This is a note to let you know that I've just added the patch titled

USB: gadget: Reject endpoints with 0 maxpacket value

to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 54f83b8c8ea9b22082a496deadf90447a326954e Mon Sep 17 00:00:00 2001

From: Alan Stern stern@rowland.harvard.edu Date: Mon, 28 Oct 2019 10:54:26 -0400 Subject: USB: gadget: Reject endpoints with 0 maxpacket value

Endpoints with a maxpacket length of 0 are probably useless. They can't transfer any data, and it's not at all unlikely that a UDC will crash or hang when trying to handle a non-zero-length usb_request for such an endpoint. Indeed, dummy-hcd gets a divide error when trying to calculate the remainder of a transfer length by the maxpacket value, as discovered by the syzbot fuzzer.

Currently the gadget core does not check for endpoints having a maxpacket value of 0. This patch adds a check to usb_ep_enable(), preventing such endpoints from being used.

As far as I know, none of the gadget drivers in the kernel tries to create an endpoint with maxpacket = 0, but until now there has been nothing to prevent userspace programs under gadgetfs or configfs from doing it.

Signed-off-by: Alan Stern stern@rowland.harvard.edu Reported-and-tested-by: syzbot+8ab8bf161038a8768553@syzkaller.appspotmail.com CC: stable@vger.kernel.org Acked-by: Felipe Balbi balbi@kernel.org

Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1910281052370.1485-100000@iolanthe... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/gadget/udc/core.c | 11 +++++++++++ 1 file changed, 11 insertions(+)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c index 92af8dc98c3d..51fa614b4079 100644 --- a/drivers/usb/gadget/udc/core.c +++ b/drivers/usb/gadget/udc/core.c @@ -98,6 +98,17 @@ int usb_ep_enable(struct usb_ep *ep) if (ep->enabled) goto out;

+ /* UDC drivers can't handle endpoints with maxpacket size 0 */ + if (usb_endpoint_maxp(ep->desc) == 0) { + /* + * We should log an error message here, but we can't call + * dev_err() because there's no way to find the gadget + * given only ep. + */ + ret = -EINVAL; + goto out; + } + ret = ep->ops->enable(ep, ep->desc); if (ret) goto out;