[PATCH 1/9] net, ipv6: convert ipv6_txoptions.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/ipv6.h       | 7 ++++---
 net/ipv6/exthdrs.c       | 4 ++--
 net/ipv6/ipv6_sockglue.c | 2 +-
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 3e505bb..6eac5cf 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -16,6 +16,7 @@
 #include <linux/ipv6.h>
 #include <linux/hardirq.h>
 #include <linux/jhash.h>
+#include <linux/refcount.h>
 #include <net/if_inet6.h>
 #include <net/ndisc.h>
 #include <net/flow.h>
@@ -203,7 +204,7 @@ extern rwlock_t ip6_ra_lock;
  */
 
 struct ipv6_txoptions {
-       atomic_t                refcnt;
+       refcount_t              refcnt;
        /* Length of this structure */
        int                     tot_len;
 
@@ -265,7 +266,7 @@ static inline struct ipv6_txoptions *txopt_get(const struct 
ipv6_pinfo *np)
        rcu_read_lock();
        opt = rcu_dereference(np->opt);
        if (opt) {
-               if (!atomic_inc_not_zero(&opt->refcnt))
+               if (!refcount_inc_not_zero(&opt->refcnt))
                        opt = NULL;
                else
                        opt = rcu_pointer_handoff(opt);
@@ -276,7 +277,7 @@ static inline struct ipv6_txoptions *txopt_get(const struct 
ipv6_pinfo *np)
 
 static inline void txopt_put(struct ipv6_txoptions *opt)
 {
-       if (opt && atomic_dec_and_test(&opt->refcnt))
+       if (opt && refcount_dec_and_test(&opt->refcnt))
                kfree_rcu(opt, rcu);
 }
 
diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 0460af22..4996d73 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -971,7 +971,7 @@ ipv6_dup_options(struct sock *sk, struct ipv6_txoptions 
*opt)
                        *((char **)&opt2->dst1opt) += dif;
                if (opt2->srcrt)
                        *((char **)&opt2->srcrt) += dif;
-               atomic_set(&opt2->refcnt, 1);
+               refcount_set(&opt2->refcnt, 1);
        }
        return opt2;
 }
@@ -1056,7 +1056,7 @@ ipv6_renew_options(struct sock *sk, struct ipv6_txoptions 
*opt,
                return ERR_PTR(-ENOBUFS);
 
        memset(opt2, 0, tot_len);
-       atomic_set(&opt2->refcnt, 1);
+       refcount_set(&opt2->refcnt, 1);
        opt2->tot_len = tot_len;
        p = (char *)(opt2 + 1);
 
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index a531ba0..85404e7 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -505,7 +505,7 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, 
int optname,
                        break;
 
                memset(opt, 0, sizeof(*opt));
-               atomic_set(&opt->refcnt, 1);
+               refcount_set(&opt->refcnt, 1);
                opt->tot_len = sizeof(*opt) + optlen;
                retv = -EFAULT;
                if (copy_from_user(opt+1, optval, optlen))
-- 
2.7.4