[Qemu-devel] [PATCH v2 0/2] qom: Fix misuse of Error API

[Qemu-devel] [PATCH v2 0/2] qom: Fix misuse of Error API

[Markus Armbruster]

v1 was posted for possible inclusion into 2.4, but the maintainer
didn't bite ;-)

v2:
* Commit messages updated.

Markus Armbruster (2):
  qom: Do not reuse errp after a possible error
  qom: Fix invalid error check in property_get_str()

 qom/object.c | 53 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 43 insertions(+), 10 deletions(-)

-- 
2.4.3

[Qemu-devel] [PATCH v2 1/2] qom: Do not reuse errp after a possible error

[Markus Armbruster]

The argument for an Error **errp parameter must point to a null
pointer.  If it doesn't, and an error happens, error_set() fails its
assertion.

Instead of

    foo(foos, errp);
    bar(bars, errp);

you need to do something like

    Error *err = NULL;

    foo(foos, &err);
    if (err) {
        error_propagate(errp, err);
        goto out;
    }

    bar(bars, errp);
out:

Screwed up in commit 0e55884 (v1.3.0): property_get_bool().

Screwed up in commit 1f21772 (v2.1.0): object_property_get_enum() and
object_property_get_uint16List().

Screwed up in commit a8e3fbe (v2.4.0): property_get_enum(),
property_set_enum().

Found by inspection, no actual crashes observed.

Fix them up.

Cc: Andreas Färber <afaerber@suse.de>
Cc: Anthony Liguori <anthony@codemonkey.ws>
Cc: Hu Tao <hutao@cn.fujitsu.com>
Cc: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
---
 qom/object.c | 41 +++++++++++++++++++++++++++++++++++------
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/qom/object.c b/qom/object.c
index eea8edf..6173da8 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1079,6 +1079,7 @@ typedef struct EnumProperty {
 int object_property_get_enum(Object *obj, const char *name,
                              const char *typename, Error **errp)
 {
+    Error *err = NULL;
     StringOutputVisitor *sov;
     StringInputVisitor *siv;
     char *str;
@@ -1100,7 +1101,12 @@ int object_property_get_enum(Object *obj, const char *name,
     enumprop = prop->opaque;
 
     sov = string_output_visitor_new(false);
-    object_property_get(obj, string_output_get_visitor(sov), name, errp);
+    object_property_get(obj, string_output_get_visitor(sov), name, &err);
+    if (err) {
+        error_propagate(errp, err);
+        string_output_visitor_cleanup(sov);
+        return 0;
+    }
     str = string_output_get_string(sov);
     siv = string_input_visitor_new(str);
     string_output_visitor_cleanup(sov);
@@ -1116,21 +1122,27 @@ int object_property_get_enum(Object *obj, const char *name,
 void object_property_get_uint16List(Object *obj, const char *name,
                                     uint16List **list, Error **errp)
 {
+    Error *err = NULL;
     StringOutputVisitor *ov;
     StringInputVisitor *iv;
     char *str;
 
     ov = string_output_visitor_new(false);
     object_property_get(obj, string_output_get_visitor(ov),
-                        name, errp);
+                        name, &err);
+    if (err) {
+        error_propagate(errp, err);
+        goto out;
+    }
     str = string_output_get_string(ov);
     iv = string_input_visitor_new(str);
     visit_type_uint16List(string_input_get_visitor(iv),
                           list, NULL, errp);
 
     g_free(str);
-    string_output_visitor_cleanup(ov);
     string_input_visitor_cleanup(iv);
+out:
+    string_output_visitor_cleanup(ov);
 }
 
 void object_property_parse(Object *obj, const char *string,
@@ -1644,10 +1656,16 @@ typedef struct BoolProperty
 static void property_get_bool(Object *obj, Visitor *v, void *opaque,
                               const char *name, Error **errp)
 {
+    Error *err = NULL;
     BoolProperty *prop = opaque;
     bool value;
 
-    value = prop->get(obj, errp);
+    value = prop->get(obj, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    }
+
     visit_type_bool(v, &value, name, errp);
 }
 
@@ -1699,20 +1717,31 @@ void object_property_add_bool(Object *obj, const char *name,
 static void property_get_enum(Object *obj, Visitor *v, void *opaque,
                               const char *name, Error **errp)
 {
+    Error *err = NULL;
     EnumProperty *prop = opaque;
     int value;
 
-    value = prop->get(obj, errp);
+    value = prop->get(obj, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    }
+
     visit_type_enum(v, &value, prop->strings, NULL, name, errp);
 }
 
 static void property_set_enum(Object *obj, Visitor *v, void *opaque,
                               const char *name, Error **errp)
 {
+    Error *err = NULL;
     EnumProperty *prop = opaque;
     int value;
 
-    visit_type_enum(v, &value, prop->strings, NULL, name, errp);
+    visit_type_enum(v, &value, prop->strings, NULL, name, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
+    }
     prop->set(obj, value, errp);
 }
 
-- 
2.4.3

[Qemu-devel] [PATCH v2 2/2] qom: Fix invalid error check in property_get_str()

[Markus Armbruster]

When a function returns a null pointer on error and only on error, you
can do

    if (!foo(foos, errp)) {
        ... handle error ...
    }

instead of the more cumbersome

    Error *err = NULL;

    if (!foo(foos, &err)) {
        error_propagate(errp, err);
        ... handle error ...
    }

A StringProperty's getter, however, may return null on success!  We
then fail to call visit_type_str().

Screwed up in 6a146eb, v1.1.

Fails tests/qom-test in my current, heavily hacked QAPI branch.  No
reproducer for master known (but I didn't look hard).

Cc: Andreas Färber <afaerber@suse.de>
Cc: Anthony Liguori <anthony@codemonkey.ws>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 qom/object.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/qom/object.c b/qom/object.c
index 6173da8..4c4df55 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1591,14 +1591,18 @@ typedef struct StringProperty
 static void property_get_str(Object *obj, Visitor *v, void *opaque,
                              const char *name, Error **errp)
 {
+    Error *err = NULL;
     StringProperty *prop = opaque;
     char *value;
 
-    value = prop->get(obj, errp);
-    if (value) {
-        visit_type_str(v, &value, name, errp);
-        g_free(value);
+    value = prop->get(obj, &err);
+    if (err) {
+        error_propagate(errp, err);
+        return;
     }
+
+    visit_type_str(v, &value, name, errp);
+    g_free(value);
 }
 
 static void property_set_str(Object *obj, Visitor *v, void *opaque,
-- 
2.4.3

Re: [Qemu-devel] [PATCH v2 0/2] qom: Fix misuse of Error API

[Markus Armbruster]

Ping?

My "qapi: QMP introspection" series fails "make check" without these
fixes.

Markus Armbruster <armbru@redhat.com> writes:

> v1 was posted for possible inclusion into 2.4, but the maintainer
> didn't bite ;-)
>
> v2:
> * Commit messages updated.
>
> Markus Armbruster (2):
>   qom: Do not reuse errp after a possible error
>   qom: Fix invalid error check in property_get_str()
>
>  qom/object.c | 53 +++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 43 insertions(+), 10 deletions(-)

Re: [Qemu-devel] [PATCH v2 0/2] qom: Fix misuse of Error API

[Eric Blake]

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On 09/03/2015 04:06 AM, Markus Armbruster wrote:
> Ping?
> 
> My "qapi: QMP introspection" series fails "make check" without these
> fixes.
> 
> Markus Armbruster <armbru@redhat.com> writes:
> 
>> v1 was posted for possible inclusion into 2.4, but the maintainer
>> didn't bite ;-)
>>
>> v2:
>> * Commit messages updated.
>>
>> Markus Armbruster (2):
>>   qom: Do not reuse errp after a possible error
>>   qom: Fix invalid error check in property_get_str()

Were you waiting for further review, or for the maintainer to speak up?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH v2 0/2] qom: Fix misuse of Error API

[Markus Armbruster]

Eric Blake <eblake@redhat.com> writes:

> On 09/03/2015 04:06 AM, Markus Armbruster wrote:
>> Ping?
>> 
>> My "qapi: QMP introspection" series fails "make check" without these
>> fixes.
>> 
>> Markus Armbruster <armbru@redhat.com> writes:
>> 
>>> v1 was posted for possible inclusion into 2.4, but the maintainer
>>> didn't bite ;-)
>>>
>>> v2:
>>> * Commit messages updated.
>>>
>>> Markus Armbruster (2):
>>>   qom: Do not reuse errp after a possible error
>>>   qom: Fix invalid error check in property_get_str()
>
> Were you waiting for further review, or for the maintainer to speak up?

The latter.  Andreas spoke up on IRC, and I hope he can get to this
small series in the next few days.

Re: [Qemu-devel] [PATCH v2 0/2] qom: Fix misuse of Error API

[Andreas Färber]

Am 03.09.2015 um 18:15 schrieb Markus Armbruster:
> Eric Blake <eblake@redhat.com> writes:
>> On 09/03/2015 04:06 AM, Markus Armbruster wrote:
>>> Ping?
>>>
>>> My "qapi: QMP introspection" series fails "make check" without these
>>> fixes.
>>>
>>> Markus Armbruster <armbru@redhat.com> writes:
>>>
>>>> v1 was posted for possible inclusion into 2.4, but the maintainer
>>>> didn't bite ;-)
>>>>
>>>> v2:
>>>> * Commit messages updated.
>>>>
>>>> Markus Armbruster (2):
>>>>   qom: Do not reuse errp after a possible error
>>>>   qom: Fix invalid error check in property_get_str()
>>
>> Were you waiting for further review, or for the maintainer to speak up?
> 
> The latter.  Andreas spoke up on IRC, and I hope he can get to this
> small series in the next few days.

Applied to qom-next, with stylistic changes to keep opaque variables first.
https://github.com/afaerber/qemu-cpu/commits/qom-next

Thanks,
Andreas

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