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Subject[PATCH 1/3] ipc: convert ipc_namespace.count 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/linux/ipc_namespace.h | 5 +++--
ipc/msgutil.c | 2 +-
ipc/namespace.c | 4 ++--
3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index 65327ee..e81445c 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -7,6 +7,7 @@
#include <linux/notifier.h>
#include <linux/nsproxy.h>
#include <linux/ns_common.h>
+#include <linux/refcount.h>

struct user_namespace;

@@ -19,7 +20,7 @@ struct ipc_ids {
};

struct ipc_namespace {
- atomic_t count;
+ refcount_t count;
struct ipc_ids ids[3];

int sem_ctls[4];
@@ -118,7 +119,7 @@ extern struct ipc_namespace *copy_ipcs(unsigned long flags,
static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
{
if (ns)
- atomic_inc(&ns->count);
+ refcount_inc(&ns->count);
return ns;
}

diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index bf74eaa..8459802 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -29,7 +29,7 @@ DEFINE_SPINLOCK(mq_lock);
* and not CONFIG_IPC_NS.
*/
struct ipc_namespace init_ipc_ns = {
- .count = ATOMIC_INIT(1),
+ .count = REFCOUNT_INIT(1),
.user_ns = &init_user_ns,
.ns.inum = PROC_IPC_INIT_INO,
#ifdef CONFIG_IPC_NS
diff --git a/ipc/namespace.c b/ipc/namespace.c
index b4d80f9..7af6e6b 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -50,7 +50,7 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
goto fail_free;
ns->ns.ops = &ipcns_operations;

- atomic_set(&ns->count, 1);
+ refcount_set(&ns->count, 1);
ns->user_ns = get_user_ns(user_ns);
ns->ucounts = ucounts;

@@ -144,7 +144,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
*/
void put_ipc_ns(struct ipc_namespace *ns)
{
- if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
+ if (refcount_dec_and_lock(&ns->count, &mq_lock)) {
mq_clear_sbinfo(ns);
spin_unlock(&mq_lock);
mq_put_mnt(ns);
--
2.7.4
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