From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752746AbdBTLhW (ORCPT ); Mon, 20 Feb 2017 06:37:22 -0500 Received: from mail-wr0-f196.google.com ([209.85.128.196]:36236 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751357AbdBTLhT (ORCPT ); Mon, 20 Feb 2017 06:37:19 -0500 Subject: Re: [PATCH 4/4] kvm: convert kvm.users_count from atomic_t to refcount_t To: Elena Reshetova , linux-kernel@vger.kernel.org References: <1487588781-15123-1-git-send-email-elena.reshetova@intel.com> <1487588781-15123-5-git-send-email-elena.reshetova@intel.com> 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, Hans Liljestrand , Kees Cook , David Windsor From: Paolo Bonzini Message-ID: <220f229f-0e3e-2a72-62c1-1677021c3987@redhat.com> Date: Mon, 20 Feb 2017 12:37:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <1487588781-15123-5-git-send-email-elena.reshetova@intel.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20/02/2017 12:06, Elena Reshetova wrote: > 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 Looks good, will apply after the merge window. Paolo > --- > 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)) { >