Disabling label-unioning in dataflow sanitizer?

Hi guys,

Does anyone know if clang’s dataflow sanitizer supports the following option, or if there are plans to?

Right now (clang 3.6), it seems that when two or more inputs of a given operation carry different labels, the resulting value is tagged with the union of those labels. But I’m interested in a different kind of analysis, where I track the pristine flow of a value. So in my analysis, when an operation does anything other than cleanly propagate an input value to its output, I want the output to be unlabeled.

For example, if we have:
int c = a + b;

Then I want ‘c’ to be have a dfas label if and only if ‘a’ and ‘b’ both have the same label.

Thanks,
Christian

Sorry, that example wasn’t correct. I should have written:

int c = a + b; // c will never have a label in this case.
int d = a; // d will always get a’s label

Hi Christian,

Can't you treat all union labels as being unlabelled? You can see what
kind of label you have using the dfsan_get_label_info() function.

Peter