[PATCH 12/17] net: convert unix_address.refcnt from atomic_t to refcount_t

[Elena Reshetova]

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.reshet...@intel.com>
Signed-off-by: Hans Liljestrand <ishkam...@gmail.com>
Signed-off-by: Kees Cook <keesc...@chromium.org>
Signed-off-by: David Windsor <dwind...@gmail.com>
---
 include/net/af_unix.h | 3 ++-
 net/unix/af_unix.c    | 8 ++++----
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index fd60ecc..3a385e4 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -4,6 +4,7 @@
 #include <linux/socket.h>
 #include <linux/un.h>
 #include <linux/mutex.h>
+#include <linux/refcount.h>
 #include <net/sock.h>
 
 void unix_inflight(struct user_struct *user, struct file *fp);
@@ -21,7 +22,7 @@ extern spinlock_t unix_table_lock;
 extern struct hlist_head unix_socket_table[2 * UNIX_HASH_SIZE];
 
 struct unix_address {
-       atomic_t        refcnt;
+       refcount_t      refcnt;
        int             len;
        unsigned int    hash;
        struct sockaddr_un name[0];
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index e9f8102..5e2a402 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -212,7 +212,7 @@ EXPORT_SYMBOL_GPL(unix_peer_get);
 
 static inline void unix_release_addr(struct unix_address *addr)
 {
-       if (atomic_dec_and_test(&addr->refcnt))
+       if (refcount_dec_and_test(&addr->refcnt))
                kfree(addr);
 }
 
@@ -861,7 +861,7 @@ static int unix_autobind(struct socket *sock)
                goto out;
 
        addr->name->sun_family = AF_UNIX;
-       atomic_set(&addr->refcnt, 1);
+       refcount_set(&addr->refcnt, 1);
 
 retry:
        addr->len = sprintf(addr->name->sun_path+1, "%05x", ordernum) + 1 + 
sizeof(short);
@@ -1036,7 +1036,7 @@ static int unix_bind(struct socket *sock, struct sockaddr 
*uaddr, int addr_len)
        memcpy(addr->name, sunaddr, addr_len);
        addr->len = addr_len;
        addr->hash = hash ^ sk->sk_type;
-       atomic_set(&addr->refcnt, 1);
+       refcount_set(&addr->refcnt, 1);
 
        if (sun_path[0]) {
                addr->hash = UNIX_HASH_SIZE;
@@ -1327,7 +1327,7 @@ static int unix_stream_connect(struct socket *sock, 
struct sockaddr *uaddr,
 
        /* copy address information from listening to new sock*/
        if (otheru->addr) {
-               atomic_inc(&otheru->addr->refcnt);
+               refcount_inc(&otheru->addr->refcnt);
                newu->addr = otheru->addr;
        }
        if (otheru->path.dentry) {
-- 
2.7.4