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 <elena.reshetova@xxxxxxxxx>
> Signed-off-by: Hans Liljestrand <ishkamiel@xxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Signed-off-by: David Windsor <dwindsor@xxxxxxxxx>
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 <linux/context_tracking.h>
> #include <linux/irqbypass.h>
> #include <linux/swait.h>
> +#include <linux/refcount.h>
> #include <asm/signal.h>
>
> #include <linux/kvm.h>
> @@ -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)) {
>
