From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 21 Sep 2010 21:17:32 +0000 (+0000)
Subject: netfilter: fix a race in nf_ct_ext_create()
X-Git-Tag: Ubuntu-goldfish-3.4.0-4.27~5654^2~32
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=15cdeadaa5d76009e20c7792aed69f5a73808f97;p=mirror_ubuntu-zesty-kernel.git

netfilter: fix a race in nf_ct_ext_create()

As soon as rcu_read_unlock() is called, there is no guarantee current
thread can safely derefence t pointer, rcu protected.

Fix is to copy t->alloc_size in a temporary variable.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/netfilter/nf_conntrack_extend.c b/net/netfilter/nf_conntrack_extend.c
index 7dcf7a404190..8d9e4c949b96 100644
--- a/net/netfilter/nf_conntrack_extend.c
+++ b/net/netfilter/nf_conntrack_extend.c
@@ -48,15 +48,17 @@ nf_ct_ext_create(struct nf_ct_ext **ext, enum nf_ct_ext_id id, gfp_t gfp)
 {
 	unsigned int off, len;
 	struct nf_ct_ext_type *t;
+	size_t alloc_size;
 
 	rcu_read_lock();
 	t = rcu_dereference(nf_ct_ext_types[id]);
 	BUG_ON(t == NULL);
 	off = ALIGN(sizeof(struct nf_ct_ext), t->align);
 	len = off + t->len;
+	alloc_size = t->alloc_size;
 	rcu_read_unlock();
 
-	*ext = kzalloc(t->alloc_size, gfp);
+	*ext = kzalloc(alloc_size, gfp);
 	if (!*ext)
 		return NULL;