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C++: Improve isGuarded.

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This commit is contained in:
Geoffrey White
2021-04-06 17:59:22 +01:00
parent 59ff3f315b
commit 3ecd13531f
3 changed files with 10 additions and 8 deletions
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12
cpp/ql/src/Security/CWE/CWE-191/UnsignedDifferenceExpressionComparedZero.ql
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@@ -16,12 +16,16 @@ import semmle.code.cpp.valuenumbering.GlobalValueNumbering
import semmle.code.cpp.rangeanalysis.SimpleRangeAnalysis
import semmle.code.cpp.controlflow.Guards
/** Holds if `sub` is guarded by a condition which ensures that `left >= right`. */
/**
* Holds if `sub` is guarded by a condition which ensures that
* `left >= right`.
*/
pragma[noinline]
predicate isGuarded(SubExpr sub, Expr left, Expr right) {
exists(GuardCondition guard |
guard.controls(sub.getBasicBlock(), true) and
guard.ensuresLt(left, right, 0, sub.getBasicBlock(), false)
exists(GuardCondition guard, int k |
guard.controls(sub.getBasicBlock(), _) and
guard.ensuresLt(left, right, k, sub.getBasicBlock(), false) and
k >= 0
)
}

2
cpp/ql/test/query-tests/Security/CWE/CWE-191/UnsignedDifferenceExpressionComparedZero/UnsignedDifferenceExpressionComparedZero.expected
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@@ -17,8 +17,6 @@
| test.cpp:137:6:137:14 | ... > ... | Unsigned subtraction can never be negative. |
| test.cpp:146:7:146:15 | ... > ... | Unsigned subtraction can never be negative. |
| test.cpp:152:7:152:15 | ... > ... | Unsigned subtraction can never be negative. |
| test.cpp:156:7:156:15 | ... > ... | Unsigned subtraction can never be negative. |
| test.cpp:169:6:169:14 | ... > ... | Unsigned subtraction can never be negative. |
| test.cpp:182:6:182:14 | ... > ... | Unsigned subtraction can never be negative. |
| test.cpp:195:6:195:14 | ... > ... | Unsigned subtraction can never be negative. |
| test.cpp:208:6:208:14 | ... > ... | Unsigned subtraction can never be negative. |

4
cpp/ql/test/query-tests/Security/CWE/CWE-191/UnsignedDifferenceExpressionComparedZero/test.cpp
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@@ -153,7 +153,7 @@ void test8() {
// ...
}
} else {
if (a - b > 0) { // GOOD (as a > b) [FALSE POSITIVE]
if (a - b > 0) { // GOOD (as a > b)
// ...
}
}
@@ -166,7 +166,7 @@ void test8() {
if (a < b) return;
if (a - b > 0) { // GOOD (as a >= b) [FALSE POSITIVE]
if (a - b > 0) { // GOOD (as a >= b)
// ...
}
}