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Commit 47e958ea authored by Pavel Emelyanov's avatar Pavel Emelyanov Committed by David S. Miller
Browse files

[NET]: Fix the race between sk_filter_(de|at)tach and sk_clone() 



The proposed fix is to delay the reference counter decrement
until the quiescent state pass. This will give sk_clone() a
chance to get the reference on the cloned filter.

Regular sk_filter_uncharge can happen from the sk_free() only
and there's no need in delaying the put - the socket is dead
anyway and is to be release itself.

Signed-off-by: default avatarPavel Emelyanov <xemul@openvz.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d3904b73

include/net/sock.h

+1 −11
Original line number Diff line number Diff line
@@ -904,16 +904,6 @@ static inline int sk_filter(struct sock *sk, struct sk_buff *skb) 
	return err;

}



/**

 * 	sk_filter_rcu_free: Free a socket filter

 *	@rcu: rcu_head that contains the sk_filter to free

 */

static inline void sk_filter_rcu_free(struct rcu_head *rcu)

{

	struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);

	kfree(fp);

}



/**

 *	sk_filter_release: Release a socket filter

 *	@sk: socket
@@ -925,7 +915,7 @@ static inline void sk_filter_rcu_free(struct rcu_head *rcu) 
static inline void sk_filter_release(struct sk_filter *fp)

{

	if (atomic_dec_and_test(&fp->refcnt))

		call_rcu_bh(&fp->rcu, sk_filter_rcu_free);

		kfree(fp);

}



static inline void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)

net/core/filter.c

+21 −2
Original line number Diff line number Diff line
@@ -386,6 +386,25 @@ int sk_chk_filter(struct sock_filter *filter, int flen) 
	return (BPF_CLASS(filter[flen - 1].code) == BPF_RET) ? 0 : -EINVAL;

}



/**

 * 	sk_filter_rcu_release: Release a socket filter by rcu_head

 *	@rcu: rcu_head that contains the sk_filter to free

 */

static void sk_filter_rcu_release(struct rcu_head *rcu)

{

	struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);



	sk_filter_release(fp);

}



static void sk_filter_delayed_uncharge(struct sock *sk, struct sk_filter *fp)

{

	unsigned int size = sk_filter_len(fp);



	atomic_sub(size, &sk->sk_omem_alloc);

	call_rcu_bh(&fp->rcu, sk_filter_rcu_release);

}



/**

 *	sk_attach_filter - attach a socket filter

 *	@fprog: the filter program
@@ -428,7 +447,7 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) 
	rcu_assign_pointer(sk->sk_filter, fp);

	rcu_read_unlock_bh();



	sk_filter_uncharge(sk, old_fp);

	sk_filter_delayed_uncharge(sk, old_fp);

	return 0;

}
@@ -441,7 +460,7 @@ int sk_detach_filter(struct sock *sk) 
	filter = rcu_dereference(sk->sk_filter);

	if (filter) {

		rcu_assign_pointer(sk->sk_filter, NULL);

		sk_filter_uncharge(sk, filter);

		sk_filter_delayed_uncharge(sk, filter);

		ret = 0;

	}

	rcu_read_unlock_bh();