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From: Elena Reshetova <elena.reshetova@intel.com>
To: linux-kernel@vger.kernel.org
Cc: cgroups@vger.kernel.org, linux-audit@redhat.com,
	linux-fsdevel@vger.kernel.org, peterz@infradead.org,
	gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk,
	tj@kernel.org, mingo@redhat.com, hannes@cmpxchg.org,
	lizefan@huawei.com, acme@kernel.org,
	alexander.shishkin@linux.intel.com, paul@paul-moore.com,
	eparis@redhat.com, akpm@linux-foundation.org, arnd@arndb.de,
	luto@kernel.org, Elena Reshetova <elena.reshetova@intel.com>,
	Hans Liljestrand <ishkamiel@gmail.com>,
	Kees Cook <keescook@chromium.org>,
	David Windsor <dwindsor@gmail.com>
Subject: [PATCH 12/19] kernel: convert css_set.refcount from atomic_t to refcount_t
Date: Mon, 20 Feb 2017 12:19:01 +0200	[thread overview]
Message-ID: <1487585948-6401-13-git-send-email-elena.reshetova@intel.com> (raw)
In-Reply-To: <1487585948-6401-1-git-send-email-elena.reshetova@intel.com>

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/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

  parent reply	other threads:[~2017-02-20 10:25 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-20 10:18 [PATCH 00/19] Kernel subsystem refcounter conversions Elena Reshetova
2017-02-20 10:18 ` [PATCH 01/19] kernel: convert sighand_struct.count from atomic_t to refcount_t Elena Reshetova
2017-02-20 12:30   ` kbuild test robot
2017-02-20 12:42   ` kbuild test robot
2017-02-20 10:18 ` [PATCH 02/19] kernel: convert signal_struct.sigcnt " Elena Reshetova
2017-02-20 10:18 ` [PATCH 03/19] kernel: convert user_struct.__count " Elena Reshetova
2017-02-20 10:18 ` [PATCH 04/19] kernel: convert task_struct.usage " Elena Reshetova
2017-02-20 10:18 ` [PATCH 05/19] kernel: convert task_struct.stack_refcount " Elena Reshetova
2017-02-20 10:18 ` [PATCH 06/19] kernel: convert perf_event_context.refcount " Elena Reshetova
2017-02-20 10:28   ` Peter Zijlstra
2017-02-20 12:14     ` Reshetova, Elena
2017-02-20 10:18 ` [PATCH 07/19] kernel: convert ring_buffer.refcount " Elena Reshetova
2017-02-20 10:18 ` [PATCH 08/19] kernel: convert ring_buffer.aux_refcount " Elena Reshetova
2017-02-20 10:18 ` [PATCH 09/19] kernel: convert uprobe.ref " Elena Reshetova
2017-02-20 10:18 ` [PATCH 10/19] kernel: convert nsproxy.count " Elena Reshetova
2017-02-20 10:19 ` [PATCH 11/19] kernel: convert cgroup_namespace.count " Elena Reshetova
2017-03-06 19:55   ` Tejun Heo
2017-02-20 10:19 ` Elena Reshetova [this message]
2017-03-06 19:54   ` [PATCH 12/19] kernel: convert css_set.refcount " Tejun Heo
2017-03-07 19:12     ` Reshetova, Elena
2017-03-07 19:21       ` Tejun Heo
2017-02-20 10:19 ` [PATCH 13/19] kernel: convert group_info.usage " Elena Reshetova
2017-02-20 10:19 ` [PATCH 14/19] kernel: convert cred.usage " Elena Reshetova
2017-02-20 10:19 ` [PATCH 15/19] kernel: convert audit_tree.count " Elena Reshetova
2017-02-20 22:07   ` Paul Moore
2017-02-21  7:15     ` Reshetova, Elena
2017-02-28 22:11       ` Paul Moore
2017-03-01  0:16         ` Kees Cook
2017-03-01 19:35           ` Paul Moore
2017-03-01 23:04             ` Kees Cook
2017-04-11 19:01         ` Paul Moore
2017-04-18  6:33           ` Reshetova, Elena
2017-02-20 10:19 ` [PATCH 16/19] kernel: convert audit_watch.count " Elena Reshetova
2017-02-20 10:19 ` [PATCH 17/19] kernel: convert numa_group.refcount " Elena Reshetova
2017-02-20 10:19 ` [PATCH 18/19] kernel: convert futex_pi_state.refcount " Elena Reshetova
2017-02-20 10:19 ` [PATCH 19/19] kernel: convert kcov.refcount " Elena Reshetova

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