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Subject[PATCH 12/16] drivers, net, ppp: convert asyncppp.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_async.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ppp/ppp_async.c b/drivers/net/ppp/ppp_async.c
index feb9569..2d08f7e 100644
--- a/drivers/net/ppp/ppp_async.c
+++ b/drivers/net/ppp/ppp_async.c
@@ -69,7 +69,7 @@ struct asyncppp {

struct tasklet_struct tsk;

- atomic_t refcnt;
+ refcount_t refcnt;
struct semaphore dead_sem;
struct ppp_channel chan; /* interface to generic ppp layer */
unsigned char obuf[OBUFSIZE];
@@ -140,14 +140,14 @@ static struct asyncppp *ap_get(struct tty_struct *tty)
read_lock(&disc_data_lock);
ap = tty->disc_data;
if (ap != NULL)
- atomic_inc(&ap->refcnt);
+ refcount_inc(&ap->refcnt);
read_unlock(&disc_data_lock);
return ap;
}

static void ap_put(struct asyncppp *ap)
{
- if (atomic_dec_and_test(&ap->refcnt))
+ if (refcount_dec_and_test(&ap->refcnt))
up(&ap->dead_sem);
}

@@ -185,7 +185,7 @@ ppp_asynctty_open(struct tty_struct *tty)
skb_queue_head_init(&ap->rqueue);
tasklet_init(&ap->tsk, ppp_async_process, (unsigned long) ap);

- atomic_set(&ap->refcnt, 1);
+ refcount_set(&ap->refcnt, 1);
sema_init(&ap->dead_sem, 0);

ap->chan.private = ap;
@@ -234,7 +234,7 @@ ppp_asynctty_close(struct tty_struct *tty)
* our channel ops (i.e. ppp_async_send/ioctl) are in progress
* by the time it returns.
*/
- if (!atomic_dec_and_test(&ap->refcnt))
+ if (!refcount_dec_and_test(&ap->refcnt))
down(&ap->dead_sem);
tasklet_kill(&ap->tsk);

--
2.7.4
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