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/
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
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