USB: yurex: Don't retry on unexpected errors
authorAlan Stern <stern@rowland.harvard.edu>
Tue, 17 Sep 2019 16:47:23 +0000 (12:47 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Fri, 4 Oct 2019 09:02:59 +0000 (11:02 +0200)
commit32a0721c6620b77504916dac0cea8ad497c4878a
tree9b5a494c20b969ad14890329dcbfbf44e1e34743
parentb2fa7baee744fde746c17bc1860b9c6f5c2eebb7
USB: yurex: Don't retry on unexpected errors

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