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Merged
jbj merged 5 commits into from
Apr 23, 2020
Merged

C++: Add PostUpdateNode for updates to structs with no chi instructions #3295

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6fca23b
C++: Demonstrate lack of flow through single-field structs
MathiasVP Apr 20, 2020
a6e619c
C++: Add field flow through single-field structs and accept tests
MathiasVP Apr 20, 2020
e0cd595
C++: Reduce intermediate tuple counts
MathiasVP Apr 20, 2020
8be1bfe
C++: Add comments and accept expected dataflow sanity failures
MathiasVP Apr 20, 2020
a49d22e
C++: Fix join ordering
MathiasVP Apr 21, 2020
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26 changes: 20 additions & 6 deletions cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowPrivate.qll
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Expand Up @@ -180,12 +180,16 @@ private class ArrayContent extends Content, TArrayContent {
override Type getType() { none() }
}

/**
* Holds if data can flow from `node1` to `node2` via an assignment to `f`.
* Thus, `node2` references an object with a field `f` that contains the
* value of `node1`.
*/
predicate storeStep(Node node1, Content f, PostUpdateNode node2) {
private predicate storeStepNoChi(Node node1, Content f, PostUpdateNode node2) {
exists(FieldAddressInstruction fa, StoreInstruction store |
store = node2.asInstruction() and
store.getDestinationAddress() = fa and
store.getSourceValue() = node1.asInstruction() and
f.(FieldContent).getField() = fa.getField()
)
}

private predicate storeStepChi(Node node1, Content f, PostUpdateNode node2) {
exists(FieldAddressInstruction fa, StoreInstruction store |
node1.asInstruction() = store and
store.getDestinationAddress() = fa and
Expand All @@ -194,6 +198,16 @@ predicate storeStep(Node node1, Content f, PostUpdateNode node2) {
)
}

/**
* Holds if data can flow from `node1` to `node2` via an assignment to `f`.
* Thus, `node2` references an object with a field `f` that contains the
* value of `node1`.
*/
predicate storeStep(Node node1, Content f, PostUpdateNode node2) {
storeStepNoChi(node1, f, node2) or
storeStepChi(node1, f, node2)
}

/**
* Holds if data can flow from `node1` to `node2` via a read of `f`.
* Thus, `node1` references an object with a field `f` whose value ends up in
Expand Down
36 changes: 36 additions & 0 deletions cpp/ql/src/semmle/code/cpp/ir/dataflow/internal/DataFlowUtil.qll
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Expand Up @@ -270,6 +270,25 @@ private class ExplicitFieldStoreQualifierNode extends PartialDefinitionNode {
override Node getPreUpdateNode() { result.asInstruction() = instr.getTotal() }
}

/**
* Not every store instruction generates a chi instruction that we can attach a PostUpdateNode to.
* For instance, an update to a field of a struct containing only one field. For these cases we
* attach the PostUpdateNode to the store instruction. There's no obvious pre update node for this case
* (as the entire memory is updated), so `getPreUpdateNode` is implemented as `none()`.
*/
private class ExplicitSingleFieldStoreQualifierNode extends PartialDefinitionNode {
override StoreInstruction instr;

ExplicitSingleFieldStoreQualifierNode() {
exists(FieldAddressInstruction field |
field = instr.getDestinationAddress() and
not exists(ChiInstruction chi | chi.getPartial() = instr)
)
}

override Node getPreUpdateNode() { none() }
}

/**
* A node that represents the value of a variable after a function call that
* may have changed the variable because it's passed by reference.
Expand Down Expand Up @@ -404,6 +423,15 @@ predicate simpleLocalFlowStep(Node nodeFrom, Node nodeTo) {
simpleInstructionLocalFlowStep(nodeFrom.asInstruction(), nodeTo.asInstruction())
}

pragma[noinline]
private predicate getFieldSizeOfClass(Class c, Type type, int size) {
exists(Field f |
f.getDeclaringType() = c and
f.getType() = type and
type.getSize() = size
)
}

cached
private predicate simpleInstructionLocalFlowStep(Instruction iFrom, Instruction iTo) {
iTo.(CopyInstruction).getSourceValue() = iFrom
Expand Down Expand Up @@ -452,6 +480,14 @@ private predicate simpleInstructionLocalFlowStep(Instruction iFrom, Instruction
iTo.(LoadInstruction).getSourceValueOperand().getAnyDef() = chi
)
or
// Flow from stores to structs with a single field to a load of that field.
iTo.(LoadInstruction).getSourceValueOperand().getAnyDef() = iFrom and
exists(int size, Type type |
type = iFrom.getResultType() and
iTo.getResultType().getSize() = size and
getFieldSizeOfClass(iTo.getResultType(), type, size)
)
or
// Flow through modeled functions
modelFlow(iFrom, iTo)
}
Expand Down
1 change: 1 addition & 0 deletions cpp/ql/test/library-tests/dataflow/fields/dataflow-ir-consistency.expected
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Expand Up @@ -19,6 +19,7 @@ unreachableNodeCCtx
localCallNodes
postIsNotPre
postHasUniquePre
| simple.cpp:65:5:65:22 | Store | PostUpdateNode should have one pre-update node but has 0. |
uniquePostUpdate
postIsInSameCallable
reverseRead
Expand Down
10 changes: 10 additions & 0 deletions cpp/ql/test/library-tests/dataflow/fields/flow.expected
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Expand Up @@ -221,6 +221,10 @@ edges
| simple.cpp:48:9:48:9 | g [b_] | simple.cpp:26:15:26:15 | f [b_] |
| simple.cpp:51:9:51:9 | h [a_] | simple.cpp:26:15:26:15 | f [a_] |
| simple.cpp:51:9:51:9 | h [b_] | simple.cpp:26:15:26:15 | f [b_] |
| simple.cpp:65:5:65:5 | a [post update] [i] | simple.cpp:67:10:67:11 | a2 [i] |
| simple.cpp:65:5:65:22 | ... = ... | simple.cpp:65:5:65:5 | a [post update] [i] |
| simple.cpp:65:11:65:20 | call to user_input | simple.cpp:65:5:65:22 | ... = ... |
| simple.cpp:67:10:67:11 | a2 [i] | simple.cpp:67:13:67:13 | i |
| struct_init.c:14:24:14:25 | ab [a] | struct_init.c:15:8:15:9 | ab [a] |
| struct_init.c:15:8:15:9 | ab [a] | struct_init.c:15:12:15:12 | a |
| struct_init.c:20:17:20:36 | {...} [a] | struct_init.c:22:8:22:9 | ab [a] |
Expand Down Expand Up @@ -504,6 +508,11 @@ nodes
| simple.cpp:48:9:48:9 | g [b_] | semmle.label | g [b_] |
| simple.cpp:51:9:51:9 | h [a_] | semmle.label | h [a_] |
| simple.cpp:51:9:51:9 | h [b_] | semmle.label | h [b_] |
| simple.cpp:65:5:65:5 | a [post update] [i] | semmle.label | a [post update] [i] |
| simple.cpp:65:5:65:22 | ... = ... | semmle.label | ... = ... |
| simple.cpp:65:11:65:20 | call to user_input | semmle.label | call to user_input |
| simple.cpp:67:10:67:11 | a2 [i] | semmle.label | a2 [i] |
| simple.cpp:67:13:67:13 | i | semmle.label | i |
| struct_init.c:14:24:14:25 | ab [a] | semmle.label | ab [a] |
| struct_init.c:15:8:15:9 | ab [a] | semmle.label | ab [a] |
| struct_init.c:15:12:15:12 | a | semmle.label | a |
Expand Down Expand Up @@ -580,6 +589,7 @@ nodes
| simple.cpp:28:12:28:12 | call to a | simple.cpp:41:12:41:21 | call to user_input | simple.cpp:28:12:28:12 | call to a | call to a flows from $@ | simple.cpp:41:12:41:21 | call to user_input | call to user_input |
| simple.cpp:29:12:29:12 | call to b | simple.cpp:40:12:40:21 | call to user_input | simple.cpp:29:12:29:12 | call to b | call to b flows from $@ | simple.cpp:40:12:40:21 | call to user_input | call to user_input |
| simple.cpp:29:12:29:12 | call to b | simple.cpp:42:12:42:21 | call to user_input | simple.cpp:29:12:29:12 | call to b | call to b flows from $@ | simple.cpp:42:12:42:21 | call to user_input | call to user_input |
| simple.cpp:67:13:67:13 | i | simple.cpp:65:11:65:20 | call to user_input | simple.cpp:67:13:67:13 | i | i flows from $@ | simple.cpp:65:11:65:20 | call to user_input | call to user_input |
| struct_init.c:15:12:15:12 | a | struct_init.c:20:20:20:29 | call to user_input | struct_init.c:15:12:15:12 | a | a flows from $@ | struct_init.c:20:20:20:29 | call to user_input | call to user_input |
| struct_init.c:15:12:15:12 | a | struct_init.c:27:7:27:16 | call to user_input | struct_init.c:15:12:15:12 | a | a flows from $@ | struct_init.c:27:7:27:16 | call to user_input | call to user_input |
| struct_init.c:15:12:15:12 | a | struct_init.c:40:20:40:29 | call to user_input | struct_init.c:15:12:15:12 | a | a flows from $@ | struct_init.c:40:20:40:29 | call to user_input | call to user_input |
Expand Down
8 changes: 8 additions & 0 deletions cpp/ql/test/library-tests/dataflow/fields/ir-flow.expected
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Expand Up @@ -25,6 +25,9 @@ edges
| aliasing.cpp:79:11:79:20 | call to user_input | aliasing.cpp:80:12:80:13 | m1 |
| aliasing.cpp:86:10:86:19 | call to user_input | aliasing.cpp:87:12:87:13 | m1 |
| aliasing.cpp:92:12:92:21 | call to user_input | aliasing.cpp:93:12:93:13 | m1 |
| simple.cpp:65:5:65:22 | Store [i] | simple.cpp:66:12:66:12 | Store [i] |
| simple.cpp:65:11:65:20 | call to user_input | simple.cpp:65:5:65:22 | Store [i] |
| simple.cpp:66:12:66:12 | Store [i] | simple.cpp:67:13:67:13 | i |
| struct_init.c:20:20:20:29 | call to user_input | struct_init.c:22:11:22:11 | a |
| struct_init.c:27:7:27:16 | call to user_input | struct_init.c:31:23:31:23 | a |
nodes
Expand Down Expand Up @@ -63,6 +66,10 @@ nodes
| aliasing.cpp:87:12:87:13 | m1 | semmle.label | m1 |
| aliasing.cpp:92:12:92:21 | call to user_input | semmle.label | call to user_input |
| aliasing.cpp:93:12:93:13 | m1 | semmle.label | m1 |
| simple.cpp:65:5:65:22 | Store [i] | semmle.label | Store [i] |
| simple.cpp:65:11:65:20 | call to user_input | semmle.label | call to user_input |
| simple.cpp:66:12:66:12 | Store [i] | semmle.label | Store [i] |
| simple.cpp:67:13:67:13 | i | semmle.label | i |
| struct_init.c:20:20:20:29 | call to user_input | semmle.label | call to user_input |
| struct_init.c:22:11:22:11 | a | semmle.label | a |
| struct_init.c:27:7:27:16 | call to user_input | semmle.label | call to user_input |
Expand All @@ -78,5 +85,6 @@ nodes
| aliasing.cpp:80:12:80:13 | m1 | aliasing.cpp:79:11:79:20 | call to user_input | aliasing.cpp:80:12:80:13 | m1 | m1 flows from $@ | aliasing.cpp:79:11:79:20 | call to user_input | call to user_input |
| aliasing.cpp:87:12:87:13 | m1 | aliasing.cpp:86:10:86:19 | call to user_input | aliasing.cpp:87:12:87:13 | m1 | m1 flows from $@ | aliasing.cpp:86:10:86:19 | call to user_input | call to user_input |
| aliasing.cpp:93:12:93:13 | m1 | aliasing.cpp:92:12:92:21 | call to user_input | aliasing.cpp:93:12:93:13 | m1 | m1 flows from $@ | aliasing.cpp:92:12:92:21 | call to user_input | call to user_input |
| simple.cpp:67:13:67:13 | i | simple.cpp:65:11:65:20 | call to user_input | simple.cpp:67:13:67:13 | i | i flows from $@ | simple.cpp:65:11:65:20 | call to user_input | call to user_input |
| struct_init.c:22:11:22:11 | a | struct_init.c:20:20:20:29 | call to user_input | struct_init.c:22:11:22:11 | a | a flows from $@ | struct_init.c:20:20:20:29 | call to user_input | call to user_input |
| struct_init.c:31:23:31:23 | a | struct_init.c:27:7:27:16 | call to user_input | struct_init.c:31:23:31:23 | a | a flows from $@ | struct_init.c:27:7:27:16 | call to user_input | call to user_input |
14 changes: 14 additions & 0 deletions cpp/ql/test/library-tests/dataflow/fields/simple.cpp
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Expand Up @@ -53,4 +53,18 @@ void foo()
// Nothing should alert
bar(i);
}

struct A
{
int i;
};

void single_field_test()
{
A a;
a.i = user_input();
A a2 = a;
sink(a2.i);
}

} // namespace Simple
4 changes: 4 additions & 0 deletions cpp/ql/test/library-tests/syntax-zoo/dataflow-ir-consistency.expected
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Expand Up @@ -788,6 +788,10 @@ unreachableNodeCCtx
localCallNodes
postIsNotPre
postHasUniquePre
| assignexpr.cpp:9:2:9:12 | Store | PostUpdateNode should have one pre-update node but has 0. |
| bad_asts.cpp:15:10:15:12 | Store | PostUpdateNode should have one pre-update node but has 0. |
| file://:0:0:0:0 | Store | PostUpdateNode should have one pre-update node but has 0. |
| ir.cpp:531:14:531:14 | Store | PostUpdateNode should have one pre-update node but has 0. |
uniquePostUpdate
postIsInSameCallable
reverseRead
Expand Down