nullfs and named pipes.

[Robert Watson]

On Mon, 19 Feb 2007, Robert Watson wrote:

> On Sun, 18 Feb 2007, Josef Karthauser wrote:
>
> Well, the worry would be that you would be replacing a clean error on 
> failure with an occasional panic, the normal symptom of a race condition.
>
> I think I'm alright with the VFIFO case above, but I'm quite uncomfortable 
> with the VSOCK case.  In particular, I suspect that if the socket is closed, 
> v_un will be reset in the lower layer, but continue to be a stale pointer in 
> the upper layer, leading to accessing free'd or re-allocated kernel memory 
> resulting in much badness.  I've noticed tested this, but you might give it 
> a try and see what happens.

Bad typing day.  Should read "not tested this".  In any case, you get the 
idea: the problem here is a potential coherency issue on contents of v_un 
between the two file system layers.

Robert N M Watson
Computer Laboratory
University of Cambridge