[Qemu-devel] [PATCH v3] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

[Qemu-devel] [PATCH v3] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

[Ashijeet Acharya]

Commit a3a3d8c7 introduced a segfault bug while checking for
'dc->vmsd->unmigratable' which caused QEMU to crash when trying to add
devices which do no set their 'dc->vmsd' yet while initialization.
Place a 'dc->vmsd' check prior to it so that we do not segfault for
such devices.

NOTE: This doesn't compromise the functioning of --only-migratable
option as all the unmigratable devices do set their 'dc->vmsd'.

Also, move the only_migratable check inside device_set_realized() to avoid
code duplication and fix the bug to display only_migratable error message
only if the device constructuon is right.

Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
---
Changes is v3:
- move only_migratable check inside device_set_realized() to avoid code 
- duplication
- I have dropped Juan's R-b tag for this one
Changes in v2:
- place dc->vmsd check in hw/usb/bus.c as well
---
 hw/core/qdev.c | 10 ++++++++++
 hw/usb/bus.c   | 19 -------------------
 qdev-monitor.c |  9 ---------
 3 files changed, 10 insertions(+), 28 deletions(-)

diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index 5783442..4438cbf 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -37,6 +37,7 @@
 #include "hw/boards.h"
 #include "hw/sysbus.h"
 #include "qapi-event.h"
+#include "migration/migration.h"
 
 int qdev_hotplug = 0;
 static bool qdev_hot_added = false;
@@ -896,6 +897,15 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
     }
 
     if (value && !dev->realized) {
+        if (only_migratable && dc->vmsd) {
+            if (dc->vmsd->unmigratable) {
+                error_setg(&local_err, "Device %s is not migratable, but "
+                           "--only-migratable was specified",
+                           object_get_typename(obj));
+                goto fail;
+            }
+        }
+
         if (!obj->parent) {
             gchar *name = g_strdup_printf("device[%d]", unattached_count++);
 
diff --git a/hw/usb/bus.c b/hw/usb/bus.c
index 1dcc35c..25913ad 100644
--- a/hw/usb/bus.c
+++ b/hw/usb/bus.c
@@ -8,7 +8,6 @@
 #include "monitor/monitor.h"
 #include "trace.h"
 #include "qemu/cutils.h"
-#include "migration/migration.h"
 
 static void usb_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent);
 
@@ -687,8 +686,6 @@ USBDevice *usbdevice_create(const char *cmdline)
     const char *params;
     int len;
     USBDevice *dev;
-    ObjectClass *klass;
-    DeviceClass *dc;
 
     params = strchr(cmdline,':');
     if (params) {
@@ -723,22 +720,6 @@ USBDevice *usbdevice_create(const char *cmdline)
         return NULL;
     }
 
-    klass = object_class_by_name(f->name);
-    if (klass == NULL) {
-        error_report("Device '%s' not found", f->name);
-        return NULL;
-    }
-
-    dc = DEVICE_CLASS(klass);
-
-    if (only_migratable) {
-        if (dc->vmsd->unmigratable) {
-            error_report("Device %s is not migratable, but --only-migratable "
-                         "was specified", f->name);
-            return NULL;
-        }
-    }
-
     if (f->usbdevice_init) {
         dev = f->usbdevice_init(bus, params);
     } else {
diff --git a/qdev-monitor.c b/qdev-monitor.c
index 549f45f..5f2fcdf 100644
--- a/qdev-monitor.c
+++ b/qdev-monitor.c
@@ -29,7 +29,6 @@
 #include "qemu/error-report.h"
 #include "qemu/help_option.h"
 #include "sysemu/block-backend.h"
-#include "migration/migration.h"
 
 /*
  * Aliases were a bad idea from the start.  Let's keep them
@@ -579,14 +578,6 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
         return NULL;
     }
 
-    if (only_migratable) {
-        if (dc->vmsd->unmigratable) {
-            error_setg(errp, "Device %s is not migratable, but "
-                       "--only-migratable was specified", driver);
-            return NULL;
-        }
-    }
-
     /* find bus */
     path = qemu_opt_get(opts, "bus");
     if (path != NULL) {
-- 
2.6.2

Re: [Qemu-devel] [PATCH v3] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

[Paolo Bonzini]

On 04/02/2017 04:21, Ashijeet Acharya wrote:
> Commit a3a3d8c7 introduced a segfault bug while checking for
> 'dc->vmsd->unmigratable' which caused QEMU to crash when trying to add
> devices which do no set their 'dc->vmsd' yet while initialization.
> Place a 'dc->vmsd' check prior to it so that we do not segfault for
> such devices.
> 
> NOTE: This doesn't compromise the functioning of --only-migratable
> option as all the unmigratable devices do set their 'dc->vmsd'.
> 
> Also, move the only_migratable check inside device_set_realized() to avoid
> code duplication and fix the bug to display only_migratable error message
> only if the device constructuon is right.
> 
> Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
> ---
> Changes is v3:
> - move only_migratable check inside device_set_realized() to avoid code 
> - duplication
> - I have dropped Juan's R-b tag for this one
> Changes in v2:
> - place dc->vmsd check in hw/usb/bus.c as well
> ---
>  hw/core/qdev.c | 10 ++++++++++
>  hw/usb/bus.c   | 19 -------------------
>  qdev-monitor.c |  9 ---------
>  3 files changed, 10 insertions(+), 28 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 5783442..4438cbf 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -37,6 +37,7 @@
>  #include "hw/boards.h"
>  #include "hw/sysbus.h"
>  #include "qapi-event.h"
> +#include "migration/migration.h"
>  
>  int qdev_hotplug = 0;
>  static bool qdev_hot_added = false;
> @@ -896,6 +897,15 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
>      }
>  
>      if (value && !dev->realized) {
> +        if (only_migratable && dc->vmsd) {
> +            if (dc->vmsd->unmigratable) {
> +                error_setg(&local_err, "Device %s is not migratable, but "
> +                           "--only-migratable was specified",
> +                           object_get_typename(obj));
> +                goto fail;
> +            }
> +        }
> +
>          if (!obj->parent) {
>              gchar *name = g_strdup_printf("device[%d]", unattached_count++);
>  
> diff --git a/hw/usb/bus.c b/hw/usb/bus.c
> index 1dcc35c..25913ad 100644
> --- a/hw/usb/bus.c
> +++ b/hw/usb/bus.c
> @@ -8,7 +8,6 @@
>  #include "monitor/monitor.h"
>  #include "trace.h"
>  #include "qemu/cutils.h"
> -#include "migration/migration.h"
>  
>  static void usb_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent);
>  
> @@ -687,8 +686,6 @@ USBDevice *usbdevice_create(const char *cmdline)
>      const char *params;
>      int len;
>      USBDevice *dev;
> -    ObjectClass *klass;
> -    DeviceClass *dc;
>  
>      params = strchr(cmdline,':');
>      if (params) {
> @@ -723,22 +720,6 @@ USBDevice *usbdevice_create(const char *cmdline)
>          return NULL;
>      }
>  
> -    klass = object_class_by_name(f->name);
> -    if (klass == NULL) {
> -        error_report("Device '%s' not found", f->name);
> -        return NULL;
> -    }
> -
> -    dc = DEVICE_CLASS(klass);
> -
> -    if (only_migratable) {
> -        if (dc->vmsd->unmigratable) {
> -            error_report("Device %s is not migratable, but --only-migratable "
> -                         "was specified", f->name);
> -            return NULL;
> -        }
> -    }
> -
>      if (f->usbdevice_init) {
>          dev = f->usbdevice_init(bus, params);
>      } else {
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index 549f45f..5f2fcdf 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -29,7 +29,6 @@
>  #include "qemu/error-report.h"
>  #include "qemu/help_option.h"
>  #include "sysemu/block-backend.h"
> -#include "migration/migration.h"
>  
>  /*
>   * Aliases were a bad idea from the start.  Let's keep them
> @@ -579,14 +578,6 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
>          return NULL;
>      }
>  
> -    if (only_migratable) {
> -        if (dc->vmsd->unmigratable) {
> -            error_setg(errp, "Device %s is not migratable, but "
> -                       "--only-migratable was specified", driver);
> -            return NULL;
> -        }
> -    }
> -
>      /* find bus */
>      path = qemu_opt_get(opts, "bus");
>      if (path != NULL) {
> 

Reviewed-bv: Paolo Bonzini <pbonzinI@redhat.com>

Re: [Qemu-devel] [PATCH v3] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

[Dr. David Alan Gilbert]

* Ashijeet Acharya (ashijeetacharya@gmail.com) wrote:
> Commit a3a3d8c7 introduced a segfault bug while checking for
> 'dc->vmsd->unmigratable' which caused QEMU to crash when trying to add
> devices which do no set their 'dc->vmsd' yet while initialization.
> Place a 'dc->vmsd' check prior to it so that we do not segfault for
> such devices.
> 
> NOTE: This doesn't compromise the functioning of --only-migratable
> option as all the unmigratable devices do set their 'dc->vmsd'.
> 
> Also, move the only_migratable check inside device_set_realized() to avoid
> code duplication and fix the bug to display only_migratable error message
> only if the device constructuon is right.
> 
> Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>

Queued

> ---
> Changes is v3:
> - move only_migratable check inside device_set_realized() to avoid code 
> - duplication
> - I have dropped Juan's R-b tag for this one
> Changes in v2:
> - place dc->vmsd check in hw/usb/bus.c as well
> ---
>  hw/core/qdev.c | 10 ++++++++++
>  hw/usb/bus.c   | 19 -------------------
>  qdev-monitor.c |  9 ---------
>  3 files changed, 10 insertions(+), 28 deletions(-)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 5783442..4438cbf 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -37,6 +37,7 @@
>  #include "hw/boards.h"
>  #include "hw/sysbus.h"
>  #include "qapi-event.h"
> +#include "migration/migration.h"
>  
>  int qdev_hotplug = 0;
>  static bool qdev_hot_added = false;
> @@ -896,6 +897,15 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
>      }
>  
>      if (value && !dev->realized) {
> +        if (only_migratable && dc->vmsd) {
> +            if (dc->vmsd->unmigratable) {
> +                error_setg(&local_err, "Device %s is not migratable, but "
> +                           "--only-migratable was specified",
> +                           object_get_typename(obj));
> +                goto fail;
> +            }
> +        }
> +
>          if (!obj->parent) {
>              gchar *name = g_strdup_printf("device[%d]", unattached_count++);
>  
> diff --git a/hw/usb/bus.c b/hw/usb/bus.c
> index 1dcc35c..25913ad 100644
> --- a/hw/usb/bus.c
> +++ b/hw/usb/bus.c
> @@ -8,7 +8,6 @@
>  #include "monitor/monitor.h"
>  #include "trace.h"
>  #include "qemu/cutils.h"
> -#include "migration/migration.h"
>  
>  static void usb_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent);
>  
> @@ -687,8 +686,6 @@ USBDevice *usbdevice_create(const char *cmdline)
>      const char *params;
>      int len;
>      USBDevice *dev;
> -    ObjectClass *klass;
> -    DeviceClass *dc;
>  
>      params = strchr(cmdline,':');
>      if (params) {
> @@ -723,22 +720,6 @@ USBDevice *usbdevice_create(const char *cmdline)
>          return NULL;
>      }
>  
> -    klass = object_class_by_name(f->name);
> -    if (klass == NULL) {
> -        error_report("Device '%s' not found", f->name);
> -        return NULL;
> -    }
> -
> -    dc = DEVICE_CLASS(klass);
> -
> -    if (only_migratable) {
> -        if (dc->vmsd->unmigratable) {
> -            error_report("Device %s is not migratable, but --only-migratable "
> -                         "was specified", f->name);
> -            return NULL;
> -        }
> -    }
> -
>      if (f->usbdevice_init) {
>          dev = f->usbdevice_init(bus, params);
>      } else {
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index 549f45f..5f2fcdf 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -29,7 +29,6 @@
>  #include "qemu/error-report.h"
>  #include "qemu/help_option.h"
>  #include "sysemu/block-backend.h"
> -#include "migration/migration.h"
>  
>  /*
>   * Aliases were a bad idea from the start.  Let's keep them
> @@ -579,14 +578,6 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
>          return NULL;
>      }
>  
> -    if (only_migratable) {
> -        if (dc->vmsd->unmigratable) {
> -            error_setg(errp, "Device %s is not migratable, but "
> -                       "--only-migratable was specified", driver);
> -            return NULL;
> -        }
> -    }
> -
>      /* find bus */
>      path = qemu_opt_get(opts, "bus");
>      if (path != NULL) {
> -- 
> 2.6.2
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH v3] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

[Dr. David Alan Gilbert]

* Dr. David Alan Gilbert (dgilbert@redhat.com) wrote:
> * Ashijeet Acharya (ashijeetacharya@gmail.com) wrote:
> > Commit a3a3d8c7 introduced a segfault bug while checking for
> > 'dc->vmsd->unmigratable' which caused QEMU to crash when trying to add
> > devices which do no set their 'dc->vmsd' yet while initialization.
> > Place a 'dc->vmsd' check prior to it so that we do not segfault for
> > such devices.
> > 
> > NOTE: This doesn't compromise the functioning of --only-migratable
> > option as all the unmigratable devices do set their 'dc->vmsd'.
> > 
> > Also, move the only_migratable check inside device_set_realized() to avoid
> > code duplication and fix the bug to display only_migratable error message
> > only if the device constructuon is right.
> > 
> > Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
> 
> Queued

I've had to remove this;  it fails to build user-mode qemu's.
I think the problem is only_migratable is in vl.c and doesn't
get linked in user mode qemu; I tried adding a #ifndef CONFIG_USER_ONLY
around the block and it didn't help, so back to you.

Dave

> > ---
> > Changes is v3:
> > - move only_migratable check inside device_set_realized() to avoid code 
> > - duplication
> > - I have dropped Juan's R-b tag for this one
> > Changes in v2:
> > - place dc->vmsd check in hw/usb/bus.c as well
> > ---
> >  hw/core/qdev.c | 10 ++++++++++
> >  hw/usb/bus.c   | 19 -------------------
> >  qdev-monitor.c |  9 ---------
> >  3 files changed, 10 insertions(+), 28 deletions(-)
> > 
> > diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> > index 5783442..4438cbf 100644
> > --- a/hw/core/qdev.c
> > +++ b/hw/core/qdev.c
> > @@ -37,6 +37,7 @@
> >  #include "hw/boards.h"
> >  #include "hw/sysbus.h"
> >  #include "qapi-event.h"
> > +#include "migration/migration.h"
> >  
> >  int qdev_hotplug = 0;
> >  static bool qdev_hot_added = false;
> > @@ -896,6 +897,15 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
> >      }
> >  
> >      if (value && !dev->realized) {
> > +        if (only_migratable && dc->vmsd) {
> > +            if (dc->vmsd->unmigratable) {
> > +                error_setg(&local_err, "Device %s is not migratable, but "
> > +                           "--only-migratable was specified",
> > +                           object_get_typename(obj));
> > +                goto fail;
> > +            }
> > +        }
> > +
> >          if (!obj->parent) {
> >              gchar *name = g_strdup_printf("device[%d]", unattached_count++);
> >  
> > diff --git a/hw/usb/bus.c b/hw/usb/bus.c
> > index 1dcc35c..25913ad 100644
> > --- a/hw/usb/bus.c
> > +++ b/hw/usb/bus.c
> > @@ -8,7 +8,6 @@
> >  #include "monitor/monitor.h"
> >  #include "trace.h"
> >  #include "qemu/cutils.h"
> > -#include "migration/migration.h"
> >  
> >  static void usb_bus_dev_print(Monitor *mon, DeviceState *qdev, int indent);
> >  
> > @@ -687,8 +686,6 @@ USBDevice *usbdevice_create(const char *cmdline)
> >      const char *params;
> >      int len;
> >      USBDevice *dev;
> > -    ObjectClass *klass;
> > -    DeviceClass *dc;
> >  
> >      params = strchr(cmdline,':');
> >      if (params) {
> > @@ -723,22 +720,6 @@ USBDevice *usbdevice_create(const char *cmdline)
> >          return NULL;
> >      }
> >  
> > -    klass = object_class_by_name(f->name);
> > -    if (klass == NULL) {
> > -        error_report("Device '%s' not found", f->name);
> > -        return NULL;
> > -    }
> > -
> > -    dc = DEVICE_CLASS(klass);
> > -
> > -    if (only_migratable) {
> > -        if (dc->vmsd->unmigratable) {
> > -            error_report("Device %s is not migratable, but --only-migratable "
> > -                         "was specified", f->name);
> > -            return NULL;
> > -        }
> > -    }
> > -
> >      if (f->usbdevice_init) {
> >          dev = f->usbdevice_init(bus, params);
> >      } else {
> > diff --git a/qdev-monitor.c b/qdev-monitor.c
> > index 549f45f..5f2fcdf 100644
> > --- a/qdev-monitor.c
> > +++ b/qdev-monitor.c
> > @@ -29,7 +29,6 @@
> >  #include "qemu/error-report.h"
> >  #include "qemu/help_option.h"
> >  #include "sysemu/block-backend.h"
> > -#include "migration/migration.h"
> >  
> >  /*
> >   * Aliases were a bad idea from the start.  Let's keep them
> > @@ -579,14 +578,6 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
> >          return NULL;
> >      }
> >  
> > -    if (only_migratable) {
> > -        if (dc->vmsd->unmigratable) {
> > -            error_setg(errp, "Device %s is not migratable, but "
> > -                       "--only-migratable was specified", driver);
> > -            return NULL;
> > -        }
> > -    }
> > -
> >      /* find bus */
> >      path = qemu_opt_get(opts, "bus");
> >      if (path != NULL) {
> > -- 
> > 2.6.2
> > 
> > 
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] [PATCH v3] migrate: Introduce a 'dc->vmsd' check to avoid segfault for --only-migratable

[Paolo Bonzini]

On 13/02/2017 16:14, Dr. David Alan Gilbert wrote:
> * Dr. David Alan Gilbert (dgilbert@redhat.com) wrote:
>> * Ashijeet Acharya (ashijeetacharya@gmail.com) wrote:
>>> Commit a3a3d8c7 introduced a segfault bug while checking for
>>> 'dc->vmsd->unmigratable' which caused QEMU to crash when trying to add
>>> devices which do no set their 'dc->vmsd' yet while initialization.
>>> Place a 'dc->vmsd' check prior to it so that we do not segfault for
>>> such devices.
>>>
>>> NOTE: This doesn't compromise the functioning of --only-migratable
>>> option as all the unmigratable devices do set their 'dc->vmsd'.
>>>
>>> Also, move the only_migratable check inside device_set_realized() to avoid
>>> code duplication and fix the bug to display only_migratable error message
>>> only if the device constructuon is right.
>>>
>>> Signed-off-by: Ashijeet Acharya <ashijeetacharya@gmail.com>
>>
>> Queued
> 
> I've had to remove this;  it fails to build user-mode qemu's.
> I think the problem is only_migratable is in vl.c and doesn't
> get linked in user mode qemu; I tried adding a #ifndef CONFIG_USER_ONLY
> around the block and it didn't help, so back to you.\

It doesn't help because the file is compiled just once.  You can add it
to stubs/ (for example stubs/vmstate.c).

Paolo