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netfilter: fix a race in nf_ct_ext_create()

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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>
This commit is contained in:
Eric Dumazet 2010-09-21 21:17:32 +00:00 • committed by David S. Miller
parent b46ffb8545
commit 15cdeadaa5
1 changed files with 3 additions and 1 deletions
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4
net/netfilter/nf_conntrack_extend.c
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@ -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; unsigned int off, len;
struct nf_ct_ext_type *t; struct nf_ct_ext_type *t;
size_t alloc_size;
rcu_read_lock(); rcu_read_lock();
t = rcu_dereference(nf_ct_ext_types[id]); t = rcu_dereference(nf_ct_ext_types[id]);
BUG_ON(t == NULL); BUG_ON(t == NULL);
off = ALIGN(sizeof(struct nf_ct_ext), t->align); off = ALIGN(sizeof(struct nf_ct_ext), t->align);
len = off + t->len; len = off + t->len;
alloc_size = t->alloc_size;
rcu_read_unlock(); rcu_read_unlock();
*ext = kzalloc(t->alloc_size, gfp); *ext = kzalloc(alloc_size, gfp);
if (!*ext) if (!*ext)
return NULL; return NULL;