From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752915AbdBTLGs (ORCPT ); Mon, 20 Feb 2017 06:06:48 -0500 Received: from mga02.intel.com ([134.134.136.20]:57934 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751436AbdBTLGp (ORCPT ); Mon, 20 Feb 2017 06:06:45 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.35,186,1484035200"; d="scan'208";a="826325806" From: Elena Reshetova To: linux-kernel@vger.kernel.org Cc: linux-edac@vger.kernel.org, x86@kernel.org, sparclinux@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, peterz@infradead.org, gregkh@linuxfoundation.org, davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, tony.luck@intel.com, hpa@zytor.com, Elena Reshetova , Hans Liljestrand , Kees Cook , David Windsor Subject: [PATCH 4/4] kvm: convert kvm.users_count from atomic_t to refcount_t Date: Mon, 20 Feb 2017 13:06:21 +0200 Message-Id: <1487588781-15123-5-git-send-email-elena.reshetova@intel.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1487588781-15123-1-git-send-email-elena.reshetova@intel.com> References: <1487588781-15123-1-git-send-email-elena.reshetova@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org refcount_t type and corresponding API should be used instead of atomic_t when the variable is used as a reference counter. This allows to avoid accidental refcounter overflows that might lead to use-after-free situations. Signed-off-by: Elena Reshetova Signed-off-by: Hans Liljestrand Signed-off-by: Kees Cook Signed-off-by: David Windsor --- include/linux/kvm_host.h | 3 ++- virt/kvm/kvm_main.c | 8 ++++---- 2 files changed, 6 insertions(+), 5 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index cda457b..7fa05a5 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -26,6 +26,7 @@ #include #include #include +#include #include #include @@ -402,7 +403,7 @@ struct kvm { #endif struct kvm_vm_stat stat; struct kvm_arch arch; - atomic_t users_count; + refcount_t users_count; #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET struct kvm_coalesced_mmio_ring *coalesced_mmio_ring; spinlock_t ring_lock; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index dcd1c12..6ae5775 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -622,7 +622,7 @@ static struct kvm *kvm_create_vm(unsigned long type) mutex_init(&kvm->lock); mutex_init(&kvm->irq_lock); mutex_init(&kvm->slots_lock); - atomic_set(&kvm->users_count, 1); + refcount_set(&kvm->users_count, 1); INIT_LIST_HEAD(&kvm->devices); r = kvm_arch_init_vm(kvm, type); @@ -745,13 +745,13 @@ static void kvm_destroy_vm(struct kvm *kvm) void kvm_get_kvm(struct kvm *kvm) { - atomic_inc(&kvm->users_count); + refcount_inc(&kvm->users_count); } EXPORT_SYMBOL_GPL(kvm_get_kvm); void kvm_put_kvm(struct kvm *kvm) { - if (atomic_dec_and_test(&kvm->users_count)) + if (refcount_dec_and_test(&kvm->users_count)) kvm_destroy_vm(kvm); } EXPORT_SYMBOL_GPL(kvm_put_kvm); @@ -3640,7 +3640,7 @@ static int kvm_debugfs_open(struct inode *inode, struct file *file, * To avoid the race between open and the removal of the debugfs * directory we test against the users count. */ - if (!atomic_add_unless(&stat_data->kvm->users_count, 1, 0)) + if (!refcount_inc_not_zero(&stat_data->kvm->users_count)) return -ENOENT; if (simple_attr_open(inode, file, get, set, fmt)) { -- 2.7.4