net: convert sock.sk_refcnt 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.

This patch uses refcount_inc_not_zero() instead of
atomic_inc_not_zero_hint() due to absense of a _hint()
version of refcount API. If the hint() version must
be used, we might need to revisit API.

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>

3 files changed, 16 insertions, 14 deletions

diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
index 1178931288cb..b9e6e0e1f55c 100644
--- a/include/net/inet_hashtables.h
+++ b/include/net/inet_hashtables.h
@@ -32,7 +32,7 @@
 #include <net/tcp_states.h>
 #include <net/netns/hash.h>
 
-#include <linux/atomic.h>
+#include <linux/refcount.h>
 #include <asm/byteorder.h>
 
 /* This is for all connections with a full identity, no wildcards.
@@ -334,7 +334,7 @@ static inline struct sock *inet_lookup(struct net *net,
 	sk = __inet_lookup(net, hashinfo, skb, doff, saddr, sport, daddr,
 			   dport, dif, &refcounted);
 
-	if (sk && !refcounted && !atomic_inc_not_zero(&sk->sk_refcnt))
+	if (sk && !refcounted && !refcount_inc_not_zero(&sk->sk_refcnt))
 		sk = NULL;
 	return sk;
 }
diff --git a/include/net/request_sock.h b/include/net/request_sock.h
index 53ced67c4ae9..23e22054aa60 100644
--- a/include/net/request_sock.h
+++ b/include/net/request_sock.h
@@ -19,6 +19,7 @@
 #include <linux/spinlock.h>
 #include <linux/types.h>
 #include <linux/bug.h>
+#include <linux/refcount.h>
 
 #include <net/sock.h>
 
@@ -89,7 +90,7 @@ reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
 		return NULL;
 	req->rsk_listener = NULL;
 	if (attach_listener) {
-		if (unlikely(!atomic_inc_not_zero(&sk_listener->sk_refcnt))) {
+		if (unlikely(!refcount_inc_not_zero(&sk_listener->sk_refcnt))) {
 			kmem_cache_free(ops->slab, req);
 			return NULL;
 		}
@@ -100,7 +101,7 @@ reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
 	sk_node_init(&req_to_sk(req)->sk_node);
 	sk_tx_queue_clear(req_to_sk(req));
 	req->saved_syn = NULL;
-	atomic_set(&req->rsk_refcnt, 0);
+	refcount_set(&req->rsk_refcnt, 0);
 
 	return req;
 }
@@ -108,7 +109,7 @@ reqsk_alloc(const struct request_sock_ops *ops, struct sock *sk_listener,
 static inline void reqsk_free(struct request_sock *req)
 {
 	/* temporary debugging */
-	WARN_ON_ONCE(atomic_read(&req->rsk_refcnt) != 0);
+	WARN_ON_ONCE(refcount_read(&req->rsk_refcnt) != 0);
 
 	req->rsk_ops->destructor(req);
 	if (req->rsk_listener)
@@ -119,7 +120,7 @@ static inline void reqsk_free(struct request_sock *req)
 
 static inline void reqsk_put(struct request_sock *req)
 {
-	if (atomic_dec_and_test(&req->rsk_refcnt))
+	if (refcount_dec_and_test(&req->rsk_refcnt))
 		reqsk_free(req);
 }
 
diff --git a/include/net/sock.h b/include/net/sock.h
index 5284e50fc81a..60200f4f4028 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -66,6 +66,7 @@
 #include <linux/poll.h>
 
 #include <linux/atomic.h>
+#include <linux/refcount.h>
 #include <net/dst.h>
 #include <net/checksum.h>
 #include <net/tcp_states.h>
@@ -219,7 +220,7 @@ struct sock_common {
 		u32		skc_tw_rcv_nxt; /* struct tcp_timewait_sock  */
 	};
 
-	atomic_t		skc_refcnt;
+	refcount_t		skc_refcnt;
 	/* private: */
 	int                     skc_dontcopy_end[0];
 	union {
@@ -611,7 +612,7 @@ static inline bool __sk_del_node_init(struct sock *sk)
 
 static __always_inline void sock_hold(struct sock *sk)
 {
-	atomic_inc(&sk->sk_refcnt);
+	refcount_inc(&sk->sk_refcnt);
 }
 
 /* Ungrab socket in the context, which assumes that socket refcnt
@@ -619,7 +620,7 @@ static __always_inline void sock_hold(struct sock *sk)
  */
 static __always_inline void __sock_put(struct sock *sk)
 {
-	atomic_dec(&sk->sk_refcnt);
+	refcount_dec(&sk->sk_refcnt);
 }
 
 static inline bool sk_del_node_init(struct sock *sk)
@@ -628,7 +629,7 @@ static inline bool sk_del_node_init(struct sock *sk)
 
 	if (rc) {
 		/* paranoid for a while -acme */
-		WARN_ON(atomic_read(&sk->sk_refcnt) == 1);
+		WARN_ON(refcount_read(&sk->sk_refcnt) == 1);
 		__sock_put(sk);
 	}
 	return rc;
@@ -650,7 +651,7 @@ static inline bool sk_nulls_del_node_init_rcu(struct sock *sk)
 
 	if (rc) {
 		/* paranoid for a while -acme */
-		WARN_ON(atomic_read(&sk->sk_refcnt) == 1);
+		WARN_ON(refcount_read(&sk->sk_refcnt) == 1);
 		__sock_put(sk);
 	}
 	return rc;
@@ -1144,9 +1145,9 @@ static inline void sk_refcnt_debug_dec(struct sock *sk)
 
 static inline void sk_refcnt_debug_release(const struct sock *sk)
 {
-	if (atomic_read(&sk->sk_refcnt) != 1)
+	if (refcount_read(&sk->sk_refcnt) != 1)
 		printk(KERN_DEBUG "Destruction of the %s socket %p delayed, refcnt=%d\n",
-		       sk->sk_prot->name, sk, atomic_read(&sk->sk_refcnt));
+		       sk->sk_prot->name, sk, refcount_read(&sk->sk_refcnt));
 }
 #else /* SOCK_REFCNT_DEBUG */
 #define sk_refcnt_debug_inc(sk) do { } while (0)
@@ -1636,7 +1637,7 @@ void sock_init_data(struct socket *sock, struct sock *sk);
 /* Ungrab socket and destroy it, if it was the last reference. */
 static inline void sock_put(struct sock *sk)
 {
-	if (atomic_dec_and_test(&sk->sk_refcnt))
+	if (refcount_dec_and_test(&sk->sk_refcnt))
 		sk_free(sk);
 }
 /* Generic version of sock_put(), dealing with all sockets