* [PATCH V2] x86/monitor: Disallow setting mem_access_emulate_each_rep when vm_event is NULL
@ 2016-04-08 12:35 Razvan Cojocaru
2016-04-08 13:06 ` Andrew Cooper
0 siblings, 1 reply; 2+ messages in thread
From: Razvan Cojocaru @ 2016-04-08 12:35 UTC (permalink / raw)
To: xen-devel; +Cc: andrew.cooper3, keir, Razvan Cojocaru, jbeulich
It is meaningless (and potentially dangerous - see hvmemul_virtual_to_linear())
to set mem_access_emulate_each_rep before xc_monitor_enable() (which allocates
vcpu->arch.vm_event) has been called, so return an error from the
XEN_DOMCTL_MONITOR_OP_EMULATE_EACH_REP hypercall when that is the case.
Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
---
Changes since V1:
- Fixed the if() condition.
- Introduced an rc return variable to simplify the code.
---
xen/include/asm-x86/monitor.h | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
index 0954b59..a66760d 100644
--- a/xen/include/asm-x86/monitor.h
+++ b/xen/include/asm-x86/monitor.h
@@ -32,19 +32,29 @@
static inline
int arch_monitor_domctl_op(struct domain *d, struct xen_domctl_monitor_op *mop)
{
+ int rc = 0;
+
switch ( mop->op )
{
case XEN_DOMCTL_MONITOR_OP_EMULATE_EACH_REP:
domain_pause(d);
- d->arch.mem_access_emulate_each_rep = !!mop->event;
+ /*
+ * Enabling mem_access_emulate_each_rep without a vm_event subscriber
+ * is meaningless.
+ */
+ if ( d->vcpu && d->vcpu[0]->arch.vm_event )
+ d->arch.mem_access_emulate_each_rep = !!mop->event;
+ else
+ rc = -EINVAL;
+
domain_unpause(d);
break;
default:
- return -EOPNOTSUPP;
+ rc = -EOPNOTSUPP;
}
- return 0;
+ return rc;
}
int arch_monitor_domctl_event(struct domain *d,
--
1.9.1
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^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH V2] x86/monitor: Disallow setting mem_access_emulate_each_rep when vm_event is NULL
2016-04-08 12:35 [PATCH V2] x86/monitor: Disallow setting mem_access_emulate_each_rep when vm_event is NULL Razvan Cojocaru
@ 2016-04-08 13:06 ` Andrew Cooper
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Cooper @ 2016-04-08 13:06 UTC (permalink / raw)
To: Razvan Cojocaru, xen-devel; +Cc: keir, jbeulich
On 08/04/16 13:35, Razvan Cojocaru wrote:
> It is meaningless (and potentially dangerous - see hvmemul_virtual_to_linear())
> to set mem_access_emulate_each_rep before xc_monitor_enable() (which allocates
> vcpu->arch.vm_event) has been called, so return an error from the
> XEN_DOMCTL_MONITOR_OP_EMULATE_EACH_REP hypercall when that is the case.
>
> Signed-off-by: Razvan Cojocaru <rcojocaru@bitdefender.com>
>
> ---
> Changes since V1:
> - Fixed the if() condition.
> - Introduced an rc return variable to simplify the code.
> ---
> xen/include/asm-x86/monitor.h | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
> index 0954b59..a66760d 100644
> --- a/xen/include/asm-x86/monitor.h
> +++ b/xen/include/asm-x86/monitor.h
> @@ -32,19 +32,29 @@
> static inline
> int arch_monitor_domctl_op(struct domain *d, struct xen_domctl_monitor_op *mop)
> {
> + int rc = 0;
> +
> switch ( mop->op )
> {
> case XEN_DOMCTL_MONITOR_OP_EMULATE_EACH_REP:
> domain_pause(d);
> - d->arch.mem_access_emulate_each_rep = !!mop->event;
> + /*
> + * Enabling mem_access_emulate_each_rep without a vm_event subscriber
> + * is meaningless.
> + */
> + if ( d->vcpu && d->vcpu[0]->arch.vm_event )
Sorry - I forgot to mention this before, but this check is slightly
buggy. You want
if ( d->max_vcpus && d->vcpu[0] && d->vcpu[0]->arch.vm_event )
d->max_vcpus being non-zero guarentees that d->vcpu has been allocated,
but you still need to check that d->vcpu[0] has been allocated before
following the pointer.
With that fixed, Reviewed-by: Andrew Cooper <andrew.cooper3@citirx.com>
> + d->arch.mem_access_emulate_each_rep = !!mop->event;
> + else
> + rc = -EINVAL;
> +
> domain_unpause(d);
> break;
>
> default:
> - return -EOPNOTSUPP;
> + rc = -EOPNOTSUPP;
> }
>
> - return 0;
> + return rc;
> }
>
> int arch_monitor_domctl_event(struct domain *d,
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