From d1c188d330ca33cc35d1590441ba276f31144299 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Mon, 28 Oct 2019 10:54:26 -0400 Subject: [PATCH] USB: gadget: Reject endpoints with 0 maxpacket value commit 54f83b8c8ea9b22082a496deadf90447a326954e upstream. 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 Reported-and-tested-by: syzbot+8ab8bf161038a8768553@syzkaller.appspotmail.com CC: Acked-by: Felipe Balbi Link: https://lore.kernel.org/r/Pine.LNX.4.44L0.1910281052370.1485-100000@iolanthe.rowland.org Signed-off-by: Greg Kroah-Hartman --- 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 af88b48..aa31d36 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; -- 2.7.4