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kernel: convert css_set.refcount 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 2017-03-08 10:00:40 +02:00 committed by Tejun Heo
parent 387ad9674b
commit 4b9502e63b
4 changed files with 10 additions and 8 deletions
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3
include/linux/cgroup-defs.h
View File

@ -13,6 +13,7 @@
#include <linux/wait.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/refcount.h>
#include <linux/percpu-refcount.h>
#include <linux/percpu-rwsem.h>
#include <linux/workqueue.h>
@ -156,7 +157,7 @@ struct css_set {
struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
/* reference count */
atomic_t refcount;
refcount_t refcount;
/* the default cgroup associated with this css_set */
struct cgroup *dfl_cgrp;

5
kernel/cgroup/cgroup-internal.h
View File

@ -5,6 +5,7 @@
#include <linux/kernfs.h>
#include <linux/workqueue.h>
#include <linux/list.h>
#include <linux/refcount.h>
/*
* A cgroup can be associated with multiple css_sets as different tasks may
@ -134,7 +135,7 @@ static inline void put_css_set(struct css_set *cset)
* can see it. Similar to atomic_dec_and_lock(), but for an
* rwlock
*/
if (atomic_add_unless(&cset->refcount, -1, 1))
if (refcount_dec_not_one(&cset->refcount))
return;
spin_lock_irqsave(&css_set_lock, flags);
@ -147,7 +148,7 @@ static inline void put_css_set(struct css_set *cset)
*/
static inline void get_css_set(struct css_set *cset)
{
atomic_inc(&cset->refcount);
refcount_inc(&cset->refcount);
}
bool cgroup_ssid_enabled(int ssid);

4
kernel/cgroup/cgroup-v1.c
View File

@ -346,7 +346,7 @@ static int cgroup_task_count(const struct cgroup *cgrp)
spin_lock_irq(&css_set_lock);
list_for_each_entry(link, &cgrp->cset_links, cset_link)
count += atomic_read(&link->cset->refcount);
count += refcount_read(&link->cset->refcount);
spin_unlock_irq(&css_set_lock);
return count;
}
@ -1286,7 +1286,7 @@ static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
u64 count;
rcu_read_lock();
count = atomic_read(&task_css_set(current)->refcount);
count = refcount_read(&task_css_set(current)->refcount);
rcu_read_unlock();
return count;
}

6
kernel/cgroup/cgroup.c
View File

@ -554,7 +554,7 @@ EXPORT_SYMBOL_GPL(of_css);
* haven't been created.
*/
struct css_set init_css_set = {
.refcount = ATOMIC_INIT(1),
.refcount = REFCOUNT_INIT(1),
.tasks = LIST_HEAD_INIT(init_css_set.tasks),
.mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
.task_iters = LIST_HEAD_INIT(init_css_set.task_iters),
@ -724,7 +724,7 @@ void put_css_set_locked(struct css_set *cset)
lockdep_assert_held(&css_set_lock);
if (!atomic_dec_and_test(&cset->refcount))
if (!refcount_dec_and_test(&cset->refcount))
return;
/* This css_set is dead. unlink it and release cgroup and css refs */
@ -977,7 +977,7 @@ static struct css_set *find_css_set(struct css_set *old_cset,
return NULL;
}
atomic_set(&cset->refcount, 1);
refcount_set(&cset->refcount, 1);
INIT_LIST_HEAD(&cset->tasks);
INIT_LIST_HEAD(&cset->mg_tasks);
INIT_LIST_HEAD(&cset->task_iters);