lkml.org 
[lkml]   [2019]   [Jul]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/6] vhost: validate MMU notifier registration
Date
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(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 34c0d970bcbc..058191d5efad 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -630,6 +630,7 @@ 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);
@@ -731,6 +732,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
if (err)
goto err_mmu_notifier;
#endif
+ dev->has_notifier = true;

return 0;

@@ -960,7 +962,11 @@ 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);
}
@@ -2065,8 +2071,10 @@ 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
@@ -2086,8 +2094,11 @@ 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);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 819296332913..a62f56a4cf72 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -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);
--
2.18.1
\
 
 \ /
  Last update: 2019-07-23 09:59    [W:0.097 / U:0.692 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site