Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751752AbdH3MXr (ORCPT ); Wed, 30 Aug 2017 08:23:47 -0400 Received: from mga06.intel.com ([134.134.136.31]:21550 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751717AbdH3MXm (ORCPT ); Wed, 30 Aug 2017 08:23:42 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,448,1498546800"; d="scan'208";a="895512178" From: Elena Reshetova To: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, tj@kernel.org, mingo@redhat.com, hannes@cmpxchg.org, lizefan@huawei.com, acme@kernel.org, alexander.shishkin@linux.intel.com, eparis@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, luto@kernel.org, keescook@chromium.org, tglx@linutronix.de, dvhart@infradead.org, ebiederm@xmission.com, Elena Reshetova Subject: [PATCH 08/15] perf/ring_buffer: convert ring_buffer.refcount to refcount_t Date: Wed, 30 Aug 2017 15:22:46 +0300 Message-Id: <1504095773-22895-9-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1504095773-22895-1-git-send-email-elena.reshetova@intel.com> References: <1504095773-22895-1-git-send-email-elena.reshetova@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2742 Lines: 84 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 ring_buffer.refcount 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 --- kernel/events/core.c | 4 ++-- kernel/events/internal.h | 3 ++- kernel/events/ring_buffer.c | 2 +- 3 files changed, 5 insertions(+), 4 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 57ef7ce..43da16ef 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5089,7 +5089,7 @@ struct ring_buffer *ring_buffer_get(struct perf_event *event) rcu_read_lock(); rb = rcu_dereference(event->rb); if (rb) { - if (!atomic_inc_not_zero(&rb->refcount)) + if (!refcount_inc_not_zero(&rb->refcount)) rb = NULL; } rcu_read_unlock(); @@ -5099,7 +5099,7 @@ struct ring_buffer *ring_buffer_get(struct perf_event *event) void ring_buffer_put(struct ring_buffer *rb) { - if (!atomic_dec_and_test(&rb->refcount)) + if (!refcount_dec_and_test(&rb->refcount)) return; WARN_ON_ONCE(!list_empty(&rb->event_list)); diff --git a/kernel/events/internal.h b/kernel/events/internal.h index 486fd78..b8e6fdf 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -3,13 +3,14 @@ #include #include +#include /* Buffer handling */ #define RING_BUFFER_WRITABLE 0x01 struct ring_buffer { - atomic_t refcount; + refcount_t refcount; struct rcu_head rcu_head; #ifdef CONFIG_PERF_USE_VMALLOC struct work_struct work; diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index ee97196..3353572 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -284,7 +284,7 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) else rb->overwrite = 1; - atomic_set(&rb->refcount, 1); + refcount_set(&rb->refcount, 1); INIT_LIST_HEAD(&rb->event_list); spin_lock_init(&rb->event_lock); -- 2.7.4