[PATCH] audit: grab a reference to context->pwd when it's cached

[Alexander Viro]

On Wed, Aug 15, 2012 at 06:13:33PM -0700, Peter Moody wrote:
> On certain systems, in certain pathalogical cases, current's cwd can
> be deleted while we're still processing a syscall. This should prevent
> the system from evicting the inode while we're still referencing it.
> 
> This seems to fix the bug I reported here:
> https://www.redhat.com/archives/linux-audit/2012-August/msg00017.html

Sigh...  The bug is real, but I really don't like the fix.  Among other
things, it's going to cause cacheline bouncing from hell and not everyone
runs with audit sensibly disabled...  Let me think for a while and see
if I can come up with something less unpleasant, OK?