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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Alan Stern <stern@rowland.harvard.edu>,
        Tomoki Sekiyama <tomoki.sekiyama@gmail.com>,
        syzbot+b24d736f18a1541ad550@syzkaller.appspotmail.com
Subject: [PATCH 4.9 38/92] USB: yurex: Dont retry on unexpected errors
Date:   Wed, 16 Oct 2019 14:50:11 -0700
Message-Id: <20191016214829.499578660@linuxfoundation.org>
In-Reply-To: <20191016214759.600329427@linuxfoundation.org>
References: <20191016214759.600329427@linuxfoundation.org>
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From: Alan Stern <stern@rowland.harvard.edu>

commit 32a0721c6620b77504916dac0cea8ad497c4878a upstream.

According to Greg KH, it has been generally agreed that when a USB
driver encounters an unknown error (or one it can't handle directly),
it should just give up instead of going into a potentially infinite
retry loop.

The three codes -EPROTO, -EILSEQ, and -ETIME fall into this category.
They can be caused by bus errors such as packet loss or corruption,
attempting to communicate with a disconnected device, or by malicious
firmware.  Nowadays the extent of packet loss or corruption is
negligible, so it should be safe for a driver to give up whenever one
of these errors occurs.

Although the yurex driver handles -EILSEQ errors in this way, it
doesn't do the same for -EPROTO (as discovered by the syzbot fuzzer)
or other unrecognized errors.  This patch adjusts the driver so that
it doesn't log an error message for -EPROTO or -ETIME, and it doesn't
retry after any errors.

Reported-and-tested-by: syzbot+b24d736f18a1541ad550@syzkaller.appspotmail.com
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Tomoki Sekiyama <tomoki.sekiyama@gmail.com>
CC: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1909171245410.1590-100000@iolanthe.rowland.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/misc/yurex.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/usb/misc/yurex.c
+++ b/drivers/usb/misc/yurex.c
@@ -136,6 +136,7 @@ static void yurex_interrupt(struct urb *
 	switch (status) {
 	case 0: /*success*/
 		break;
+	/* The device is terminated or messed up, give up */
 	case -EOVERFLOW:
 		dev_err(&dev->interface->dev,
 			"%s - overflow with length %d, actual length is %d\n",
@@ -144,12 +145,13 @@ static void yurex_interrupt(struct urb *
 	case -ENOENT:
 	case -ESHUTDOWN:
 	case -EILSEQ:
-		/* The device is terminated, clean up */
+	case -EPROTO:
+	case -ETIME:
 		return;
 	default:
 		dev_err(&dev->interface->dev,
 			"%s - unknown status received: %d\n", __func__, status);
-		goto exit;
+		return;
 	}
 
 	/* handle received message */
@@ -181,7 +183,6 @@ static void yurex_interrupt(struct urb *
 		break;
 	}
 
-exit:
 	retval = usb_submit_urb(dev->urb, GFP_ATOMIC);
 	if (retval) {
 		dev_err(&dev->interface->dev, "%s - usb_submit_urb failed: %d\n",