From e3736c3eb3a6f7c0966923b629c9f92b558aa9c7 Mon Sep 17 00:00:00 2001
From: Elena Reshetova <elena.reshetova@intel.com>
Date: Mon, 20 Feb 2017 13:06:21 +0200
Subject: [PATCH] kvm: convert kvm.users_count from atomic_t to refcount_t
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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 <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
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 8d69d51507483..2c14ad9809da9 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -26,6 +26,7 @@
#include <linux/context_tracking.h>
#include <linux/irqbypass.h>
#include <linux/swait.h>
+#include <linux/refcount.h>
#include <asm/signal.h>
#include <linux/kvm.h>
@@ -401,7 +402,7 @@ 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 cc4d6e0dd2a23..c6b7aff634bec 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -617,7 +617,7 @@ 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);
@@ -747,13 +747,13 @@ 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);
@@ -3639,7 +3639,7 @@ 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)) {