[Qemu-devel] [PATCH v2 for-1.4] tests/test-string-input-visitor: Handle errors provoked by fuzz test

[Peter Maydell]

It's OK and expected for visitors to return errors when presented with
the fuzz test's random data. Since the fuzzer doesn't care about
errors, we pass in NULL rather than an Error**. This fixes a bug in
the fuzzer where it was passing the same Error** into each visitor,
with the effect that once one visitor returned an error, each later
visitor would notice that it had been passed in an Error** representing
an already set error, and do nothing.

For the case of visit_type_str() we also need to handle the case where
an error means that the visitor doesn't set our char*. We initialize
the pointer to NULL so we can safely g_free() it regardless of whether
the visitor allocated a string for us or not.

This fixes a problem where this test failed the MacOSX malloc()
consistency checks and might segfault on other platforms [due
to calling free() on an uninitialized pointer variable when
visit_type_str() failed.].

Signed-off-by: Peter Maydell <address@hidden>
---
For 1.4 because it fixes a crash bug in the test.

v1->v2 changes: I took Luiz' suggestions for simplifying this code:
just pass NULL in as an Error** since we don't care about errors, and
NULL-init sres so g_free() works either way.

I agree with Luiz that the test leaks visitors, but since it won't leak
enough to actually cause a problem, I leave that for a post-1.4 patch,
since it's a separate bug to the one we're fixing here.

 tests/test-string-input-visitor.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/tests/test-string-input-visitor.c 
b/tests/test-string-input-visitor.c
index f6b0093..5989f81 100644
--- a/tests/test-string-input-visitor.c
+++ b/tests/test-string-input-visitor.c
@@ -174,7 +174,6 @@ static void test_visitor_in_fuzz(TestInputVisitorData *data,
     double nres;
     char *sres;
     EnumOne eres;
-    Error *errp = NULL;
     Visitor *v;
     unsigned int i;
     char buf[10000];
@@ -193,21 +192,22 @@ static void test_visitor_in_fuzz(TestInputVisitorData 
*data,
         }
 
         v = visitor_input_test_init(data, buf);
-        visit_type_int(v, &ires, NULL, &errp);
+        visit_type_int(v, &ires, NULL, NULL);
 
         v = visitor_input_test_init(data, buf);
-        visit_type_bool(v, &bres, NULL, &errp);
+        visit_type_bool(v, &bres, NULL, NULL);
         visitor_input_teardown(data, NULL);
 
         v = visitor_input_test_init(data, buf);
-        visit_type_number(v, &nres, NULL, &errp);
+        visit_type_number(v, &nres, NULL, NULL);
 
         v = visitor_input_test_init(data, buf);
-        visit_type_str(v, &sres, NULL, &errp);
+        sres = NULL;
+        visit_type_str(v, &sres, NULL, NULL);
         g_free(sres);
 
         v = visitor_input_test_init(data, buf);
-        visit_type_EnumOne(v, &eres, NULL, &errp);
+        visit_type_EnumOne(v, &eres, NULL, NULL);
         visitor_input_teardown(data, NULL);
     }
 }
-- 
1.7.11.4