drivers, connector: convert cn_callback_entry.refcnt from atomic_t to refcount_t
atomic_t variables are currently used to implement reference counters with the following properties: - counter is initialized to 1 using atomic_set() - a resource is freed upon counter reaching zero - once counter reaches zero, its further increments aren't allowed - counter schema uses basic atomic operations (set, inc, inc_not_zero, dec_and_test, etc.) Such atomic variables should be converted to a newly provided refcount_t type and API that prevents accidental counter overflows and underflows. This is important since overflows and underflows can lead to use-after-free situation and be exploitable. The variable cn_callback_entry.refcnt is used as pure reference counter. Convert it to refcount_t and fix up the operations. Suggested-by: Kees Cook <keescook@chromium.org> Reviewed-by: David Windsor <dwindsor@gmail.com> Reviewed-by: Hans Liljestrand <ishkamiel@gmail.com> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -45,7 +45,7 @@ cn_queue_alloc_callback_entry(struct cn_queue_dev *dev, const char *name,
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return NULL;
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}
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atomic_set(&cbq->refcnt, 1);
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refcount_set(&cbq->refcnt, 1);
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atomic_inc(&dev->refcnt);
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cbq->pdev = dev;
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@ -58,7 +58,7 @@ cn_queue_alloc_callback_entry(struct cn_queue_dev *dev, const char *name,
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void cn_queue_release_callback(struct cn_callback_entry *cbq)
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{
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if (!atomic_dec_and_test(&cbq->refcnt))
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if (!refcount_dec_and_test(&cbq->refcnt))
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return;
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atomic_dec(&cbq->pdev->refcnt);
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@ -157,7 +157,7 @@ static int cn_call_callback(struct sk_buff *skb)
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spin_lock_bh(&dev->cbdev->queue_lock);
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list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
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if (cn_cb_equal(&i->id.id, &msg->id)) {
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atomic_inc(&i->refcnt);
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refcount_inc(&i->refcnt);
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cbq = i;
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break;
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}
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@ -22,7 +22,7 @@
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#define __CONNECTOR_H
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#include <linux/atomic.h>
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#include <linux/refcount.h>
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#include <linux/list.h>
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#include <linux/workqueue.h>
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@ -49,7 +49,7 @@ struct cn_callback_id {
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struct cn_callback_entry {
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struct list_head callback_entry;
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atomic_t refcnt;
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refcount_t refcnt;
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struct cn_queue_dev *pdev;
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struct cn_callback_id id;
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