From ae6959273a29426813974211e41e28f495bc10a6 Mon Sep 17 00:00:00 2001 From: Elena Reshetova Date: Wed, 20 Dec 2017 20:10:56 +0100 Subject: [PATCH] qeth: convert qeth_reply.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 qeth_reply.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 [jwi: removed the WARN_ONs. Use CONFIG_REFCOUNT_FULL if you care.] Signed-off-by: Julian Wiedmann Signed-off-by: David S. Miller --- drivers/s390/net/qeth_core.h | 3 ++- drivers/s390/net/qeth_core_main.c | 8 +++----- 2 files changed, 5 insertions(+), 6 deletions(-) diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h index badf42acbf95..f5ee62c98011 100644 --- a/drivers/s390/net/qeth_core.h +++ b/drivers/s390/net/qeth_core.h @@ -21,6 +21,7 @@ #include #include #include +#include #include #include @@ -632,7 +633,7 @@ struct qeth_reply { int rc; void *param; struct qeth_card *card; - atomic_t refcnt; + refcount_t refcnt; }; struct qeth_card_blkt { diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c index 6c815207f4f5..bc4e57540a9e 100644 --- a/drivers/s390/net/qeth_core_main.c +++ b/drivers/s390/net/qeth_core_main.c @@ -564,7 +564,7 @@ static struct qeth_reply *qeth_alloc_reply(struct qeth_card *card) reply = kzalloc(sizeof(struct qeth_reply), GFP_ATOMIC); if (reply) { - atomic_set(&reply->refcnt, 1); + refcount_set(&reply->refcnt, 1); atomic_set(&reply->received, 0); reply->card = card; } @@ -573,14 +573,12 @@ static struct qeth_reply *qeth_alloc_reply(struct qeth_card *card) static void qeth_get_reply(struct qeth_reply *reply) { - WARN_ON(atomic_read(&reply->refcnt) <= 0); - atomic_inc(&reply->refcnt); + refcount_inc(&reply->refcnt); } static void qeth_put_reply(struct qeth_reply *reply) { - WARN_ON(atomic_read(&reply->refcnt) <= 0); - if (atomic_dec_and_test(&reply->refcnt)) + if (refcount_dec_and_test(&reply->refcnt)) kfree(reply); }