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Commit d780cd44 authored by Elena Reshetova's avatar Elena Reshetova Committed by David S. Miller
Browse files

drivers, net, ppp: convert ppp_file.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 ppp_file.refcnt is used as pure reference counter.
Convert it to refcount_t and fix up the operations.

Suggested-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarDavid Windsor <dwindsor@gmail.com>
Reviewed-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 313a9121

drivers/net/ppp/ppp_generic.c

+11 −10
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ 
#include <asm/unaligned.h>

#include <net/slhc_vj.h>

#include <linux/atomic.h>

#include <linux/refcount.h>



#include <linux/nsproxy.h>

#include <net/net_namespace.h>
@@ -84,7 +85,7 @@ struct ppp_file { 
	struct sk_buff_head xq;		/* pppd transmit queue */

	struct sk_buff_head rq;		/* receive queue for pppd */

	wait_queue_head_t rwait;	/* for poll on reading /dev/ppp */

	atomic_t	refcnt;		/* # refs (incl /dev/ppp attached) */

	refcount_t	refcnt;		/* # refs (incl /dev/ppp attached) */

	int		hdrlen;		/* space to leave for headers */

	int		index;		/* interface unit / channel number */

	int		dead;		/* unit/channel has been shut down */
@@ -408,7 +409,7 @@ static int ppp_release(struct inode *unused, struct file *file) 
				unregister_netdevice(ppp->dev);

			rtnl_unlock();

		}

		if (atomic_dec_and_test(&pf->refcnt)) {

		if (refcount_dec_and_test(&pf->refcnt)) {

			switch (pf->kind) {

			case INTERFACE:

				ppp_destroy_interface(PF_TO_PPP(pf));
@@ -881,7 +882,7 @@ static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf, 
		mutex_lock(&pn->all_ppp_mutex);

		ppp = ppp_find_unit(pn, unit);

		if (ppp) {

			atomic_inc(&ppp->file.refcnt);

			refcount_inc(&ppp->file.refcnt);

			file->private_data = &ppp->file;

			err = 0;

		}
@@ -896,7 +897,7 @@ static int ppp_unattached_ioctl(struct net *net, struct ppp_file *pf, 
		spin_lock_bh(&pn->all_channels_lock);

		chan = ppp_find_channel(pn, unit);

		if (chan) {

			atomic_inc(&chan->file.refcnt);

			refcount_inc(&chan->file.refcnt);

			file->private_data = &chan->file;

			err = 0;

		}
@@ -1348,7 +1349,7 @@ static int ppp_dev_init(struct net_device *dev) 
	 * that ppp_destroy_interface() won't run before the device gets

	 * unregistered.

	 */

	atomic_inc(&ppp->file.refcnt);

	refcount_inc(&ppp->file.refcnt);



	return 0;

}
@@ -1377,7 +1378,7 @@ static void ppp_dev_priv_destructor(struct net_device *dev) 
	struct ppp *ppp;



	ppp = netdev_priv(dev);

	if (atomic_dec_and_test(&ppp->file.refcnt))

	if (refcount_dec_and_test(&ppp->file.refcnt))

		ppp_destroy_interface(ppp);

}
@@ -2676,7 +2677,7 @@ ppp_unregister_channel(struct ppp_channel *chan) 


	pch->file.dead = 1;

	wake_up_interruptible(&pch->file.rwait);

	if (atomic_dec_and_test(&pch->file.refcnt))

	if (refcount_dec_and_test(&pch->file.refcnt))

		ppp_destroy_channel(pch);

}
@@ -3046,7 +3047,7 @@ init_ppp_file(struct ppp_file *pf, int kind) 
	pf->kind = kind;

	skb_queue_head_init(&pf->xq);

	skb_queue_head_init(&pf->rq);

	atomic_set(&pf->refcnt, 1);

	refcount_set(&pf->refcnt, 1);

	init_waitqueue_head(&pf->rwait);

}
@@ -3164,7 +3165,7 @@ ppp_connect_channel(struct channel *pch, int unit) 
	list_add_tail(&pch->clist, &ppp->channels);

	++ppp->n_channels;

	pch->ppp = ppp;

	atomic_inc(&ppp->file.refcnt);

	refcount_inc(&ppp->file.refcnt);

	ppp_unlock(ppp);

	ret = 0;
@@ -3195,7 +3196,7 @@ ppp_disconnect_channel(struct channel *pch) 
		if (--ppp->n_channels == 0)

			wake_up_interruptible(&ppp->file.rwait);

		ppp_unlock(ppp);

		if (atomic_dec_and_test(&ppp->file.refcnt))

		if (refcount_dec_and_test(&ppp->file.refcnt))

			ppp_destroy_interface(ppp);

		err = 0;

	}