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C++: Make PartialDefinitionNode private and add/update comments based on review comments

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This commit is contained in:
Mathias Vorreiter Pedersen
2020-04-16 17:19:12 +02:00
parent f02feac33a
commit 62e2ffe623
2 changed files with 24 additions and 10 deletions
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18
cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll
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@@ -251,7 +251,7 @@ abstract class PostUpdateNode extends InstructionNode {
* setY(&x); // a partial definition of the object `x`. * setY(&x); // a partial definition of the object `x`.
* ``` * ```
*/ */
abstract class PartialDefinitionNode extends PostUpdateNode, TInstructionNode { } abstract private class PartialDefinitionNode extends PostUpdateNode, TInstructionNode { }
private class ExplicitFieldStoreQualifierNode extends PartialDefinitionNode { private class ExplicitFieldStoreQualifierNode extends PartialDefinitionNode {
override ChiInstruction instr; override ChiInstruction instr;
@@ -264,7 +264,7 @@ private class ExplicitFieldStoreQualifierNode extends PartialDefinitionNode {
} }
// There might be multiple `ChiInstructions` that has a particular instruction as // There might be multiple `ChiInstructions` that has a particular instruction as
// the total operand - so this definition give consistency errors in // the total operand - so this definition gives consistency errors in
// DataFlowImplConsistency::Consistency. However, it's not clear what (if any) implications // DataFlowImplConsistency::Consistency. However, it's not clear what (if any) implications
// this consistency failure has. // this consistency failure has.
override Node getPreUpdateNode() { result.asInstruction() = instr.getTotal() } override Node getPreUpdateNode() { result.asInstruction() = instr.getTotal() }
@@ -430,9 +430,23 @@ private predicate simpleInstructionLocalFlowStep(Instruction iFrom, Instruction
// for now. // for now.
iTo.getAnOperand().(ChiTotalOperand).getDef() = iFrom iTo.getAnOperand().(ChiTotalOperand).getDef() = iFrom
or or
// The next two rules allow flow from partial definitions in setters to succeeding loads in the caller.
// First, we add flow from write side-effects to non-conflated chi instructions through their
// partial operands. Consider the following example:
// ```
// void setX(Point* p, int new_x) {
// p->x = new_x;
// }
// ...
// setX(&p, taint());
// ```
// Here, a `WriteSideEffectInstruction` will provide a new definition for `p->x` after the call to
// `setX`, which will be melded into `p` through a chi instruction.
iTo.getAnOperand().(ChiPartialOperand).getDef() = iFrom.(WriteSideEffectInstruction) and iTo.getAnOperand().(ChiPartialOperand).getDef() = iFrom.(WriteSideEffectInstruction) and
not iTo.isResultConflated() not iTo.isResultConflated()
or or
// Next, we add flow from non-conflated chi instructions to loads (even when they are not precise).
// This ensures that loads of `p->x` gets data flow from the `WriteSideEffectInstruction` above.
exists(ChiInstruction chi | iFrom = chi | exists(ChiInstruction chi | iFrom = chi |
not chi.isResultConflated() and not chi.isResultConflated() and
iTo.(LoadInstruction).getSourceValueOperand().getAnyDef() = chi iTo.(LoadInstruction).getSourceValueOperand().getAnyDef() = chi

16
cpp/ql/test/library-tests/dataflow/taint-tests/taint.cpp
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@@ -85,14 +85,14 @@ void class_field_test() {
mc1.myMethod(); mc1.myMethod();
sink(mc1.a); // [FALSE POSITIVE] sink(mc1.a);
sink(mc1.b); // tainted sink(mc1.b); // tainted [NOT DETECTED with IR]
sink(mc1.c); // tainted sink(mc1.c); // tainted [NOT DETECTED with IR]
sink(mc1.d); // tainted sink(mc1.d); // tainted [NOT DETECTED with IR]
sink(mc2.a); // [FALSE POSITIVE] sink(mc2.a);
sink(mc2.b); // tainted sink(mc2.b); // tainted [NOT DETECTED with IR]
sink(mc2.c); // tainted sink(mc2.c); // tainted [NOT DETECTED with IR]
sink(mc2.d); // [FALSE POSITIVE] sink(mc2.d);
} }
// --- arrays --- // --- arrays ---