestType a1
> 
> Ah.   The padding code doesn't add anything if the length is
> already a multiple of the maxpacket value, and of course 0 is such
> a multiple.
> 
> The following simplified variant of Michal's patch should fix the
> problem.
> 
> Alan Stern
> 
> #syz test:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> 794c7931a242
> 
> Index: usb-devel/drivers/hid/usbhid/hid-core.c
> ===================================================================
> --- usb-devel.orig/drivers/hid/usbhid/hid-core.c
> +++ usb-devel/drivers/hid/usbhid/hid-core.c
> @@ -377,27 +377,23 @@ static int hid_submit_ctrl(struct hid_de
>  	len = hid_report_len(report);
>  	if (dir == USB_DIR_OUT) {
>  		usbhid->urbctrl->pipe = usb_sndctrlpipe(hid_to_usb_dev(hid), 
0);
> -		usbhid->urbctrl->transfer_buffer_length = len;
>  		if (raw_report) {
>  			memcpy(usbhid->ctrlbuf, raw_report, len);
>  			kfree(raw_report);
>  			usbhid->ctrl[usbhid->ctrltail].raw_report = NULL;
>  		}
>  	} else {
> -		int maxpacket, padlen;
> +		int maxpacket;
> 
>  		usbhid->urbctrl->pipe = usb_rcvctrlpipe(hid_to_usb_dev(hid), 
0);
>  		maxpacket = usb_maxpacket(hid_to_usb_dev(hid),
>  					  usbhid->urbctrl->pipe, 0);
> -		if (maxpacket > 0) {
> -			padlen = DIV_ROUND_UP(len, maxpacket);
> -			padlen *= maxpacket;
> -			if (padlen > usbhid->bufsize)
> -				padlen = usbhid->bufsize;
> -		} else
> -			padlen = 0;
> -		usbhid->urbctrl->transfer_buffer_length = padlen;
> +		len += (len == 0);	/* Don't allow 0-length reports */
> +		len = round_up(len, maxpacket);
> +		if (len > usbhid->bufsize)
> +			len = usbhid->bufsize;
>  	}
> +	usbhid->urbctrl->transfer_buffer_length = len;
>  	usbhid->urbctrl->dev = hid_to_usb_dev(hid);
> 
>  	usbhid->cr->bRequestType = USB_TYPE_CLASS | USB_RECIP_INTERFACE | dir;

I've tried both Michal's patch as well as this one, and both work for me, 
hence feel free to add this:

Tested-by: Oleksandr Natalenko <oleksandr@...alenko.name>

once the fix is submitted.

Thanks!

-- 
Oleksandr Natalenko (post-factum)