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Subject[PATCH 13/16] drivers, net, ppp: convert ppp_file.refcnt from atomic_t to refcount_t
Date
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>
---
drivers/net/ppp/ppp_generic.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index f9c0e62..7b1352c 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -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 */
@@ -407,7 +408,7 @@ 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));
@@ -880,7 +881,7 @@ 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;
}
@@ -895,7 +896,7 @@ 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;
}
@@ -2641,7 +2642,7 @@ 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);
}

@@ -3011,7 +3012,7 @@ 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);
}

@@ -3128,7 +3129,7 @@ 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;

@@ -3159,7 +3160,7 @@ 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;
}
--
2.7.4
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