[Mesa-dev] [Patch] prog_parameter.c ASAN Patch

[Maxfield, Myles]

Sorry for the double post; I received a bounce email the first time so I'm trying again.

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;
          }

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