Merge branch 'net-refcount_t'

Elena Reshetova says:

====================
v3 net generic subsystem refcount conversions

Changes in v3:
Rebased on top of the net-next tree.

Changes in v2:
No changes in patches apart from rebases, but now by
default refcount_t = atomic_t (*) and uses all atomic standard operations
unless CONFIG_REFCOUNT_FULL is enabled. This is a compromise for the
systems that are critical on performance (such as net) and cannot accept even
slight delay on the refcounter operations.

This series, for core network subsystem components, replaces atomic_t reference
counters with the new refcount_t type and API (see include/linux/refcount.h).
By doing this we prevent intentional or accidental
underflows or overflows that can led to use-after-free vulnerabilities.
These patches contain only generic net pieces. Other changes will be sent separately.

The patches are fully independent and can be cherry-picked separately.
The big patches, such as conversions for sock structure, need a very detailed
look from maintainers: refcount managing is quite complex in them and while
it seems that they would benefit from the change, extra checking is needed.
The biggest corner issue is the fact that refcount_inc() does not increment
from zero.

If there are no objections to the patches, please merge them via respective trees.

* The respective change is currently merged into -next as
  "locking/refcount: Create unchecked atomic_t implementation".
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 12 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 00d09140e354..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 {
@@ -390,7 +391,7 @@ struct sock {
 
 	/* ===== cache line for TX ===== */
 	int			sk_wmem_queued;
-	atomic_t		sk_wmem_alloc;
+	refcount_t		sk_wmem_alloc;
 	unsigned long		sk_tsq_flags;
 	struct sk_buff		*sk_send_head;
 	struct sk_buff_head	sk_write_queue;
@@ -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
@@ -1911,7 +1912,7 @@ static inline int skb_copy_to_page_nocache(struct sock *sk, struct iov_iter *fro
  */
 static inline int sk_wmem_alloc_get(const struct sock *sk)
 {
-	return atomic_read(&sk->sk_wmem_alloc) - 1;
+	return refcount_read(&sk->sk_wmem_alloc) - 1;
 }
 
 /**
@@ -2055,7 +2056,7 @@ static inline unsigned long sock_wspace(struct sock *sk)
 	int amt = 0;
 
 	if (!(sk->sk_shutdown & SEND_SHUTDOWN)) {
-		amt = sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc);
+		amt = sk->sk_sndbuf - refcount_read(&sk->sk_wmem_alloc);
 		if (amt < 0)
 			amt = 0;
 	}
@@ -2136,7 +2137,7 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag);
  */
 static inline bool sock_writeable(const struct sock *sk)
 {
-	return atomic_read(&sk->sk_wmem_alloc) < (sk->sk_sndbuf >> 1);
+	return refcount_read(&sk->sk_wmem_alloc) < (sk->sk_sndbuf >> 1);
 }
 
 static inline gfp_t gfp_any(void)