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kernel: convert cgroup_namespace.count from atomic_t to refcount_t

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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>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Elena Reshetova 2017-02-20 12:19:00 +02:00 committed by Tejun Heo
parent c1ae3cfa0e
commit 387ad9674b
3 changed files with 6 additions and 5 deletions
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7
include/linux/cgroup.h
View File

@ -22,6 +22,7 @@
#include <linux/ns_common.h>
#include <linux/nsproxy.h>
#include <linux/user_namespace.h>
#include <linux/refcount.h>
#include <linux/cgroup-defs.h>
@ -640,7 +641,7 @@ static inline void cgroup_sk_free(struct sock_cgroup_data *skcd) {}
#endif /* CONFIG_CGROUP_DATA */
struct cgroup_namespace {
atomic_t count;
refcount_t count;
struct ns_common ns;
struct user_namespace *user_ns;
struct ucounts *ucounts;
@ -675,12 +676,12 @@ copy_cgroup_ns(unsigned long flags, struct user_namespace *user_ns,
static inline void get_cgroup_ns(struct cgroup_namespace *ns)
{
if (ns)
atomic_inc(&ns->count);
refcount_inc(&ns->count);
}
static inline void put_cgroup_ns(struct cgroup_namespace *ns)
{
if (ns && atomic_dec_and_test(&ns->count))
if (ns && refcount_dec_and_test(&ns->count))
free_cgroup_ns(ns);
}

2
kernel/cgroup/cgroup.c
View File

@ -189,7 +189,7 @@ static u16 have_canfork_callback __read_mostly;
/* cgroup namespace for init task */
struct cgroup_namespace init_cgroup_ns = {
.count = { .counter = 2, },
.count = REFCOUNT_INIT(2),
.user_ns = &init_user_ns,
.ns.ops = &cgroupns_operations,
.ns.inum = PROC_CGROUP_INIT_INO,

2
kernel/cgroup/namespace.c
View File

@ -31,7 +31,7 @@ static struct cgroup_namespace *alloc_cgroup_ns(void)
kfree(new_ns);
return ERR_PTR(ret);
}
atomic_set(&new_ns->count, 1);
refcount_set(&new_ns->count, 1);
new_ns->ns.ops = &cgroupns_operations;
return new_ns;
}