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codeql/cpp/ql/src/Critical/InconsistentNullnessTesting.ql

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/**
* @name Inconsistent null check of pointer
* @description A dereferenced pointer is not checked for nullness in this location, but it is checked in other locations. Dereferencing a null pointer leads to undefined results.
* @kind problem
* @id cpp/inconsistent-nullness-testing
* @problem.severity warning
* @security-severity 7.5
* @tags reliability
* security
* external/cwe/cwe-476
*/
import cpp
from StackVariable v, ControlFlowNode def, VariableAccess checked, VariableAccess unchecked
where
checked = v.getAnAccess() and
dereferenced(checked) and
unchecked = v.getAnAccess() and
dereferenced(unchecked) and
definitionUsePair(v, def, checked) and
definitionUsePair(v, def, unchecked) and
checkedValid(v, checked) and
not checkedValid(v, unchecked) and
not unchecked.getParent+() instanceof SizeofOperator and
forall(ControlFlowNode other | definitionUsePair(v, other, checked) |
definitionUsePair(v, other, unchecked)
)
select unchecked,
"This dereference is not guarded by a non-null check, whereas other dereferences are guarded."