net: convert in_device.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.

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>
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index a7dd088..38d9af9 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -252,7 +252,7 @@
 	/* Reference in_dev->dev */
 	dev_hold(dev);
 	/* Account for reference dev->ip_ptr (below) */
-	in_dev_hold(in_dev);
+	refcount_set(&in_dev->refcnt, 1);
 
 	err = devinet_sysctl_register(in_dev);
 	if (err) {