Re: [PATCH] NLM: hold BKL when clearing global lockd task and serv vars

["J. Bruce Fields" <bfields@fieldses.org>]

On Mon, Apr 07, 2008 at 12:45:01PM -0400, Christoph Hellwig wrote:
> On Mon, Apr 07, 2008 at 09:38:34AM -0400, Jeff Layton wrote:
> > The global task and serv pointers for lockd are normally protected by
> > the nlmsvc_mutex. The exception is when the lockd exits abnormally. When
> > this occurs, these variables are cleared without any locking.
> 
> Shouldn't we get rid of the case where it exits abnormally instead?

I tried to figure out when this could actually occur (when can
svc_recv() return an error other than -EINTR or -EAGAIN?), and got lost
in sock_recvmsg():

	- svc_recv() itself returns only -EAGAIN or the return from
	  ->xpo_recvfrom().
	- the only xpo_recvfrom() that's interesting is
	  svc_tcp_recvfrom(), which can return the error it gets from
	  svc_recvfrom(), which can return the error from
	  kernel_recvmsg(), which gets its return from sock_recvmsg().

Since __sock_recvmsg() has a security hook, it looks like we can end up
with an -EACCES from selinux?

So one case would be selinux deciding we weren't allowed to receive
packets from this socket.  Huh.

--b.