[PATCH 3.16 020/136] USB: yurex: Don't retry on unexpected errors

Ben Hutchings
2019-12-17T00:59:51Z

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>

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
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",