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kvm: convert kvm.users_count from atomic_t to refcount_t 

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>
This commit is contained in:
Elena Reshetova 2017-02-20 13:06:21 +02:00 committed by Radim Krčmář
parent bba82fd756
commit e3736c3eb3
2 changed files with 6 additions and 5 deletions
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3
include/linux/kvm_host.h
View File

@ -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;

8
virt/kvm/kvm_main.c
View File

@ -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)) {