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Subject[PATCH 14/16] drivers, net, ppp: convert syncppp.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_synctty.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c
index 9ae5398..4a643f8 100644
--- a/drivers/net/ppp/ppp_synctty.c
+++ b/drivers/net/ppp/ppp_synctty.c
@@ -46,6 +46,7 @@
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
+#include <linux/refcount.h>
#include <asm/unaligned.h>
#include <linux/uaccess.h>

@@ -72,7 +73,7 @@ struct syncppp {

struct tasklet_struct tsk;

- atomic_t refcnt;
+ refcount_t refcnt;
struct completion dead_cmp;
struct ppp_channel chan; /* interface to generic ppp layer */
};
@@ -141,14 +142,14 @@ static struct syncppp *sp_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 sp_put(struct syncppp *ap)
{
- if (atomic_dec_and_test(&ap->refcnt))
+ if (refcount_dec_and_test(&ap->refcnt))
complete(&ap->dead_cmp);
}

@@ -182,7 +183,7 @@ ppp_sync_open(struct tty_struct *tty)
skb_queue_head_init(&ap->rqueue);
tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap);

- atomic_set(&ap->refcnt, 1);
+ refcount_set(&ap->refcnt, 1);
init_completion(&ap->dead_cmp);

ap->chan.private = ap;
@@ -232,7 +233,7 @@ ppp_sync_close(struct tty_struct *tty)
* our channel ops (i.e. ppp_sync_send/ioctl) are in progress
* by the time it returns.
*/
- if (!atomic_dec_and_test(&ap->refcnt))
+ if (!refcount_dec_and_test(&ap->refcnt))
wait_for_completion(&ap->dead_cmp);
tasklet_kill(&ap->tsk);

--
2.7.4
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