Re: [Qemu-devel] [PATCH v2 14/18] nvdimm: support NFIT_CMD_IMPLEMENTED function

[Stefan Hajnoczi]

On Wed, Aug 26, 2015 at 06:46:35PM +0800, Xiao Guangrong wrote:
> On 08/26/2015 12:23 AM, Stefan Hajnoczi wrote:
> >On Fri, Aug 14, 2015 at 10:52:07PM +0800, Xiao Guangrong wrote:
> >>  static void dsm_write(void *opaque, hwaddr addr,
> >>                        uint64_t val, unsigned size)
> >>  {
> >>+    struct MemoryRegion *dsm_ram_mr = opaque;
> >>+    struct dsm_buffer *dsm;
> >>+    struct dsm_out *out;
> >>+    void *buf;
> >>+
> >>      assert(val == NOTIFY_VALUE);
> >
> >The guest should not be able to cause an abort(3).  If val !=
> >NOTIFY_VALUE we can do nvdebug() and then return.
> 
> The ACPI code and emulation code both are from qemu, if that happens,
> it's really a bug, aborting the VM is better than throwing a debug
> message under this case to avoid potential data corruption.

abort(3) is dangerous because it can create a core dump.  If a malicious
guest triggers this repeatedly it could consume a lot of disk space and
I/O or CPU while performing the core dumps.

We cannot trust anything inside the guest, even if the guest code comes
from QEMU because a malicious guest can still read/write to the same
hardware registers.

Stefan