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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 3/8] x86/vm-event/monitor: don't compromise monitor_write_data on domain cleanup
The arch_vm_event structure is dynamically allocated and freed @
vm_event_cleanup_domain. This cleanup is triggered e.g. when the toolstack user
disables domain monitoring (xc_monitor_disable), which in turn effectively
discards any information that was in arch_vm_event.write_data.
But this can yield unexpected behavior since if a CR-write was awaiting to be
committed on the scheduling tail (hvm_do_resume->arch_monitor_write_data)
before xc_monitor_disable is called, then the domain CR write is wrongfully
ignored, which of course, in these cases, can easily render a domain crash.
To fix the issue, this patch:
- makes arch_vm_event.emul_read_data dynamically allocated
- in vm_event_cleanup_domain, if there are still uncommitted writes in
arch_vm_event.write_data:
- only frees emul_read_data
- defers xfree of the entire arch_vm_event until vcpu/domain destroyal
- otherwise arch_vm_event is freed in vm_event_cleanup_domain, as before
For clarity, also introduce inline functions that check initialisation of the
vm_event subsystem for a vcpu/domain (vm_event_{vcpu,domain}_initialised), since
that is now true only when both arch_vm_event and arch_vm_event.emul_read_data
are non-NULL.
Signed-off-by: Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>
---
Changed since v2:
* introduce vm_event_{vcpu,domain}_initialised inline functions for clarity
* xfree arch_vm_event in vm_event_cleanup_domain as before if there are no
uncommitted writes in arch_vm_event.write_data
---
xen/arch/x86/domain.c | 9 +++++++--
xen/arch/x86/hvm/emulate.c | 6 +++---
xen/arch/x86/hvm/hvm.c | 2 ++
xen/arch/x86/mm/p2m.c | 2 +-
xen/arch/x86/vm_event.c | 35 +++++++++++++++++++++++++++++------
xen/common/vm_event.c | 12 ++++++++++++
xen/include/asm-x86/domain.h | 17 +++++++++++------
xen/include/asm-x86/monitor.h | 3 ++-
xen/include/asm-x86/vm_event.h | 13 ++++++++++++-
9 files changed, 79 insertions(+), 20 deletions(-)
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index bb59247..0313208 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -56,6 +56,7 @@
#include <asm/debugreg.h>
#include <asm/msr.h>
#include <asm/traps.h>
+#include <asm/vm_event.h>
#include <asm/nmi.h>
#include <asm/mce.h>
#include <asm/amd.h>
@@ -492,8 +493,12 @@ int vcpu_initialise(struct vcpu *v)
void vcpu_destroy(struct vcpu *v)
{
- xfree(v->arch.vm_event);
- v->arch.vm_event = NULL;
+ if ( unlikely(v->arch.vm_event) )
+ {
+ xfree(v->arch.vm_event->emul_read_data);
+ xfree(v->arch.vm_event);
+ v->arch.vm_event = NULL;
+ }
if ( is_pv_32bit_vcpu(v) )
{
diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 855af4d..59e2344 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -73,12 +73,12 @@ static int set_context_data(void *buffer, unsigned int size)
{
struct vcpu *curr = current;
- if ( curr->arch.vm_event )
+ if ( vm_event_vcpu_initialised(curr) )
{
unsigned int safe_size =
- min(size, curr->arch.vm_event->emul_read_data.size);
+ min(size, curr->arch.vm_event->emul_read_data->size);
- memcpy(buffer, curr->arch.vm_event->emul_read_data.data, safe_size);
+ memcpy(buffer, curr->arch.vm_event->emul_read_data->data, safe_size);
memset(buffer + safe_size, 0, size - safe_size);
return X86EMUL_OKAY;
}
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index e3829d2..ac6d9eb 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -479,6 +479,8 @@ void hvm_do_resume(struct vcpu *v)
{
enum emul_kind kind = EMUL_KIND_NORMAL;
+ ASSERT(v->arch.vm_event->emul_read_data);
+
if ( v->arch.vm_event->emulate_flags &
VM_EVENT_FLAG_SET_EMUL_READ_DATA )
kind = EMUL_KIND_SET_CONTEXT;
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 16733a4..6616626 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -1642,7 +1642,7 @@ void p2m_mem_access_emulate_check(struct vcpu *v,
v->arch.vm_event->emulate_flags = violation ? rsp->flags : 0;
if ( (rsp->flags & VM_EVENT_FLAG_SET_EMUL_READ_DATA) )
- v->arch.vm_event->emul_read_data = rsp->data.emul_read_data;
+ *v->arch.vm_event->emul_read_data = rsp->data.emul_read_data;
}
}
diff --git a/xen/arch/x86/vm_event.c b/xen/arch/x86/vm_event.c
index 80f84d6..ff2ba92 100644
--- a/xen/arch/x86/vm_event.c
+++ b/xen/arch/x86/vm_event.c
@@ -30,12 +30,18 @@ int vm_event_init_domain(struct domain *d)
for_each_vcpu ( d, v )
{
- if ( v->arch.vm_event )
+ if ( likely(!v->arch.vm_event) )
+ {
+ v->arch.vm_event = xzalloc(struct arch_vm_event);
+ if ( !v->arch.vm_event )
+ return -ENOMEM;
+ }
+ else if ( unlikely(v->arch.vm_event->emul_read_data) )
continue;
- v->arch.vm_event = xzalloc(struct arch_vm_event);
-
- if ( !v->arch.vm_event )
+ v->arch.vm_event->emul_read_data =
+ xzalloc(struct vm_event_emul_read_data);
+ if ( !v->arch.vm_event->emul_read_data )
return -ENOMEM;
}
@@ -52,8 +58,25 @@ void vm_event_cleanup_domain(struct domain *d)
for_each_vcpu ( d, v )
{
- xfree(v->arch.vm_event);
- v->arch.vm_event = NULL;
+ if ( likely(!v->arch.vm_event) )
+ continue;
+
+ /*
+ * Only xfree the entire arch_vm_event if write_data was fully handled.
+ * Otherwise defer entire xfree until domain/vcpu destroyal.
+ */
+ if ( likely(!v->arch.vm_event->write_data.uncommitted_writes) )
+ {
+ xfree(v->arch.vm_event->emul_read_data);
+ xfree(v->arch.vm_event);
+ v->arch.vm_event = NULL;
+ continue;
+ }
+
+ /* write_data not fully handled, only xfree emul_read_data */
+ v->arch.vm_event->emulate_flags = 0;
+ xfree(v->arch.vm_event->emul_read_data);
+ v->arch.vm_event->emul_read_data = NULL;
}
d->arch.mem_access_emulate_each_rep = 0;
diff --git a/xen/common/vm_event.c b/xen/common/vm_event.c
index 17d2716..47ae96c 100644
--- a/xen/common/vm_event.c
+++ b/xen/common/vm_event.c
@@ -534,6 +534,8 @@ static void mem_sharing_notification(struct vcpu *v,
unsigned int port)
/* Clean up on domain destruction */
void vm_event_cleanup(struct domain *d)
{
+ struct vcpu *v;
+
#ifdef CONFIG_HAS_MEM_PAGING
if ( d->vm_event->paging.ring_page )
{
@@ -560,6 +562,16 @@ void vm_event_cleanup(struct domain *d)
(void)vm_event_disable(d, &d->vm_event->share);
}
#endif
+
+ for_each_vcpu ( d, v )
+ {
+ if ( unlikely(v->arch.vm_event) )
+ {
+ /* vm_event->emul_read_data freed in vm_event_cleanup_domain */
+ xfree(v->arch.vm_event);
+ v->arch.vm_event = NULL;
+ }
+ }
}
int vm_event_domctl(struct domain *d, xen_domctl_vm_event_op_t *vec,
diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index 8f64ae9..0e3e139 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -260,12 +260,17 @@ struct pv_domain
};
struct monitor_write_data {
- struct {
- unsigned int msr : 1;
- unsigned int cr0 : 1;
- unsigned int cr3 : 1;
- unsigned int cr4 : 1;
- } do_write;
+ union {
+ struct {
+ unsigned int msr : 1;
+ unsigned int cr0 : 1;
+ unsigned int cr3 : 1;
+ unsigned int cr4 : 1;
+ } do_write;
+
+ /* non-zero when at least one of do_write fields is non-zero */
+ unsigned int uncommitted_writes;
+ };
uint32_t msr;
uint64_t value;
diff --git a/xen/include/asm-x86/monitor.h b/xen/include/asm-x86/monitor.h
index 0611681..9238ec8 100644
--- a/xen/include/asm-x86/monitor.h
+++ b/xen/include/asm-x86/monitor.h
@@ -26,6 +26,7 @@
#include <public/domctl.h>
#include <asm/cpufeature.h>
#include <asm/hvm/hvm.h>
+#include <asm/vm_event.h>
#define monitor_ctrlreg_bitmask(ctrlreg_index) (1U << (ctrlreg_index))
@@ -48,7 +49,7 @@ int arch_monitor_domctl_op(struct domain *d, struct
xen_domctl_monitor_op *mop)
* Enabling mem_access_emulate_each_rep without a vm_event subscriber
* is meaningless.
*/
- if ( d->max_vcpus && d->vcpu[0] && d->vcpu[0]->arch.vm_event )
+ if ( vm_event_domain_initialised(d) )
d->arch.mem_access_emulate_each_rep = !!mop->event;
else
rc = -EINVAL;
diff --git a/xen/include/asm-x86/vm_event.h b/xen/include/asm-x86/vm_event.h
index 026f42e..9bdeccc 100644
--- a/xen/include/asm-x86/vm_event.h
+++ b/xen/include/asm-x86/vm_event.h
@@ -28,12 +28,23 @@
*/
struct arch_vm_event {
uint32_t emulate_flags;
- struct vm_event_emul_read_data emul_read_data;
+ struct vm_event_emul_read_data *emul_read_data;
struct monitor_write_data write_data;
};
int vm_event_init_domain(struct domain *d);
+static inline bool_t vm_event_vcpu_initialised(struct vcpu *v)
+{
+ return (v->arch.vm_event && v->arch.vm_event->emul_read_data);
+}
+
+static inline bool_t vm_event_domain_initialised(struct domain *d)
+{
+ return (d->max_vcpus && d->vcpu[0] &&
+ vm_event_vcpu_initialised(d->vcpu[0]));
+}
+
void vm_event_cleanup_domain(struct domain *d);
void vm_event_toggle_singlestep(struct domain *d, struct vcpu *v);
--
2.5.0
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