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From: Alan Stern <stern@rowland.harvard.edu>
To: syzbot <syzbot+9b57a46bf1801ce2a2ca@syzkaller.appspotmail.com>
Cc: benjamin.tissoires@redhat.com, jikos@kernel.org,
	linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-usb@vger.kernel.org, mkubecek@suse.cz,
	syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] WARNING in hid_submit_ctrl/usb_submit_urb
Date: Thu, 19 Aug 2021 15:53:00 -0400	[thread overview]
Message-ID: <20210819195300.GA8613@rowland.harvard.edu> (raw)
In-Reply-To: <00000000000009e24705c9ecf9b3@google.com>

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;

  reply	other threads:[~2021-08-19 19:53 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-18 15:46 syzbot
2021-08-18  9:14 ` syzbot
2021-08-18 18:49   ` Alan Stern
2021-08-18 20:13     ` syzbot
2021-08-19 15:26       ` Alan Stern
2021-08-19 17:35         ` syzbot
2021-08-19 19:53           ` Alan Stern [this message]
2021-08-20  0:40             ` syzbot
2021-08-20 14:06               ` Alan Stern
2021-08-24 11:53                 ` Jiri Kosina
2021-08-24 12:34                   ` Benjamin Tissoires
2021-08-31  9:51                   ` Benjamin Tissoires
2021-08-31 13:34                     ` Alan Stern
2021-08-31 19:53                       ` Jiri Kosina
2021-09-01 15:38                     ` Alan Stern
2021-09-01 15:51                       ` Michal Kubecek
2021-08-24 11:50             ` Michal Kubecek
2021-08-30 19:22             ` Oleksandr Natalenko
2021-08-18 19:01   ` Alan Stern
2021-08-18 19:39 ` syzbot

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