@@ -629,6 +629,7 @@ void vhost_dev_init(struct vhost_dev *dev,
dev->iov_limit = iov_limit;
dev->weight = weight;
dev->byte_weight = byte_weight;
+ dev->has_notifier = false;
init_llist_head(&dev->work_list);
init_waitqueue_head(&dev->wait);
INIT_LIST_HEAD(&dev->read_list);
@@ -730,6 +731,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
if (err)
goto err_mmu_notifier;
#endif
+ dev->has_notifier = true;
return 0;
@@ -959,7 +961,11 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
}
if (dev->mm) {
#if VHOST_ARCH_CAN_ACCEL_UACCESS
- mmu_notifier_unregister(&dev->mmu_notifier, dev->mm);
+ if (dev->has_notifier) {
+ mmu_notifier_unregister(&dev->mmu_notifier,
+ dev->mm);
+ dev->has_notifier = false;
+ }
#endif
mmput(dev->mm);
}
@@ -2064,8 +2070,10 @@ static long vhost_vring_set_num_addr(struct vhost_dev *d,
/* Unregister MMU notifer to allow invalidation callback
* can access vq->uaddrs[] without holding a lock.
*/
- if (d->mm)
+ if (d->has_notifier) {
mmu_notifier_unregister(&d->mmu_notifier, d->mm);
+ d->has_notifier = false;
+ }
vhost_uninit_vq_maps(vq);
#endif
@@ -2085,8 +2093,11 @@ static long vhost_vring_set_num_addr(struct vhost_dev *d,
if (r == 0)
vhost_setup_vq_uaddr(vq);
- if (d->mm)
- mmu_notifier_register(&d->mmu_notifier, d->mm);
+ if (d->mm) {
+ r = mmu_notifier_register(&d->mmu_notifier, d->mm);
+ if (!r)
+ d->has_notifier = true;
+ }
#endif
mutex_unlock(&vq->mutex);
@@ -214,6 +214,7 @@ struct vhost_dev {
int iov_limit;
int weight;
int byte_weight;
+ bool has_notifier;
};
bool vhost_exceeds_weight(struct vhost_virtqueue *vq, int pkts, int total_len);
The return value of mmu_notifier_register() is not checked in vhost_vring_set_num_addr(). This will cause an out of sync between mm and MMU notifier thus a double free. To solve this, introduce a boolean flag to track whether MMU notifier is registered and only do unregistering when it was true. Reported-and-tested-by: syzbot+e58112d71f77113ddb7b@syzkaller.appspotmail.com Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address") Signed-off-by: Jason Wang <jasowang@redhat.com> --- drivers/vhost/vhost.c | 19 +++++++++++++++---- drivers/vhost/vhost.h | 1 + 2 files changed, 16 insertions(+), 4 deletions(-)