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From 8c80943cfe6e8e50f0a18cc2b4f09f9eefed47dc Mon Sep 17 00:00:00 2001
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Date: Tue, 26 Nov 2019 16:29:02 +0000
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Subject: [PATCH 16/16] vhost: fix vhost_log size overflow during migration
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RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Message-id: <20191126162902.46145-2-dgilbert@redhat.com>
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Patchwork-id: 92689
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O-Subject: [RHEL-AV-8.2.0 qemu-kvm PATCH 1/1] vhost: fix vhost_log size overflow during migration
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Bugzilla: 1776808
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RH-Acked-by: Peter Xu <peterx@redhat.com>
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
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From: Li Hangjing <lihangjing@baidu.com>
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When a guest which doesn't support multiqueue is migrated with a multi queues
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vhost-user-blk deivce, a crash will occur like:
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0 qemu_memfd_alloc (name=<value optimized out>, size=562949953421312, seals=<value optimized out>, fd=0x7f87171fe8b4, errp=0x7f87171fe8a8) at util/memfd.c:153
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1 0x00007f883559d7cf in vhost_log_alloc (size=70368744177664, share=true) at hw/virtio/vhost.c:186
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2 0x00007f88355a0758 in vhost_log_get (listener=0x7f8838bd7940, enable=1) at qemu-2-12/hw/virtio/vhost.c:211
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3 vhost_dev_log_resize (listener=0x7f8838bd7940, enable=1) at hw/virtio/vhost.c:263
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4 vhost_migration_log (listener=0x7f8838bd7940, enable=1) at hw/virtio/vhost.c:787
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5 0x00007f88355463d6 in memory_global_dirty_log_start () at memory.c:2503
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6 0x00007f8835550577 in ram_init_bitmaps (f=0x7f88384ce600, opaque=0x7f8836024098) at migration/ram.c:2173
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7 ram_init_all (f=0x7f88384ce600, opaque=0x7f8836024098) at migration/ram.c:2192
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8 ram_save_setup (f=0x7f88384ce600, opaque=0x7f8836024098) at migration/ram.c:2219
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9 0x00007f88357a419d in qemu_savevm_state_setup (f=0x7f88384ce600) at migration/savevm.c:1002
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10 0x00007f883579fc3e in migration_thread (opaque=0x7f8837530400) at migration/migration.c:2382
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11 0x00007f8832447893 in start_thread () from /lib64/libpthread.so.0
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12 0x00007f8832178bfd in clone () from /lib64/libc.so.6
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This is because vhost_get_log_size() returns a overflowed vhost-log size.
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In this function, it uses the uninitialized variable vqs->used_phys and
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vqs->used_size to get the vhost-log size.
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Signed-off-by: Li Hangjing <lihangjing@baidu.com>
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Reviewed-by: Xie Yongji <xieyongji@baidu.com>
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Reviewed-by: Chai Wen <chaiwen@baidu.com>
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Message-Id: <20190603061524.24076-1-lihangjing@baidu.com>
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Cc: qemu-stable@nongnu.org
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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(cherry picked from commit 240e647a14df9677b3a501f7b8b870e40aac3fd5)
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 hw/virtio/vhost.c | 10 ++++++++++
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 1 file changed, 10 insertions(+)
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diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
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index 1ae68ff..7bdc9c4 100644
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--- a/hw/virtio/vhost.c
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+++ b/hw/virtio/vhost.c
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@@ -131,6 +131,11 @@ static int vhost_sync_dirty_bitmap(struct vhost_dev *dev,
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     }
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     for (i = 0; i < dev->nvqs; ++i) {
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         struct vhost_virtqueue *vq = dev->vqs + i;
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+
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+        if (!vq->used_phys && !vq->used_size) {
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+            continue;
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+        }
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+
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         vhost_dev_sync_region(dev, section, start_addr, end_addr, vq->used_phys,
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                               range_get_last(vq->used_phys, vq->used_size));
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     }
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@@ -168,6 +173,11 @@ static uint64_t vhost_get_log_size(struct vhost_dev *dev)
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     }
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     for (i = 0; i < dev->nvqs; ++i) {
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         struct vhost_virtqueue *vq = dev->vqs + i;
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+
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+        if (!vq->used_phys && !vq->used_size) {
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+            continue;
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+        }
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+
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         uint64_t last = vq->used_phys + vq->used_size - 1;
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         log_size = MAX(log_size, last / VHOST_LOG_CHUNK + 1);
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     }
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-- 
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1.8.3.1
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