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Subject[PATCH 15/17] net: convert net.passive from atomic_t to refcount_t
Date
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@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
---
include/net/net_namespace.h | 3 ++-
net/core/net-sysfs.c | 2 +-
net/core/net_namespace.c | 4 ++--
3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index fe80bb4..bffe0a3 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -5,6 +5,7 @@
#define __NET_NET_NAMESPACE_H

#include <linux/atomic.h>
+#include <linux/refcount.h>
#include <linux/workqueue.h>
#include <linux/list.h>
#include <linux/sysctl.h>
@@ -46,7 +47,7 @@ struct netns_ipvs;
#define NETDEV_HASHENTRIES (1 << NETDEV_HASHBITS)

struct net {
- atomic_t passive; /* To decided when the network
+ refcount_t passive; /* To decided when the network
* namespace should be freed.
*/
atomic_t count; /* To decided when the network
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index fe7e145..b4f9922 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1448,7 +1448,7 @@ static void *net_grab_current_ns(void)
struct net *ns = current->nsproxy->net_ns;
#ifdef CONFIG_NET_NS
if (ns)
- atomic_inc(&ns->passive);
+ refcount_inc(&ns->passive);
#endif
return ns;
}
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 2178db8..57feb1e 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -284,7 +284,7 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
LIST_HEAD(net_exit_list);

atomic_set(&net->count, 1);
- atomic_set(&net->passive, 1);
+ refcount_set(&net->passive, 1);
net->dev_base_seq = 1;
net->user_ns = user_ns;
idr_init(&net->netns_ids);
@@ -380,7 +380,7 @@ static void net_free(struct net *net)
void net_drop_ns(void *p)
{
struct net *ns = p;
- if (ns && atomic_dec_and_test(&ns->passive))
+ if (ns && refcount_dec_and_test(&ns->passive))
net_free(ns);
}

--
2.7.4
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