[Mesa-dev] [PATCH] mesa: Add null pointer checks before dereferencing

[Anuj Phogat]

On Thu, Jun 27, 2013 at 2:59 PM, Brian Paul <brianp at vmware.com> wrote:
> On 06/27/2013 03:31 PM, Kenneth Graunke wrote:
>>
>> On 06/27/2013 02:20 PM, Anuj Phogat wrote:
>>>
>>> Assertions are not sufficient to check for null pointers as they don't
>>> show up in release builds. So, add explicit null pointer checks in the
>>> code.
>>>
>>> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
>>> ---
>>>   src/mesa/program/prog_execute.c | 10 ++++++++++
>>>   1 file changed, 10 insertions(+)
>>>
>>> diff --git a/src/mesa/program/prog_execute.c
>>> b/src/mesa/program/prog_execute.c
>>> index b902006..1bcbf6b 100644
>>> --- a/src/mesa/program/prog_execute.c
>>> +++ b/src/mesa/program/prog_execute.c
>>> @@ -200,6 +200,8 @@ fetch_vector4(const struct prog_src_register *source,
>>>   {
>>>      const GLfloat *src = get_src_register_pointer(source, machine);
>>>      ASSERT(src);
>>> +   if (src == NULL)
>>> +      return;
>>>
>>>      if (source->Swizzle == SWIZZLE_NOOP) {
>>>         /* no swizzling */
>>> @@ -303,6 +305,8 @@ fetch_vector1(const struct prog_src_register *source,
>>>   {
>>>      const GLfloat *src = get_src_register_pointer(source, machine);
>>>      ASSERT(src);
>>> +   if (src == NULL)
>>> +      return;
>>>
>>>      result[0] = src[GET_SWZ(source->Swizzle, 0)];
>>>
>>> @@ -320,6 +324,9 @@ fetch_vector1ui(const struct prog_src_register
>>> *source,
>>>                   const struct gl_program_machine *machine)
>>>   {
>>>      const GLuint *src = (GLuint *) get_src_register_pointer(source,
>>> machine);
>>> +   ASSERT(src);
>>> +   if (src == NULL)
>>> +      return 0;
>>>      return src[GET_SWZ(source->Swizzle, 0)];
>>>   }
>>>
>>> @@ -1439,8 +1446,11 @@ _mesa_execute_program(struct gl_context * ctx,
>>>            {
>>>               const struct prog_src_register *source = &inst->SrcReg[0];
>>>               const GLfloat *src = get_src_register_pointer(source,
>>> machine);
>>> +            ASSERT(src);
>>>               GLfloat result[4];
>>>               GLuint i;
>>> +            if (src == NULL)
>>> +               return GL_FALSE;
>>>               for (i = 0; i < 4; i++) {
>>>                  const GLuint swz = GET_SWZ(source->Swizzle, i);
>>>                  if (swz == SWIZZLE_ZERO)
>>>
>>
>> I don't like this.  I would just put an abort() below the _mesa_problem
>> in get_src_register_pointer.
>
>
> For release builds I don't think that we ever want to abort/exit.
>
> I think the only time get_src_register_pointer() can return NULL is for the
> case of an invalid register file.  And we could instead return the ZeroVec
> there.
Yes. This is a better option for get_src_register_pointer(). But I
think we can't return ZeroVec (a const float*) instead of NULL
in get_dst_register_pointer(). Should we return dummyReg instead?

>
> -Brian
>