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author | Elena Reshetova <elena.reshetova@intel.com> | 2017-10-20 10:23:46 +0300 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2017-10-22 02:22:39 +0100 |
commit | 313a912155c78ed87ad6fca175dc56b75fd00a58 (patch) | |
tree | 265fd14a918c1eddf6799edd2f7981bbb5658d2f | |
parent | 28206cdb3bc079a97d24c33b4427395f9e406fad (diff) | |
download | linux-stable-313a912155c78ed87ad6fca175dc56b75fd00a58.tar.gz linux-stable-313a912155c78ed87ad6fca175dc56b75fd00a58.tar.bz2 linux-stable-313a912155c78ed87ad6fca175dc56b75fd00a58.zip |
drivers, net, ppp: convert asyncppp.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 asyncppp.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>
-rw-r--r-- | drivers/net/ppp/ppp_async.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/net/ppp/ppp_async.c b/drivers/net/ppp/ppp_async.c index 814fd8fae67d..1b28e6e702f5 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); |