From 8c80943cfe6e8e50f0a18cc2b4f09f9eefed47dc Mon Sep 17 00:00:00 2001

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Date: Tue, 26 Nov 2019 16:29:02 +0000

Subject: [PATCH 16/16] vhost: fix vhost_log size overflow during migration

RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>

Message-id: <20191126162902.46145-2-dgilbert@redhat.com>

Patchwork-id: 92689

O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH 1/1] vhost: fix vhost_log size overflow during migration

Bugzilla: 1776808

RH-Acked-by: Peter Xu <peterx@redhat.com>

RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>

From: Li Hangjing <lihangjing@baidu.com>

When a guest which doesn't support multiqueue is migrated with a multi queues

vhost-user-blk deivce, a crash will occur like:

0 qemu_memfd_alloc (name=<value optimized out>, size=562949953421312, seals=<value optimized out>, fd=0x7f87171fe8b4, errp=0x7f87171fe8a8) at util/memfd.c:153

1 0x00007f883559d7cf in vhost_log_alloc (size=70368744177664, share=true) at hw/virtio/vhost.c:186

2 0x00007f88355a0758 in vhost_log_get (listener=0x7f8838bd7940, enable=1) at qemu-2-12/hw/virtio/vhost.c:211

3 vhost_dev_log_resize (listener=0x7f8838bd7940, enable=1) at hw/virtio/vhost.c:263

4 vhost_migration_log (listener=0x7f8838bd7940, enable=1) at hw/virtio/vhost.c:787

5 0x00007f88355463d6 in memory_global_dirty_log_start () at memory.c:2503

6 0x00007f8835550577 in ram_init_bitmaps (f=0x7f88384ce600, opaque=0x7f8836024098) at migration/ram.c:2173

7 ram_init_all (f=0x7f88384ce600, opaque=0x7f8836024098) at migration/ram.c:2192

8 ram_save_setup (f=0x7f88384ce600, opaque=0x7f8836024098) at migration/ram.c:2219

9 0x00007f88357a419d in qemu_savevm_state_setup (f=0x7f88384ce600) at migration/savevm.c:1002

10 0x00007f883579fc3e in migration_thread (opaque=0x7f8837530400) at migration/migration.c:2382

11 0x00007f8832447893 in start_thread () from /lib64/libpthread.so.0

12 0x00007f8832178bfd in clone () from /lib64/libc.so.6

This is because vhost_get_log_size() returns a overflowed vhost-log size.

In this function, it uses the uninitialized variable vqs->used_phys and

vqs->used_size to get the vhost-log size.

Signed-off-by: Li Hangjing <lihangjing@baidu.com>

Reviewed-by: Xie Yongji <xieyongji@baidu.com>

Reviewed-by: Chai Wen <chaiwen@baidu.com>

Message-Id: <20190603061524.24076-1-lihangjing@baidu.com>

Cc: qemu-stable@nongnu.org

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

(cherry picked from commit 240e647a14df9677b3a501f7b8b870e40aac3fd5)

Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>

---

 hw/virtio/vhost.c | 10 ++++++++++

 1 file changed, 10 insertions(+)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c

index 1ae68ff..7bdc9c4 100644

--- a/hw/virtio/vhost.c

+++ b/hw/virtio/vhost.c

@@ -131,6 +131,11 @@ static int vhost_sync_dirty_bitmap(struct vhost_dev *dev,

     }

     for (i = 0; i < dev->nvqs; ++i) {

         struct vhost_virtqueue *vq = dev->vqs + i;

+

+        if (!vq->used_phys && !vq->used_size) {

+            continue;

+        }

+

         vhost_dev_sync_region(dev, section, start_addr, end_addr, vq->used_phys,

                               range_get_last(vq->used_phys, vq->used_size));

     }

@@ -168,6 +173,11 @@ static uint64_t vhost_get_log_size(struct vhost_dev *dev)

     }

     for (i = 0; i < dev->nvqs; ++i) {

         struct vhost_virtqueue *vq = dev->vqs + i;

+

+        if (!vq->used_phys && !vq->used_size) {

+            continue;

+        }

+

         uint64_t last = vq->used_phys + vq->used_size - 1;

         log_size = MAX(log_size, last / VHOST_LOG_CHUNK + 1);

     }

-- 

1.8.3.1