path: root/drivers
diff options
authorElena Reshetova <elena.reshetova@intel.com>2017-10-20 10:23:48 +0300
committerDavid S. Miller <davem@davemloft.net>2017-10-22 02:22:39 +0100
commit709c89b45b874b2f81a074b8802a736009873f48 (patch)
tree80ef98e8c9744487746d29eb1313d39762a08ac8 /drivers
parentd780cd44e3cea119a3346e6d7c04d35b9c50d54b (diff)
drivers, net, ppp: convert syncppp.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 syncppp.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>
Diffstat (limited to 'drivers')
1 files changed, 6 insertions, 5 deletions
diff --git a/drivers/net/ppp/ppp_synctty.c b/drivers/net/ppp/ppp_synctty.c
index 7868c29071d4..7196f00f0991 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)
ap = tty->disc_data;
if (ap != NULL)
- atomic_inc(&ap->refcnt);
+ refcount_inc(&ap->refcnt);
return ap;
static void sp_put(struct syncppp *ap)
- if (atomic_dec_and_test(&ap->refcnt))
+ if (refcount_dec_and_test(&ap->refcnt))
@@ -182,7 +183,7 @@ ppp_sync_open(struct tty_struct *tty)
tasklet_init(&ap->tsk, ppp_sync_process, (unsigned long) ap);
- atomic_set(&ap->refcnt, 1);
+ refcount_set(&ap->refcnt, 1);
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))

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