Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932202AbdHYJm3 (ORCPT ); Fri, 25 Aug 2017 05:42:29 -0400 Received: from mga04.intel.com ([192.55.52.120]:13015 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932144AbdHYJm1 (ORCPT ); Fri, 25 Aug 2017 05:42:27 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,424,1498546800"; d="scan'208";a="893999777" 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 10/15] uprobes: convert uprobe.ref to refcount_t Date: Fri, 25 Aug 2017 12:41:27 +0300 Message-Id: <1503654092-15471-11-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1503654092-15471-1-git-send-email-elena.reshetova@intel.com> References: <1503654092-15471-1-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: 2173 Lines: 65 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 uprobe.ref 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/uprobes.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 456596d..ca093957 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -66,7 +66,7 @@ static struct percpu_rw_semaphore dup_mmap_sem; struct uprobe { struct rb_node rb_node; /* node in the rb tree */ - atomic_t ref; + refcount_t ref; struct rw_semaphore register_rwsem; struct rw_semaphore consumer_rwsem; struct list_head pending_list; @@ -371,13 +371,13 @@ set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long v static struct uprobe *get_uprobe(struct uprobe *uprobe) { - atomic_inc(&uprobe->ref); + refcount_inc(&uprobe->ref); return uprobe; } static void put_uprobe(struct uprobe *uprobe) { - if (atomic_dec_and_test(&uprobe->ref)) + if (refcount_dec_and_test(&uprobe->ref)) kfree(uprobe); } @@ -459,7 +459,7 @@ static struct uprobe *__insert_uprobe(struct uprobe *uprobe) rb_link_node(&uprobe->rb_node, parent, p); rb_insert_color(&uprobe->rb_node, &uprobes_tree); /* get access + creation ref */ - atomic_set(&uprobe->ref, 2); + refcount_set(&uprobe->ref, 2); return u; } -- 2.7.4