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RasmusWLRasmusWL
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Merge pull request #5023 from yoff/python-unify-synthetic-post-update-nodes
Python: Only generate one post-update node, even if there are multiple reasons for doing so.
2 parents 1068ede + ae2c122 commit b6007cf

1 file changed

Lines changed: 103 additions & 82 deletions

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‎python/ql/src/semmle/python/dataflow/new/internal/DataFlowPrivate.qll‎

Lines changed: 103 additions & 82 deletions
Original file line numberDiff line numberDiff line change
@@ -11,117 +11,138 @@ private import semmle.python.essa.SsaCompute
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//--------
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predicate isExpressionNode(ControlFlowNode node) { node.getNode() instanceof Expr }
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/** A data flow node for which we should synthesise an associated pre-update node. */
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abstract class NeedsSyntheticPreUpdateNode extends Node {
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/** A label for this kind of node. This will figure in the textual representation of the synthesized pre-update node. */
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abstract string label();
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}
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/** A module collecting the different reasons for synthesising a pre-update node. */
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module syntheticPreUpdateNode {
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class SyntheticPreUpdateNode extends Node, TSyntheticPreUpdateNode {
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NeedsSyntheticPreUpdateNode post;
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class SyntheticPreUpdateNode extends Node, TSyntheticPreUpdateNode {
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NeedsSyntheticPreUpdateNode post;
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SyntheticPreUpdateNode() { this = TSyntheticPreUpdateNode(post) }
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SyntheticPreUpdateNode() { this = TSyntheticPreUpdateNode(post) }
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/** Gets the node for which this is a synthetic pre-update node. */
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Node getPostUpdateNode() { result = post }
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/** Gets the node for which this is a synthetic pre-update node. */
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Node getPostUpdateNode() { result = post }
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override string toString() { result = "[pre " + post.label() + "] " + post.toString() }
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override string toString() { result = "[pre " + post.label() + "] " + post.toString() }
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override Scope getScope() { result = post.getScope() }
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override Scope getScope() { result = post.getScope() }
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override Location getLocation() { result = post.getLocation() }
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}
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override Location getLocation() { result = post.getLocation() }
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}
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/** A data flow node for which we should synthesise an associated pre-update node. */
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class NeedsSyntheticPreUpdateNode extends PostUpdateNode {
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NeedsSyntheticPreUpdateNode() { this = objectCreationNode() }
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override Node getPreUpdateNode() { result.(SyntheticPreUpdateNode).getPostUpdateNode() = this }
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/**
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* A label for this kind of node. This will figure in the textual representation of the synthesized pre-update node.
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*
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* There is currently only one reason for needing a pre-update node, so we always use that as the label.
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*/
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string label() { result = "objCreate" }
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}
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/** A data flow node for which we should synthesise an associated post-update node. */
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abstract class NeedsSyntheticPostUpdateNode extends Node {
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/** A label for this kind of node. This will figure in the textual representation of the synthesized post-update node. */
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abstract string label();
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/**
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* Calls to constructors are treated as post-update nodes for the synthesized argument
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* that is mapped to the `self` parameter. That way, constructor calls represent the value of the
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* object after the constructor (currently only `__init__`) has run.
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*/
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CfgNode objectCreationNode() { result.getNode().(CallNode) = any(ClassCall c).getNode() }
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}
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/** An argument might have its value changed as a result of a call. */
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class ArgumentPreUpdateNode extends NeedsSyntheticPostUpdateNode, ArgumentNode {
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// Certain arguments, such as implicit self arguments are already post-update nodes
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// and should not have an extra node synthesised.
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ArgumentPreUpdateNode() {
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this = any(FunctionCall c).getArg(_)
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import syntheticPreUpdateNode
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/** A module collecting the different reasons for synthesising a post-update node. */
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module syntheticPostUpdateNode {
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/** A post-update node is synthesized for all nodes which satisfy `NeedsSyntheticPostUpdateNode`. */
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class SyntheticPostUpdateNode extends PostUpdateNode, TSyntheticPostUpdateNode {
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NeedsSyntheticPostUpdateNode pre;
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SyntheticPostUpdateNode() { this = TSyntheticPostUpdateNode(pre) }
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override Node getPreUpdateNode() { result = pre }
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override string toString() { result = "[post " + pre.label() + "] " + pre.toString() }
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override Scope getScope() { result = pre.getScope() }
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override Location getLocation() { result = pre.getLocation() }
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}
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/** A data flow node for which we should synthesise an associated post-update node. */
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class NeedsSyntheticPostUpdateNode extends Node {
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NeedsSyntheticPostUpdateNode() {
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this = argumentPreUpdateNode()
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or
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this = storePreUpdateNode()
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or
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this = readPreUpdateNode()
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}
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/**
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* A label for this kind of node. This will figure in the textual representation of the synthesized post-update node.
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* We favour being an arguments as the reason for the post-update node in case multiple reasons apply.
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*/
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string label() {
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if this = argumentPreUpdateNode()
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then result = "arg"
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else
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if this = storePreUpdateNode()
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then result = "store"
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else result = "read"
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}
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}
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/**
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* An argument might have its value changed as a result of a call.
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* Certain arguments, such as implicit self arguments are already post-update nodes
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* and should not have an extra node synthesised.
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*/
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ArgumentNode argumentPreUpdateNode() {
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result = any(FunctionCall c).getArg(_)
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or
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// Avoid argument 0 of method calls as those have read post-update nodes.
49-
exists(MethodCall c, int n | n > 0 | this = c.getArg(n))
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exists(MethodCall c, int n | n > 0 | result = c.getArg(n))
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or
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this = any(SpecialCall c).getArg(_)
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result = any(SpecialCall c).getArg(_)
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or
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// Avoid argument 0 of class calls as those have non-synthetic post-update nodes.
54-
exists(ClassCall c, int n | n > 0 | this = c.getArg(n))
110+
exists(ClassCall c, int n | n > 0 | result = c.getArg(n))
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}
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override string label() { result = "arg" }
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}
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/** An object might have its value changed after a store. */
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class StorePreUpdateNode extends NeedsSyntheticPostUpdateNode, CfgNode {
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StorePreUpdateNode() {
113+
/** An object might have its value changed after a store. */
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CfgNode storePreUpdateNode() {
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exists(Attribute a |
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node = a.getObject().getAFlowNode() and
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result.getNode() = a.getObject().getAFlowNode() and
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a.getCtx() instanceof Store
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)
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}
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override string label() { result = "store" }
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}
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/**
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* A node marking the state change of an object after a read.
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*
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* A reverse read happens when the result of a read is modified, e.g. in
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* ```python
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* l = [ mutable ]
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* l[0].mutate()
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* ```
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* we may now have changed the content of `l`. To track this, there must be
81-
* a postupdate node for `l`.
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*/
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class ReadPreUpdateNode extends NeedsSyntheticPostUpdateNode, CfgNode {
84-
ReadPreUpdateNode() {
121+
/**
122+
* A node marking the state change of an object after a read.
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*
124+
* A reverse read happens when the result of a read is modified, e.g. in
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* ```python
126+
* l = [ mutable ]
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* l[0].mutate()
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* ```
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* we may now have changed the content of `l`. To track this, there must be
130+
* a postupdate node for `l`.
131+
*/
132+
CfgNode readPreUpdateNode() {
85133
exists(Attribute a |
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node = a.getObject().getAFlowNode() and
134+
result.getNode() = a.getObject().getAFlowNode() and
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a.getCtx() instanceof Load
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)
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or
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node = any(SubscriptNode s).getObject()
138+
result.getNode() = any(SubscriptNode s).getObject()
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or
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node.getNode() = any(Call call).getKwargs()
140+
// The dictionary argument is read from if the callable has parameters matching the keys.
141+
result.getNode().getNode() = any(Call call).getKwargs()
93142
}
94-
95-
override string label() { result = "read" }
96143
}
97144

98-
/** A post-update node is synthesized for all nodes which satisfy `NeedsSyntheticPostUpdateNode`. */
99-
class SyntheticPostUpdateNode extends PostUpdateNode, TSyntheticPostUpdateNode {
100-
NeedsSyntheticPostUpdateNode pre;
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SyntheticPostUpdateNode() { this = TSyntheticPostUpdateNode(pre) }
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override Node getPreUpdateNode() { result = pre }
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override string toString() { result = "[post " + pre.label() + "] " + pre.toString() }
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override Scope getScope() { result = pre.getScope() }
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override Location getLocation() { result = pre.getLocation() }
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}
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/**
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* Calls to constructors are treated as post-update nodes for the synthesized argument
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* that is mapped to the `self` parameter. That way, constructor calls represent the value of the
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* object after the constructor (currently only `__init__`) has run.
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*/
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class ObjectCreationNode extends PostUpdateNode, NeedsSyntheticPreUpdateNode, CfgNode {
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ObjectCreationNode() { node.(CallNode) = any(ClassCall c).getNode() }
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override Node getPreUpdateNode() { result.(SyntheticPreUpdateNode).getPostUpdateNode() = this }
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override string label() { result = "objCreate" }
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}
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import syntheticPostUpdateNode
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class DataFlowExpr = Expr;
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