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

[Qemu-devel] [PATCH 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. This means the test harness needs to
handle them; check for and free any error after each visitor call,
and only free the string returned by visit_type_str if visit_type_str
succeeded.

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].

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 tests/test-string-input-visitor.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/tests/test-string-input-visitor.c b/tests/test-string-input-visitor.c
index f6b0093..793b334 100644
--- a/tests/test-string-input-visitor.c
+++ b/tests/test-string-input-visitor.c
@@ -194,20 +194,41 @@ static void test_visitor_in_fuzz(TestInputVisitorData *data,
 
         v = visitor_input_test_init(data, buf);
         visit_type_int(v, &ires, NULL, &errp);
+        if (error_is_set(&errp)) {
+            error_free(errp);
+            errp = NULL;
+        }
 
         v = visitor_input_test_init(data, buf);
         visit_type_bool(v, &bres, NULL, &errp);
+        if (error_is_set(&errp)) {
+            error_free(errp);
+            errp = NULL;
+        }
         visitor_input_teardown(data, NULL);
 
         v = visitor_input_test_init(data, buf);
         visit_type_number(v, &nres, NULL, &errp);
+        if (error_is_set(&errp)) {
+            error_free(errp);
+            errp = NULL;
+        }
 
         v = visitor_input_test_init(data, buf);
         visit_type_str(v, &sres, NULL, &errp);
-        g_free(sres);
+        if (error_is_set(&errp)) {
+            error_free(errp);
+            errp = NULL;
+        } else {
+            g_free(sres);
+        }
 
         v = visitor_input_test_init(data, buf);
         visit_type_EnumOne(v, &eres, NULL, &errp);
+        if (error_is_set(&errp)) {
+            error_free(errp);
+            errp = NULL;
+        }
         visitor_input_teardown(data, NULL);
     }
 }
-- 
1.7.11.4

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

[Andreas Färber]

Am 02.02.2013 22:19, schrieb Peter Maydell:
> It's OK and expected for visitors to return errors when presented with
> the fuzz test's random data. This means the test harness needs to
> handle them; check for and free any error after each visitor call,
> and only free the string returned by visit_type_str if visit_type_str
> succeeded.
> 
> 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].
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  tests/test-string-input-visitor.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/tests/test-string-input-visitor.c b/tests/test-string-input-visitor.c
> index f6b0093..793b334 100644
> --- a/tests/test-string-input-visitor.c
> +++ b/tests/test-string-input-visitor.c
> @@ -194,20 +194,41 @@ static void test_visitor_in_fuzz(TestInputVisitorData *data,
>  
>          v = visitor_input_test_init(data, buf);
>          visit_type_int(v, &ires, NULL, &errp);
> +        if (error_is_set(&errp)) {
> +            error_free(errp);
> +            errp = NULL;
> +        }

It seems to me the naming is bad here: errp appears to be an Error*, not
an Error**. It would be nice to fix this within the function touched.

Since it is an Error*, I think it was said that we should not use
error_is_set() but err != NULL (or if you prefer, just err).
error_is_set() is intended for **errp arguments that may be NULL.

Your analysis and the freeing and NULL'ing as solution looks correct.

Andreas

>  
>          v = visitor_input_test_init(data, buf);
>          visit_type_bool(v, &bres, NULL, &errp);
> +        if (error_is_set(&errp)) {
> +            error_free(errp);
> +            errp = NULL;
> +        }
>          visitor_input_teardown(data, NULL);
>  
>          v = visitor_input_test_init(data, buf);
>          visit_type_number(v, &nres, NULL, &errp);
> +        if (error_is_set(&errp)) {
> +            error_free(errp);
> +            errp = NULL;
> +        }
>  
>          v = visitor_input_test_init(data, buf);
>          visit_type_str(v, &sres, NULL, &errp);
> -        g_free(sres);
> +        if (error_is_set(&errp)) {
> +            error_free(errp);
> +            errp = NULL;
> +        } else {
> +            g_free(sres);
> +        }
>  
>          v = visitor_input_test_init(data, buf);
>          visit_type_EnumOne(v, &eres, NULL, &errp);
> +        if (error_is_set(&errp)) {
> +            error_free(errp);
> +            errp = NULL;
> +        }
>          visitor_input_teardown(data, NULL);
>      }
>  }
> 


-- 
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GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg

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

[Peter Maydell]

On 2 February 2013 21:37, Andreas Färber <afaerber@suse.de> wrote:
> Am 02.02.2013 22:19, schrieb Peter Maydell:
>> It's OK and expected for visitors to return errors when presented with
>> the fuzz test's random data. This means the test harness needs to
>> handle them; check for and free any error after each visitor call,
>> and only free the string returned by visit_type_str if visit_type_str
>> succeeded.
>>
>> 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].
>>
>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>> ---
>>  tests/test-string-input-visitor.c | 23 ++++++++++++++++++++++-
>>  1 file changed, 22 insertions(+), 1 deletion(-)
>>
>> diff --git a/tests/test-string-input-visitor.c b/tests/test-string-input-visitor.c
>> index f6b0093..793b334 100644
>> --- a/tests/test-string-input-visitor.c
>> +++ b/tests/test-string-input-visitor.c
>> @@ -194,20 +194,41 @@ static void test_visitor_in_fuzz(TestInputVisitorData *data,
>>
>>          v = visitor_input_test_init(data, buf);
>>          visit_type_int(v, &ires, NULL, &errp);
>> +        if (error_is_set(&errp)) {
>> +            error_free(errp);
>> +            errp = NULL;
>> +        }
>
> It seems to me the naming is bad here: errp appears to be an Error*, not
> an Error**. It would be nice to fix this within the function touched.

"Error *errp" is blessed by docs/writing-qmp-commands.txt (and
git grep 'Error \*errp' has 80 examples in the tree). I think
if I were writing this code I'd probably agree with you about the
naming, but I'm not and I don't particularly feel like changing
names somebody else has been consistent about in this source file
in the course of fixing a bug.

> Since it is an Error*, I think it was said that we should not use
> error_is_set() but err != NULL (or if you prefer, just err).
> error_is_set() is intended for **errp arguments that may be NULL.

Calling error_is_set(&some_local_err_ptr) is also in the
examples in the docs. If not doing that is the recommendation
there should be a doc comment in error.h about that.

-- PMM