On Tue, Feb 07, 2017 at 11:56:51AM +0000, David Laight wrote: > From: Greg KH > > Sent: 07 February 2017 10:52 > > To: Petko Manolov > > Cc: Ben Hutchings; David Laight; netdev@vger.kernel.org; > > linux-...@vger.kernel.org > > Subject: Re: [PATCH net 2/4] rtl8150: Use heap buffers for all register > > access > > > > On Tue, Feb 07, 2017 at 12:34:52PM +0200, Petko Manolov wrote: > > > On 17-02-06 16:25:20, Ben Hutchings wrote: > > > > On Mon, Feb 06, 2017 at 04:09:18PM +0000, David Laight wrote: > > > > > From: Ben Hutchings > > > > [...] > > > > > > + ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0), > > > > > > + RTL8150_REQ_GET_REGS, RTL8150_REQT_READ, > > > > > > + indx, 0, buf, size, 500); > > > > > > + if (ret > 0 && ret <= size) > > > > > > + memcpy(data, buf, ret); > > > > > > > > > > If ret > size something is horridly wrong. > > > > > Silently not updating the callers buffer at all cannot be right. > > > > > > > > Yes, it seems strange to check this. I originally wrote this as ret > > > > > 0, but then I checked the usbnet core and found __usbnet_read_cmd() > > > > has the second comparison as well. > > > > > > > > > > + kfree(buf); > > > > > > + return ret; > > > > > > Since we return what usb_control_msg() told us to return i assume the > > > error code > > > will be available to anybody who cares. > > > > > > > > I can't help feeling that it would be better to add a wrapper to > > > > > usb_control_msg() that does the kmalloc() and memcpy()s and > > > > > drop that into all the call sites. > > > > > > > > It might be. Right now I'm trying to patch up a bunch of regressions > > > > rather > > > > than argue over an API change. > > > > > > Right, first thing first. > > > > > > I am in favor of changing the API, but this should not happen in the > > > stable > > > releases. I hope Greg will make up his mind and let us know. > > > > make up my mind about what? These are bugs, they should be fixed, I'm > > not taking a total api change at this point in time, sorry. > > Adding a usb_control_msg_with_malloc() wrapper is a smaller change than those > proposed. The smaller churn probably makes back porting other changes easier. > > Given the nature of this problem, and how common it seems to be, > it is almost worth renaming usb_control_msg() itself so that all the > callers are properly audited.
As this is something that we have been auditing for a decade now, I don't think you will find all that many instances :) But for now, fixes like this are fine, if someone wants to tackle the larger issue here, with a new api function, that would be great. thanks, greg k-h
