Re: [Qemu-devel] [PULL 23/35] x86: ioapic: dump version for "info ioapic"

[Peter Maydell]

On 20 January 2017 at 13:31, Paolo Bonzini <address@hidden> wrote:
> From: Peter Xu <address@hidden>
>
> Signed-off-by: Peter Xu <address@hidden>
> Message-Id: <address@hidden>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  hw/intc/ioapic_common.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/hw/intc/ioapic_common.c b/hw/intc/ioapic_common.c
> index 1b7ec5e..97c4f9c 100644
> --- a/hw/intc/ioapic_common.c
> +++ b/hw/intc/ioapic_common.c
> @@ -58,7 +58,8 @@ void ioapic_print_redtbl(Monitor *mon, IOAPICCommonState *s)
>      uint32_t remote_irr = 0;
>      int i;
>
> -    monitor_printf(mon, "ioapic id=0x%02x sel=0x%02x", s->id, s->ioregsel);
> +    monitor_printf(mon, "ioapic ver=0x%x id=0x%02x sel=0x%02x",
> +                   s->version, s->id, s->ioregsel);
>      if (s->ioregsel) {
>          monitor_printf(mon, " (redir[%u])\n",
>                         (s->ioregsel - IOAPIC_REG_REDTBL_BASE) >> 1);

Coverity points out (CID 1369422) that this is a use of a possibly
uninitialized field. In kvm_ioapic_dump_state() we do:

    IOAPICCommonState s;
    kvm_ioapic_get(&s);
    ioapic_print_redtbl(mon, &s);

and kvm_ioapic_get() doesn't initialize s->version, so when we
come to print it in ioapic_print_redtbl() it's uninitialized.

The easy fix is to initialize version to something. The
underlying problem here I think is that we're manufacturing
a fake IOAPICCommonState rather than finding the one that
corresponds to the actual IOAPIC device in the system...

thanks
-- PMM