From 15cdeadaa5d76009e20c7792aed69f5a73808f97 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Tue, 21 Sep 2010 21:17:32 +0000
Subject: [PATCH] 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>
---
net/netfilter/nf_conntrack_extend.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
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;