[PATCH] knfsd: fix a race in closing NFSd connections

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.

Bugzilla-url: http://bugzilla.kernel.org/show_bug.cgi?id=7916

Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 4c161121111..c1f878131ac 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -386,7 +386,7 @@ svc_destroy(struct svc_serv *serv)
 		svsk = list_entry(serv->sv_tempsocks.next,
 				  struct svc_sock,
 				  sk_list);
-		svc_delete_socket(svsk);
+		svc_close_socket(svsk);
 	}
 	if (serv->sv_shutdown)
 		serv->sv_shutdown(serv);
@@ -395,7 +395,7 @@ svc_destroy(struct svc_serv *serv)
 		svsk = list_entry(serv->sv_permsocks.next,
 				  struct svc_sock,
 				  sk_list);
-		svc_delete_socket(svsk);
+		svc_close_socket(svsk);
 	}
 	
 	cache_clean_deferred(serv);