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>

5 files changed, 21 insertions, 18 deletions

diff --git a/include/linux/atmdev.h b/include/linux/atmdev.h
index c1da539f5e28..4d97a89da066 100644
--- a/include/linux/atmdev.h
+++ b/include/linux/atmdev.h
@@ -254,7 +254,7 @@ static inline void atm_return(struct atm_vcc *vcc,int truesize)
 
 static inline int atm_may_send(struct atm_vcc *vcc,unsigned int size)
 {
-	return (size + atomic_read(&sk_atm(vcc)->sk_wmem_alloc)) <
+	return (size + refcount_read(&sk_atm(vcc)->sk_wmem_alloc)) <
 	       sk_atm(vcc)->sk_sndbuf;
 }
 
diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index 12f6fba6d21a..97caf1821de8 100644
--- a/include/linux/igmp.h
+++ b/include/linux/igmp.h
@@ -18,6 +18,7 @@
 #include <linux/skbuff.h>
 #include <linux/timer.h>
 #include <linux/in.h>
+#include <linux/refcount.h>
 #include <uapi/linux/igmp.h>
 
 static inline struct igmphdr *igmp_hdr(const struct sk_buff *skb)
@@ -84,7 +85,7 @@ struct ip_mc_list {
 	struct ip_mc_list __rcu *next_hash;
 	struct timer_list	timer;
 	int			users;
-	atomic_t		refcnt;
+	refcount_t		refcnt;
 	spinlock_t		lock;
 	char			tm_running;
 	char			reporter;
diff --git a/include/linux/inetdevice.h b/include/linux/inetdevice.h
index e7c04c4e4bcd..fb3f809e34e4 100644
--- a/include/linux/inetdevice.h
+++ b/include/linux/inetdevice.h
@@ -11,6 +11,7 @@
 #include <linux/timer.h>
 #include <linux/sysctl.h>
 #include <linux/rtnetlink.h>
+#include <linux/refcount.h>
 
 struct ipv4_devconf {
 	void	*sysctl;
@@ -22,7 +23,7 @@ struct ipv4_devconf {
 
 struct in_device {
 	struct net_device	*dev;
-	atomic_t		refcnt;
+	refcount_t		refcnt;
 	int			dead;
 	struct in_ifaddr	*ifa_list;	/* IP ifaddr chain		*/
 
@@ -219,7 +220,7 @@ static inline struct in_device *in_dev_get(const struct net_device *dev)
 	rcu_read_lock();
 	in_dev = __in_dev_get_rcu(dev);
 	if (in_dev)
-		atomic_inc(&in_dev->refcnt);
+		refcount_inc(&in_dev->refcnt);
 	rcu_read_unlock();
 	return in_dev;
 }
@@ -240,12 +241,12 @@ void in_dev_finish_destroy(struct in_device *idev);
 
 static inline void in_dev_put(struct in_device *idev)
 {
-	if (atomic_dec_and_test(&idev->refcnt))
+	if (refcount_dec_and_test(&idev->refcnt))
 		in_dev_finish_destroy(idev);
 }
 
-#define __in_dev_put(idev)  atomic_dec(&(idev)->refcnt)
-#define in_dev_hold(idev)   atomic_inc(&(idev)->refcnt)
+#define __in_dev_put(idev)  refcount_dec(&(idev)->refcnt)
+#define in_dev_hold(idev)   refcount_inc(&(idev)->refcnt)
 
 #endif /* __KERNEL__ */
 
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 1828900c9411..27c0aaa22cb0 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -11,6 +11,7 @@
 #include <linux/interrupt.h>
 #include <linux/rcupdate.h>
 #include <linux/list.h>
+#include <linux/refcount.h>
 
 union inet_addr {
 	__u32		all[4];
@@ -34,7 +35,7 @@ struct netpoll {
 };
 
 struct netpoll_info {
-	atomic_t refcnt;
+	refcount_t refcnt;
 
 	struct semaphore dev_lock;
 
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a17e235639ae..d0b9f3846eab 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -252,7 +252,7 @@ struct nf_conntrack {
 
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 struct nf_bridge_info {
-	atomic_t		use;
+	refcount_t		use;
 	enum {
 		BRNF_PROTO_UNCHANGED,
 		BRNF_PROTO_8021Q,
@@ -761,7 +761,7 @@ struct sk_buff {
 	unsigned char		*head,
 				*data;
 	unsigned int		truesize;
-	atomic_t		users;
+	refcount_t		users;
 };
 
 #ifdef __KERNEL__
@@ -872,9 +872,9 @@ static inline bool skb_unref(struct sk_buff *skb)
 {
 	if (unlikely(!skb))
 		return false;
-	if (likely(atomic_read(&skb->users) == 1))
+	if (likely(refcount_read(&skb->users) == 1))
 		smp_rmb();
-	else if (likely(!atomic_dec_and_test(&skb->users)))
+	else if (likely(!refcount_dec_and_test(&skb->users)))
 		return false;
 
 	return true;
@@ -915,7 +915,7 @@ struct sk_buff_fclones {
 
 	struct sk_buff	skb2;
 
-	atomic_t	fclone_ref;
+	refcount_t	fclone_ref;
 };
 
 /**
@@ -935,7 +935,7 @@ static inline bool skb_fclone_busy(const struct sock *sk,
 	fclones = container_of(skb, struct sk_buff_fclones, skb1);
 
 	return skb->fclone == SKB_FCLONE_ORIG &&
-	       atomic_read(&fclones->fclone_ref) > 1 &&
+	       refcount_read(&fclones->fclone_ref) > 1 &&
 	       fclones->skb2.sk == sk;
 }
 
@@ -1283,7 +1283,7 @@ static inline struct sk_buff *skb_queue_prev(const struct sk_buff_head *list,
  */
 static inline struct sk_buff *skb_get(struct sk_buff *skb)
 {
-	atomic_inc(&skb->users);
+	refcount_inc(&skb->users);
 	return skb;
 }
 
@@ -1384,7 +1384,7 @@ static inline void __skb_header_release(struct sk_buff *skb)
  */
 static inline int skb_shared(const struct sk_buff *skb)
 {
-	return atomic_read(&skb->users) != 1;
+	return refcount_read(&skb->users) != 1;
 }
 
 /**
@@ -3589,13 +3589,13 @@ static inline void nf_conntrack_get(struct nf_conntrack *nfct)
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
 {
-	if (nf_bridge && atomic_dec_and_test(&nf_bridge->use))
+	if (nf_bridge && refcount_dec_and_test(&nf_bridge->use))
 		kfree(nf_bridge);
 }
 static inline void nf_bridge_get(struct nf_bridge_info *nf_bridge)
 {
 	if (nf_bridge)
-		atomic_inc(&nf_bridge->use);
+		refcount_inc(&nf_bridge->use);
 }
 #endif /* CONFIG_BRIDGE_NETFILTER */
 static inline void nf_reset(struct sk_buff *skb)