[PATCH 7/9] net, ipv6: convert ip6addrlbl_entry.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>
---
 net/ipv6/addrlabel.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/addrlabel.c b/net/ipv6/addrlabel.c
index 07cd7d2..7a428f6 100644
--- a/net/ipv6/addrlabel.c
+++ b/net/ipv6/addrlabel.c
@@ -18,6 +18,7 @@
 #include <linux/if_addrlabel.h>
 #include <linux/netlink.h>
 #include <linux/rtnetlink.h>
+#include <linux/refcount.h>
 
 #if 0
 #define ADDRLABEL(x...) printk(x)
@@ -36,7 +37,7 @@ struct ip6addrlbl_entry {
        int addrtype;
        u32 label;
        struct hlist_node list;
-       atomic_t refcnt;
+       refcount_t refcnt;
        struct rcu_head rcu;
 };
 
@@ -137,12 +138,12 @@ static void ip6addrlbl_free_rcu(struct rcu_head *h)
 
 static bool ip6addrlbl_hold(struct ip6addrlbl_entry *p)
 {
-       return atomic_inc_not_zero(&p->refcnt);
+       return refcount_inc_not_zero(&p->refcnt);
 }
 
 static inline void ip6addrlbl_put(struct ip6addrlbl_entry *p)
 {
-       if (atomic_dec_and_test(&p->refcnt))
+       if (refcount_dec_and_test(&p->refcnt))
                call_rcu(&p->rcu, ip6addrlbl_free_rcu);
 }
 
@@ -236,7 +237,7 @@ static struct ip6addrlbl_entry *ip6addrlbl_alloc(struct net 
*net,
        newp->label = label;
        INIT_HLIST_NODE(&newp->list);
        write_pnet(&newp->lbl_net, net);
-       atomic_set(&newp->refcnt, 1);
+       refcount_set(&newp->refcnt, 1);
        return newp;
 }
 
-- 
2.7.4