[PATCH 04/17] net: convert nf_bridge_info.use 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/linux/skbuff.h               | 6 +++---
 include/net/netfilter/br_netfilter.h | 2 +-
 net/bridge/br_netfilter_hooks.c      | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index a17e235..005793e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -252,7 +252,7 @@ struct nf_conntrack {
 
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 struct nf_bridge_info {
-       atomic_t                use;
+       refcount_t              use;
        enum {
                BRNF_PROTO_UNCHANGED,
                BRNF_PROTO_8021Q,
@@ -3589,13 +3589,13 @@ static inline void nf_conntrack_get(struct nf_conntrack 
*nfct)
 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
 static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
 {
-       if (nf_bridge && atomic_dec_and_test(&nf_bridge->use))
+       if (nf_bridge && refcount_dec_and_test(&nf_bridge->use))
                kfree(nf_bridge);
 }
 static inline void nf_bridge_get(struct nf_bridge_info *nf_bridge)
 {
        if (nf_bridge)
-               atomic_inc(&nf_bridge->use);
+               refcount_inc(&nf_bridge->use);
 }
 #endif /* CONFIG_BRIDGE_NETFILTER */
 static inline void nf_reset(struct sk_buff *skb)
diff --git a/include/net/netfilter/br_netfilter.h 
b/include/net/netfilter/br_netfilter.h
index 0b0c35c..925524e 100644
--- a/include/net/netfilter/br_netfilter.h
+++ b/include/net/netfilter/br_netfilter.h
@@ -8,7 +8,7 @@ static inline struct nf_bridge_info *nf_bridge_alloc(struct 
sk_buff *skb)
        skb->nf_bridge = kzalloc(sizeof(struct nf_bridge_info), GFP_ATOMIC);
 
        if (likely(skb->nf_bridge))
-               atomic_set(&(skb->nf_bridge->use), 1);
+               refcount_set(&(skb->nf_bridge->use), 1);
 
        return skb->nf_bridge;
 }
diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c
index 067cf03..2261e51 100644
--- a/net/bridge/br_netfilter_hooks.c
+++ b/net/bridge/br_netfilter_hooks.c
@@ -149,12 +149,12 @@ static inline struct nf_bridge_info 
*nf_bridge_unshare(struct sk_buff *skb)
 {
        struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 
-       if (atomic_read(&nf_bridge->use) > 1) {
+       if (refcount_read(&nf_bridge->use) > 1) {
                struct nf_bridge_info *tmp = nf_bridge_alloc(skb);
 
                if (tmp) {
                        memcpy(tmp, nf_bridge, sizeof(struct nf_bridge_info));
-                       atomic_set(&tmp->use, 1);
+                       refcount_set(&tmp->use, 1);
                }
                nf_bridge_put(nf_bridge);
                nf_bridge = tmp;
-- 
2.7.4