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virtio-balloon: fix integer overflow in BALLOON_CHANGE QMP event 

Because dev->actual is uint32_t, the expression 'dev->actual <<
VIRTIO_BALLOON_PFN_SHIFT' is truncated to 32 bits. This overflows when
dev->actual >= 1048576.

To reproduce:

 1. Start a VM with a QMP socket and 5G of RAM
 2. Connect to the QMP socket, negotiate capabilities and issue:

   { "execute":"balloon", "arguments": { "value": 1073741824 } }

 3. Watch for BALLOON_CHANGE QMP events, the last one will incorretly be:

   { "timestamp": { "seconds": 1366228965, "microseconds": 245466 },
     "event": "BALLOON_CHANGE", "data": { "actual": 5368709120 } }

To fix it this commit casts it to ram_addr_t, which is ram_size's type.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Luiz Capitulino 2013-04-18 11:53:32 -04:00
parent 153d02e338
commit dcc6ceffc0
1 changed files with 1 additions and 1 deletions
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2
hw/virtio/virtio-balloon.c
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@ -275,7 +275,7 @@ static void virtio_balloon_set_config(VirtIODevice *vdev,
dev->actual = le32_to_cpu(config.actual);
if (dev->actual != oldactual) {
qemu_balloon_changed(ram_size -
(dev->actual << VIRTIO_BALLOON_PFN_SHIFT));
((ram_addr_t) dev->actual << VIRTIO_BALLOON_PFN_SHIFT));
}
}