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Commit 15cdeada authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Reviewed-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b46ffb85

net/netfilter/nf_conntrack_extend.c

+3 −1
Original line number Diff line number Diff line
@@ -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;