From mboxrd@z Thu Jan 1 00:00:00 1970 From: Elena Reshetova Date: Fri, 20 Oct 2017 07:23:46 +0000 Subject: [PATCH 12/15] drivers, net, ppp: convert asyncppp.refcnt from atomic_t to refcount_t Message-Id: <1508484229-19706-13-git-send-email-elena.reshetova@intel.com> List-Id: References: <1508484229-19706-1-git-send-email-elena.reshetova@intel.com> In-Reply-To: <1508484229-19706-1-git-send-email-elena.reshetova@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: davem@davemloft.net Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-rdma@vger.kernel.org, linux-hams@vger.kernel.org, linux-ppp@vger.kernel.org, ganeshgr@chelsio.com, nbd@openwrt.org, john@phrozen.org, sean.wang@mediatek.com, matthias.bgg@gmail.com, yishaih@mellanox.com, saeedm@mellanox.com, matanb@mellanox.com, tariqt@mellanox.com, leonro@mellanox.com, ajk@comnets.uni-bremen.de, paulus@samba.org, zbr@ioremap.net, peterz@infradead.org, keescook@chromium.org, Elena Reshetova 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 Reviewed-by: David Windsor Reviewed-by: Hans Liljestrand Signed-off-by: Elena Reshetova --- 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 814fd8f..1b28e6e 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