Commit 9ac25fc0 authored Mar 03, 2017 by Eric Dumazet Committed by David S. Miller Mar 07, 2017

net: fix socket refcounting in skb_complete_tx_timestamp()



TX skbs do not necessarily hold a reference on skb->sk->sk_refcnt
By the time TX completion happens, sk_refcnt might be already 0.

sock_hold()/sock_put() would then corrupt critical state, like
sk_wmem_alloc and lead to leaks or use after free.

Fixes: 62bccb8c ("net-timestamp: Make the clone operation stand-alone from phy timestamping")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent dd4f1072

net/core/skbuff.c

+8 −7

Original line number	Diff line number	Diff line
		@@ -3828,14 +3828,15 @@ void skb_complete_tx_timestamp(struct sk_buff *skb,
		if (!skb_may_tx_timestamp(sk, false))
		return;

		/* take a reference to prevent skb_orphan() from freeing the socket */
		sock_hold(sk);

		/* Take a reference to prevent skb_orphan() from freeing the socket,
		* but only if the socket refcount is not zero.
		*/
		if (likely(atomic_inc_not_zero(&sk->sk_refcnt))) {
		skb_hwtstamps(skb) = hwtstamps;
		__skb_complete_tx_timestamp(skb, sk, SCM_TSTAMP_SND);

		sock_put(sk);
		}
		}
		EXPORT_SYMBOL_GPL(skb_complete_tx_timestamp);

		void __skb_tstamp_tx(struct sk_buff *orig_skb,

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