[PATCH 13/17] net: convert fib_rule.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/fib_rules.h | 7 ++++---
 net/core/fib_rules.c    | 4 ++--
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index 8dbfdf7..26ae0ad 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h
@@ -5,6 +5,7 @@
 #include <linux/slab.h>
 #include <linux/netdevice.h>
 #include <linux/fib_rules.h>
+#include <linux/refcount.h>
 #include <net/flow.h>
 #include <net/rtnetlink.h>
 
@@ -29,7 +30,7 @@ struct fib_rule {
        struct fib_rule __rcu   *ctarget;
        struct net              *fr_net;
 
-       atomic_t                refcnt;
+       refcount_t              refcnt;
        u32                     pref;
        int                     suppress_ifgroup;
        int                     suppress_prefixlen;
@@ -103,12 +104,12 @@ struct fib_rules_ops {
 
 static inline void fib_rule_get(struct fib_rule *rule)
 {
-       atomic_inc(&rule->refcnt);
+       refcount_inc(&rule->refcnt);
 }
 
 static inline void fib_rule_put(struct fib_rule *rule)
 {
-       if (atomic_dec_and_test(&rule->refcnt))
+       if (refcount_dec_and_test(&rule->refcnt))
                kfree_rcu(rule, rcu);
 }
 
diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index b6791d9..53d55d5 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -32,7 +32,7 @@ int fib_default_rule_add(struct fib_rules_ops *ops,
        if (r == NULL)
                return -ENOMEM;
 
-       atomic_set(&r->refcnt, 1);
+       refcount_set(&r->refcnt, 1);
        r->action = FR_ACT_TO_TBL;
        r->pref = pref;
        r->table = table;
@@ -269,7 +269,7 @@ int fib_rules_lookup(struct fib_rules_ops *ops, struct 
flowi *fl,
 
                if (err != -EAGAIN) {
                        if ((arg->flags & FIB_LOOKUP_NOREF) ||
-                           likely(atomic_inc_not_zero(&rule->refcnt))) {
+                           likely(refcount_inc_not_zero(&rule->refcnt))) {
                                arg->rule = rule;
                                goto out;
                        }
-- 
2.7.4