net: convert sk_buff.users from atomic_t to refcount_t

refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

6 files changed, 22 insertions, 22 deletions

diff --git a/net/core/datagram.c b/net/core/datagram.c
index e5311a7c70da..95d43543ac91 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -188,7 +188,7 @@ struct sk_buff *__skb_try_recv_from_queue(struct sock *sk,
 				}
 			}
 			*peeked = 1;
-			atomic_inc(&skb->users);
+			refcount_inc(&skb->users);
 		} else {
 			__skb_unlink(skb, queue);
 			if (destructor)
@@ -358,7 +358,7 @@ int __sk_queue_drop_skb(struct sock *sk, struct sk_buff_head *sk_queue,
 		spin_lock_bh(&sk_queue->lock);
 		if (skb == skb_peek(sk_queue)) {
 			__skb_unlink(skb, sk_queue);
-			atomic_dec(&skb->users);
+			refcount_dec(&skb->users);
 			if (destructor)
 				destructor(sk, skb);
 			err = 0;
diff --git a/net/core/dev.c b/net/core/dev.c
index 88927f1a3e4f..b9994898d11b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1862,7 +1862,7 @@ static inline int deliver_skb(struct sk_buff *skb,
 {
 	if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC)))
 		return -ENOMEM;
-	atomic_inc(&skb->users);
+	refcount_inc(&skb->users);
 	return pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
 }
 
@@ -2484,10 +2484,10 @@ void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
 	if (unlikely(!skb))
 		return;
 
-	if (likely(atomic_read(&skb->users) == 1)) {
+	if (likely(refcount_read(&skb->users) == 1)) {
 		smp_rmb();
-		atomic_set(&skb->users, 0);
-	} else if (likely(!atomic_dec_and_test(&skb->users))) {
+		refcount_set(&skb->users, 0);
+	} else if (likely(!refcount_dec_and_test(&skb->users))) {
 		return;
 	}
 	get_kfree_skb_cb(skb)->reason = reason;
@@ -3955,7 +3955,7 @@ static __latent_entropy void net_tx_action(struct softirq_action *h)
 
 			clist = clist->next;
 
-			WARN_ON(atomic_read(&skb->users));
+			WARN_ON(refcount_read(&skb->users));
 			if (likely(get_kfree_skb_cb(skb)->reason == SKB_REASON_CONSUMED))
 				trace_consume_skb(skb);
 			else
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 37c1e34ddd85..a835155c85f9 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -277,7 +277,7 @@ static void zap_completion_queue(void)
 			struct sk_buff *skb = clist;
 			clist = clist->next;
 			if (!skb_irq_freeable(skb)) {
-				atomic_inc(&skb->users);
+				refcount_inc(&skb->users);
 				dev_kfree_skb_any(skb); /* put this one back */
 			} else {
 				__kfree_skb(skb);
@@ -309,7 +309,7 @@ repeat:
 		return NULL;
 	}
 
-	atomic_set(&skb->users, 1);
+	refcount_set(&skb->users, 1);
 	skb_reserve(skb, reserve);
 	return skb;
 }
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index 2dd42c5b0366..6e1e10ff433a 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -3363,7 +3363,7 @@ static void pktgen_wait_for_skb(struct pktgen_dev *pkt_dev)
 {
 	ktime_t idle_start = ktime_get();
 
-	while (atomic_read(&(pkt_dev->skb->users)) != 1) {
+	while (refcount_read(&(pkt_dev->skb->users)) != 1) {
 		if (signal_pending(current))
 			break;
 
@@ -3420,7 +3420,7 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 	if (pkt_dev->xmit_mode == M_NETIF_RECEIVE) {
 		skb = pkt_dev->skb;
 		skb->protocol = eth_type_trans(skb, skb->dev);
-		atomic_add(burst, &skb->users);
+		refcount_add(burst, &skb->users);
 		local_bh_disable();
 		do {
 			ret = netif_receive_skb(skb);
@@ -3428,11 +3428,11 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 				pkt_dev->errors++;
 			pkt_dev->sofar++;
 			pkt_dev->seq_num++;
-			if (atomic_read(&skb->users) != burst) {
+			if (refcount_read(&skb->users) != burst) {
 				/* skb was queued by rps/rfs or taps,
 				 * so cannot reuse this skb
 				 */
-				atomic_sub(burst - 1, &skb->users);
+				WARN_ON(refcount_sub_and_test(burst - 1, &skb->users));
 				/* get out of the loop and wait
 				 * until skb is consumed
 				 */
@@ -3446,7 +3446,7 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 		goto out; /* Skips xmit_mode M_START_XMIT */
 	} else if (pkt_dev->xmit_mode == M_QUEUE_XMIT) {
 		local_bh_disable();
-		atomic_inc(&pkt_dev->skb->users);
+		refcount_inc(&pkt_dev->skb->users);
 
 		ret = dev_queue_xmit(pkt_dev->skb);
 		switch (ret) {
@@ -3487,7 +3487,7 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
 		pkt_dev->last_ok = 0;
 		goto unlock;
 	}
-	atomic_add(burst, &pkt_dev->skb->users);
+	refcount_add(burst, &pkt_dev->skb->users);
 
 xmit_more:
 	ret = netdev_start_xmit(pkt_dev->skb, odev, txq, --burst > 0);
@@ -3513,11 +3513,11 @@ xmit_more:
 		/* fallthru */
 	case NETDEV_TX_BUSY:
 		/* Retry it next time */
-		atomic_dec(&(pkt_dev->skb->users));
+		refcount_dec(&(pkt_dev->skb->users));
 		pkt_dev->last_ok = 0;
 	}
 	if (unlikely(burst))
-		atomic_sub(burst, &pkt_dev->skb->users);
+		WARN_ON(refcount_sub_and_test(burst, &pkt_dev->skb->users));
 unlock:
 	HARD_TX_UNLOCK(odev, txq);
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index ed51de525a88..d1ba90980be1 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -649,7 +649,7 @@ int rtnetlink_send(struct sk_buff *skb, struct net *net, u32 pid, unsigned int g
 
 	NETLINK_CB(skb).dst_group = group;
 	if (echo)
-		atomic_inc(&skb->users);
+		refcount_inc(&skb->users);
 	netlink_broadcast(rtnl, skb, pid, group, GFP_KERNEL);
 	if (echo)
 		err = netlink_unicast(rtnl, skb, pid, MSG_DONTWAIT);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f75897a33fa4..45dc6620dd74 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -176,7 +176,7 @@ struct sk_buff *__alloc_skb_head(gfp_t gfp_mask, int node)
 	memset(skb, 0, offsetof(struct sk_buff, tail));
 	skb->head = NULL;
 	skb->truesize = sizeof(struct sk_buff);
-	atomic_set(&skb->users, 1);
+	refcount_set(&skb->users, 1);
 
 	skb->mac_header = (typeof(skb->mac_header))~0U;
 out:
@@ -247,7 +247,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
 	/* Account for allocated memory : skb + skb->head */
 	skb->truesize = SKB_TRUESIZE(size);
 	skb->pfmemalloc = pfmemalloc;
-	atomic_set(&skb->users, 1);
+	refcount_set(&skb->users, 1);
 	skb->head = data;
 	skb->data = data;
 	skb_reset_tail_pointer(skb);
@@ -314,7 +314,7 @@ struct sk_buff *__build_skb(void *data, unsigned int frag_size)
 
 	memset(skb, 0, offsetof(struct sk_buff, tail));
 	skb->truesize = SKB_TRUESIZE(size);
-	atomic_set(&skb->users, 1);
+	refcount_set(&skb->users, 1);
 	skb->head = data;
 	skb->data = data;
 	skb_reset_tail_pointer(skb);
@@ -915,7 +915,7 @@ static struct sk_buff *__skb_clone(struct sk_buff *n, struct sk_buff *skb)
 	C(head_frag);
 	C(data);
 	C(truesize);
-	atomic_set(&n->users, 1);
+	refcount_set(&n->users, 1);
 
 	atomic_inc(&(skb_shinfo(skb)->dataref));
 	skb->cloned = 1;