[PATCH 12/19] kernel: convert css_set.refcount from atomic_t to refcount_t
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(a)intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel(a)gmail.com>
Signed-off-by: Kees Cook <keescook(a)chromium.org>
Signed-off-by: David Windsor <dwindsor(a)gmail.com>
---
include/linux/cgroup-defs.h | 3 ++-
kernel/cgroup/cgroup-internal.h | 10 +++++++---
kernel/cgroup/cgroup-v1.c | 4 ++--
kernel/cgroup/cgroup.c | 8 ++++----
4 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 3c02404..e2f4b31 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -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;
diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 9203bfb..22d87ca 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -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
@@ -134,10 +135,13 @@ 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))
+ spin_lock_irqsave(&css_set_lock, flags);
+ if (refcount_read(&cset->refcount) != 1) {
+ WARN_ON(refcount_dec_and_test(&cset->refcount));
+ spin_unlock_irqrestore(&css_set_lock, flags);
return;
+ }
- spin_lock_irqsave(&css_set_lock, flags);
put_css_set_locked(cset);
spin_unlock_irqrestore(&css_set_lock, flags);
}
@@ -147,7 +151,7 @@ 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);
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index fc34bcf..9269179 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -343,7 +343,7 @@ 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;
}
@@ -1283,7 +1283,7 @@ 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;
}
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 5b94c79..59aba84 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -553,7 +553,7 @@ 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),
@@ -723,7 +723,7 @@ 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 */
@@ -976,7 +976,7 @@ 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);
@@ -5064,4 +5064,4 @@ int cgroup_bpf_update(struct cgroup *cgrp, struct bpf_prog *prog,
mutex_unlock(&cgroup_mutex);
return ret;
}
-#endif /* CONFIG_CGROUP_BPF */
+#endif /* CONFIG_CGROUP_BPF */
\ No newline at end of file
--
2.7.4