2.6.32.55.15.svcrpc-fix-double-free-on-shutdown-of-nfsd-after-changing-pool-mode.patch

From 61c8504c428edcebf23b97775a129c5b393a302b Mon Sep 17 00:00:00 2001
From: "J. Bruce Fields" <bfields@redhat.com>
Date: Thu, 22 Dec 2011 18:22:49 -0700
Subject: svcrpc: fix double-free on shutdown of nfsd after changing pool mode

From: "J. Bruce Fields" <bfields@redhat.com>

commit 61c8504c428edcebf23b97775a129c5b393a302b upstream.

The pool_to and to_pool fields of the global svc_pool_map are freed on
shutdown, but are initialized in nfsd startup only in the
SVC_POOL_PERCPU and SVC_POOL_PERNODE cases.

They *are* initialized to zero on kernel startup.  So as long as you use
only SVC_POOL_GLOBAL (the default), this will never be a problem.

You're also OK if you only ever use SVC_POOL_PERCPU or SVC_POOL_PERNODE.

However, the following sequence events leads to a double-free:

	1. set SVC_POOL_PERCPU or SVC_POOL_PERNODE
	2. start nfsd: both fields are initialized.
	3. shutdown nfsd: both fields are freed.
	4. set SVC_POOL_GLOBAL
	5. start nfsd: the fields are left untouched.
	6. shutdown nfsd: now we try to free them again.

Step 4 is actually unnecessary, since (for some bizarre reason), nfsd
automatically resets the pool mode to SVC_POOL_GLOBAL on shutdown.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 net/sunrpc/svc.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -166,6 +166,7 @@ svc_pool_map_alloc_arrays(struct svc_poo
 
 fail_free:
 	kfree(m->to_pool);
+	m->to_pool = NULL;
 fail:
 	return -ENOMEM;
 }
@@ -286,7 +287,9 @@ svc_pool_map_put(void)
 	if (!--m->count) {
 		m->mode = SVC_POOL_DEFAULT;
 		kfree(m->to_pool);
+		m->to_pool = NULL;
 		kfree(m->pool_to);
+		m->pool_to = NULL;
 		m->npools = 0;
 	}