On Fri, Apr 15, 2022 at 03:33:23AM +0000, Michael Kelley (LINUX) wrote: > From: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx> Sent: Wednesday, April 13, 2022 1:48 PM > > > > The function returns NULL if the ring buffer has no enough space > > available for a packet descriptor. The ring buffer's write_index > > The first sentence wording is a bit scrambled. I think you mean the > ring buffer doesn't contain enough readable bytes to constitute a > packet descriptor. Indeed, replaced with your working. > > is in memory which is shared with the Hyper-V host, its value is > > thus subject to being changed at any time. > > This second sentence is true, but I'm not making the connection > with the code change below. Evidently, there is some previous > check made to ensure that enough bytes are available to be > received when hvs_stream_dequeue() is called, so we assumed that > NULL could never be returned? I looked but didn't find such a check, > so maybe I didn't look carefully enough. But now we are assuming > that Hyper-V might have invalidated that previous check by > subsequently changing the write_index in a bogus way? So now, NULL > could be returned when previously we assumed it couldn't. I think you're looking for hvs_stream_has_data(). (Previous checks apart, hvs_stream_dequeue() will "dereference" the pointer so...) Thanks, Andrea
