Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit e3736c3e authored by Elena Reshetova's avatar Elena Reshetova Committed by Radim Krčmář
Browse files

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: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarDavid Windsor <dwindsor@gmail.com>
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
parent bba82fd7

include/linux/kvm_host.h

+2 −1
Original line number Diff line number Diff line
@@ -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;

virt/kvm/kvm_main.c

+4 −4
Original line number Diff line number Diff line
@@ -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)) {