Re: [PATCH] knfsd: Fix a race in closing NFSd connections.

Andrew Morton
2007-02-07T01:53:13Z

On Wed, 7 Feb 2007 11:10:26 +1100
NeilBrown <neilb@suse.de> wrote:

> If you lose this race, it can iput a socket inode twice and you
> get a BUG in fs/inode.c
>
> When I added the option for user-space to close a socket,
> I added some cruft to svc_delete_socket so that I could call
> that function when closing a socket per user-space request.
>
> This was the wrong thing to do. I should have just set SK_CLOSE
> and let normal mechanisms do the work.
>
> Not only wrong, but buggy. The locking is all wrong and it openned
> up a race where-by a socket could be closed twice.
>
> So this patch:
> Introduces svc_close_socket which sets SK_CLOSE then either leave
> the close up to a thread, or calls svc_delete_socket if it can
> get SK_BUSY.
>
> Adds a bias to sk_busy which is removed when SK_DEAD is set,
> This avoid races around shutting down the socket.
>
> Changes several 'spin_lock' to 'spin_lock_bh' where the _bh
> was missing.
>

This patch assumes the presence of
knfsd-sunrpc-allow-creating-an-rpc-service-without-registering-with-portmapper.patch which
obviously isn't appropriate for -stable.

Please confirm that the patch which I merged is still OK, thanks.