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

[Andrew Morton <akpm@linux-foundation.org>]

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.