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
Signed-off-by: Alan Stern <firstname.lastname@example.org>
Acked-by: Felipe Balbi <email@example.com>
Signed-off-by: Greg Kroah-Hartman <firstname.lastname@example.org>