[PATCH 04/17] net: convert nf_bridge_info.use from atomic_t to refcount_t

From: Elena Reshetova
Date: Fri Jun 30 2017 - 06:14:27 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>
---
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