[Mesa-dev] [PATCH] prog_parameter.c ASAN Patch
Myles C. Maxfield
myles.maxfield at gmail.com
Mon Jul 1 15:09:42 PDT 2013
Looks good to me. Thanks for fixing it up. Do the prospects look good for
getting this committed?
It would be cool if my name was attached to the patch, but since you really
ended up writing it, its fine with me if you're marked as the author.
Thanks,
Myles
On Mon, Jul 1, 2013 at 2:08 PM, Brian Paul <brianp at vmware.com> wrote:
> I took a closer look at your patch and I think it's incorrect.
>
> Note that the 'values' pointer is incremented by 4 in each loop iteration
> and size is decremented by 4. So accessing values[i*4+j] will eventually
> go out of bounds.
>
> I think something like this would work.
>
> diff --git a/src/mesa/program/prog_**parameter.c b/src/mesa/program/prog_*
> *parameter.c
> index 95b153e..1b16feb 100644
> --- a/src/mesa/program/prog_**parameter.c
> +++ b/src/mesa/program/prog_**parameter.c
> @@ -155,7 +155,17 @@ _mesa_add_parameter(struct gl_program_parameter_list
> *paramList,
>
> p->Size = size;
> p->DataType = datatype;
> if (values) {
> - COPY_4V(paramList->**ParameterValues[oldNum + i], values);
> + if (size >= 4) {
>
> + COPY_4V(paramList->**ParameterValues[oldNum + i], values);
> + }
> + else {
>
> + for (j = 0; j < size; j++) {
> + paramList->ParameterValues[**oldNum + i][j] =
> values[j];
> + }
> + for (; j < 4; j++) {
> + paramList->ParameterValues[**oldNum + i][j] = 0.0f;
>
> + }
> + }
> values += 4;
> p->Initialized = GL_TRUE;
> }
>
> -Brian
>
>
>
> On 06/19/2013 01:47 AM, Myles C. Maxfield wrote:
>
>> Any word on this?
>>
>> Thanks,
>> Myles
>>
>>
>> On Mon, Jun 17, 2013 at 12:09 PM, Myles C. Maxfield
>> <myles.maxfield at gmail.com <mailto:myles.maxfield at gmail.**com<myles.maxfield at gmail.com>>>
>> wrote:
>>
>> Sure. I was under the impression that |size| couldn't be both
>> greater than 4 and a non-multiple of 4, but I've reworked the patch
>> to incorporate this and to be a little more straightforward.
>>
>> Is the only way to replace "ASAN" with "Address Sanitizer" to change
>> the subject of this email thread?
>>
>> Anyway, here's a similar but modified patch:
>>
>> From: Myles C. Maxfield <mymax at amazon.com <mailto:mymax at amazon.com>>
>>
>> Date: Mon, 17 Jun 2013 11:50:05 -0700
>> Subject: [PATCH] Appeasing Address Sanitizer
>>
>> ---
>> src/mesa/program/prog_**parameter.c | 13 ++++++++++++-
>> 1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/mesa/program/prog_**parameter.c
>> b/src/mesa/program/prog_**parameter.c
>> index 95b153e..1d46476 100644
>> --- a/src/mesa/program/prog_**parameter.c
>> +++ b/src/mesa/program/prog_**parameter.c
>> @@ -155,7 +155,18 @@ _mesa_add_parameter(struct
>> gl_program_parameter_list *paramList,
>> p->Size = size;
>> p->DataType = datatype;
>> if (values) {
>> - COPY_4V(paramList->**ParameterValues[oldNum + i],
>> values);
>> + if (size >= (i+1)*4) {
>> + COPY_4V(paramList->**ParameterValues[oldNum + i],
>> values);
>> + } else {
>> + /* silence asan */
>> + for (j = 0; j < 4; j++) {
>> + if (i*4+j < size) {
>> + paramList->ParameterValues[**oldNum + i][j]
>> =
>> values[i*4+j];
>> + } else {
>> + paramList->ParameterValues[**oldNum +
>> i][j].f
>> = 0.0f;
>> + }
>> + }
>> + }
>> values += 4;
>> p->Initialized = GL_TRUE;
>> }
>> --
>> 1.7.12.4 (Apple Git-37)
>>
>>
>> On Mon, Jun 17, 2013 at 8:13 AM, Brian Paul <brianp at vmware.com
>> <mailto:brianp at vmware.com>> wrote:
>>
>> On 06/14/2013 05:12 PM, Myles C. Maxfield wrote:
>>
>> Sorry for the triple post; I received a bounce email the
>> first time and got sent to the spam folder the second time,
>> so I'm trying a third time.
>>
>> Hello, all. I was running Mesa with Address Sanitizer [1]
>> turned on, and found one place where ASAN pointed out a
>> read-before-initialized problem. In particular, in
>> _mesa_add_parameter, in prog_parameter.c, |values|
>> represents an array holding a variable number of values.
>> These values get copied out of the array 4 at a time with
>> the COPY_4V macro, however, the array might only contain a
>> single element. In this case, ASAN reports a
>> read-before-initialize because the last 3 of the 4 elements
>> haven't been written to yet. I was hoping to contribute a
>> patch that will silence this problem that ASAN reports. I'm
>> happy to incorporate any feedback anyone has into this patch.
>>
>> Thanks,
>> Myles C. Maxfield
>>
>> [1]https://code.google.com/p/_**_address-sanitizer/<https://code.google.com/p/__address-sanitizer/>
>> <https://code.google.com/p/**address-sanitizer/<https://code.google.com/p/address-sanitizer/>
>> >
>>
>> diff --git a/src/mesa/program/prog___**parameter.c
>> b/src/mesa/program/prog___**parameter.c
>> index 2018fa5..63915fb 100644
>> --- a/src/mesa/program/prog___**parameter.c
>> +++ b/src/mesa/program/prog___**parameter.c
>>
>> @@ -158,7 +158,17 @@ _mesa_add_parameter(struct
>> gl_program_parameter_list *paramList,
>> p->DataType = datatype;
>> p->Flags = flags;
>> if (values) {
>> - COPY_4V(paramList->__**ParameterValues[oldNum +
>>
>> i], values);
>> + if (size & 3) {
>> + for (j = 0; j < size; j++) {
>> + paramList->ParameterValues[__**oldNum +
>> i][j]
>>
>> = values[j];
>> + }
>> + /* silence asan */
>> + for (j = size; j < 4; j++) {
>> + paramList->ParameterValues[__**oldNum +
>>
>> i][j].f = 0;
>> + }
>> + } else {
>> + COPY_4V(paramList->__**ParameterValues[oldNum
>> +
>>
>> i], values);
>> + }
>> values += 4;
>> p->Initialized = GL_TRUE;
>> }
>>
>>
>> The value of 'size' can actually be greater than 4 (IIRC, and
>> the function comment are still correct). For example, for a
>> matrix, size=16. So the first for-loop should be fixed, just to
>> be safe.
>>
>> In the commit message, let's not use "ASAN" since it's not
>> obvious that it means Address Sanitizer.
>>
>> -Brian
>>
>>
>>
>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20130701/135fed6b/attachment-0001.html>
More information about the mesa-dev
mailing list