[PATCH 7/9] net, ipv6: convert ip6addrlbl_entry.refcnt from atomic_t to refcount_t

From: Elena Reshetova
Date: Thu Mar 16 2017 - 14:24:18 EST


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@xxxxxxxxx>
Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>
---
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 a8f6986..9340804 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