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C++: Fix ArrayExpr FPs in cpp/double-free #16749

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Merged
merged 5 commits into from
Jun 13, 2024
Merged

C++: Fix ArrayExpr FPs in cpp/double-free #16749

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eec2592
C++: Add another FP test. We already have tests for this, but it does…
MathiasVP Jun 13, 2024
4079de1
C++: Fix FP by also excluding indirections of array expressions.
MathiasVP Jun 13, 2024
bcabc88
C++: Accept test changes.
MathiasVP Jun 13, 2024
83108e3
C++: Add change note.
MathiasVP Jun 13, 2024
4bbeda0
C++: Fix change note naming.
MathiasVP Jun 13, 2024
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0 ...change-notes/2024-10-06-builtin-expect.md → ...change-notes/2024-06-10-builtin-expect.md
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4 changes: 4 additions & 0 deletions cpp/ql/lib/change-notes/2024-06-13-double-free.md
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@@ -0,0 +1,4 @@
---
category: minorAnalysis
---
* The queries "Potential double free" (`cpp/double-free`) and "Potential use after free" (`cpp/use-after-free`) now produce fewer false positives.
2 changes: 1 addition & 1 deletion cpp/ql/lib/semmle/code/cpp/security/flowafterfree/FlowAfterFree.qll
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Expand Up @@ -95,7 +95,7 @@ module FlowFromFree<FlowFromFreeParamSig P> {
e = any(StoreInstruction store).getDestinationAddress().getUnconvertedResultExpression()
)
or
n.asExpr() instanceof ArrayExpr
[n.asExpr(), n.asIndirectExpr()] instanceof ArrayExpr
}
}

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39 changes: 0 additions & 39 deletions cpp/ql/test/query-tests/Critical/MemoryFreed/DoubleFree.expected
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Expand Up @@ -13,21 +13,6 @@ edges
| test_free.cpp:207:10:207:10 | pointer to free output argument | test_free.cpp:209:10:209:10 | a | provenance | |
| test_free.cpp:301:12:301:14 | pointer to g_free output argument | test_free.cpp:302:12:302:14 | buf | provenance | |
| test_free.cpp:319:16:319:16 | pointer to operator delete output argument | test_free.cpp:322:12:322:12 | a | provenance | |
| test_free.cpp:343:12:343:24 | *access to array [post update] [ptr] | test_free.cpp:344:12:344:24 | *access to array [ptr] | provenance | |
| test_free.cpp:343:12:343:24 | *access to array [post update] [ptr] | test_free.cpp:345:12:345:24 | *access to array [ptr] | provenance | |
| test_free.cpp:343:12:343:24 | *access to array [post update] [ptr] | test_free.cpp:346:12:346:24 | *access to array [ptr] | provenance | |
| test_free.cpp:343:26:343:28 | pointer to operator delete output argument | test_free.cpp:343:12:343:24 | *access to array [post update] [ptr] | provenance | |
| test_free.cpp:344:12:344:24 | *access to array [post update] [ptr] | test_free.cpp:345:12:345:24 | *access to array [ptr] | provenance | |
| test_free.cpp:344:12:344:24 | *access to array [post update] [ptr] | test_free.cpp:346:12:346:24 | *access to array [ptr] | provenance | |
| test_free.cpp:344:12:344:24 | *access to array [ptr] | test_free.cpp:344:26:344:28 | ptr | provenance | |
| test_free.cpp:344:26:344:28 | pointer to operator delete output argument | test_free.cpp:344:12:344:24 | *access to array [post update] [ptr] | provenance | |
| test_free.cpp:345:12:345:24 | *access to array [post update] [ptr] | test_free.cpp:346:12:346:24 | *access to array [ptr] | provenance | |
| test_free.cpp:345:12:345:24 | *access to array [ptr] | test_free.cpp:345:26:345:28 | ptr | provenance | |
| test_free.cpp:345:12:345:24 | *access to array [ptr] | test_free.cpp:345:26:345:28 | ptr | provenance | |
| test_free.cpp:345:26:345:28 | pointer to operator delete output argument | test_free.cpp:345:12:345:24 | *access to array [post update] [ptr] | provenance | |
| test_free.cpp:346:12:346:24 | *access to array [ptr] | test_free.cpp:346:26:346:28 | ptr | provenance | |
| test_free.cpp:346:12:346:24 | *access to array [ptr] | test_free.cpp:346:26:346:28 | ptr | provenance | |
| test_free.cpp:346:12:346:24 | *access to array [ptr] | test_free.cpp:346:26:346:28 | ptr | provenance | |
nodes
| test_free.cpp:11:10:11:10 | pointer to free output argument | semmle.label | pointer to free output argument |
| test_free.cpp:14:10:14:10 | a | semmle.label | a |
Expand Down Expand Up @@ -57,24 +42,6 @@ nodes
| test_free.cpp:302:12:302:14 | buf | semmle.label | buf |
| test_free.cpp:319:16:319:16 | pointer to operator delete output argument | semmle.label | pointer to operator delete output argument |
| test_free.cpp:322:12:322:12 | a | semmle.label | a |
| test_free.cpp:343:12:343:24 | *access to array [post update] [ptr] | semmle.label | *access to array [post update] [ptr] |
| test_free.cpp:343:26:343:28 | pointer to operator delete output argument | semmle.label | pointer to operator delete output argument |
| test_free.cpp:344:12:344:24 | *access to array [post update] [ptr] | semmle.label | *access to array [post update] [ptr] |
| test_free.cpp:344:12:344:24 | *access to array [ptr] | semmle.label | *access to array [ptr] |
| test_free.cpp:344:26:344:28 | pointer to operator delete output argument | semmle.label | pointer to operator delete output argument |
| test_free.cpp:344:26:344:28 | ptr | semmle.label | ptr |
| test_free.cpp:345:12:345:24 | *access to array [post update] [ptr] | semmle.label | *access to array [post update] [ptr] |
| test_free.cpp:345:12:345:24 | *access to array [ptr] | semmle.label | *access to array [ptr] |
| test_free.cpp:345:12:345:24 | *access to array [ptr] | semmle.label | *access to array [ptr] |
| test_free.cpp:345:26:345:28 | pointer to operator delete output argument | semmle.label | pointer to operator delete output argument |
| test_free.cpp:345:26:345:28 | ptr | semmle.label | ptr |
| test_free.cpp:345:26:345:28 | ptr | semmle.label | ptr |
| test_free.cpp:346:12:346:24 | *access to array [ptr] | semmle.label | *access to array [ptr] |
| test_free.cpp:346:12:346:24 | *access to array [ptr] | semmle.label | *access to array [ptr] |
| test_free.cpp:346:12:346:24 | *access to array [ptr] | semmle.label | *access to array [ptr] |
| test_free.cpp:346:26:346:28 | ptr | semmle.label | ptr |
| test_free.cpp:346:26:346:28 | ptr | semmle.label | ptr |
| test_free.cpp:346:26:346:28 | ptr | semmle.label | ptr |
subpaths
#select
| test_free.cpp:14:10:14:10 | a | test_free.cpp:11:10:11:10 | pointer to free output argument | test_free.cpp:14:10:14:10 | a | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:14:10:14:10 | a | a | test_free.cpp:11:5:11:8 | call to free | call to free |
Expand All @@ -91,9 +58,3 @@ subpaths
| test_free.cpp:209:10:209:10 | a | test_free.cpp:207:10:207:10 | pointer to free output argument | test_free.cpp:209:10:209:10 | a | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:209:10:209:10 | a | a | test_free.cpp:207:5:207:8 | call to free | call to free |
| test_free.cpp:302:12:302:14 | buf | test_free.cpp:301:12:301:14 | pointer to g_free output argument | test_free.cpp:302:12:302:14 | buf | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:302:12:302:14 | buf | buf | test_free.cpp:301:5:301:10 | call to g_free | call to g_free |
| test_free.cpp:322:12:322:12 | a | test_free.cpp:319:16:319:16 | pointer to operator delete output argument | test_free.cpp:322:12:322:12 | a | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:322:12:322:12 | a | a | test_free.cpp:319:9:319:16 | delete | delete |
| test_free.cpp:344:26:344:28 | ptr | test_free.cpp:343:26:343:28 | pointer to operator delete output argument | test_free.cpp:344:26:344:28 | ptr | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:344:26:344:28 | ptr | ptr | test_free.cpp:343:5:343:28 | delete | delete |
| test_free.cpp:345:26:345:28 | ptr | test_free.cpp:343:26:343:28 | pointer to operator delete output argument | test_free.cpp:345:26:345:28 | ptr | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:345:26:345:28 | ptr | ptr | test_free.cpp:343:5:343:28 | delete | delete |
| test_free.cpp:345:26:345:28 | ptr | test_free.cpp:344:26:344:28 | pointer to operator delete output argument | test_free.cpp:345:26:345:28 | ptr | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:345:26:345:28 | ptr | ptr | test_free.cpp:344:5:344:28 | delete | delete |
| test_free.cpp:346:26:346:28 | ptr | test_free.cpp:343:26:343:28 | pointer to operator delete output argument | test_free.cpp:346:26:346:28 | ptr | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:346:26:346:28 | ptr | ptr | test_free.cpp:343:5:343:28 | delete | delete |
| test_free.cpp:346:26:346:28 | ptr | test_free.cpp:344:26:344:28 | pointer to operator delete output argument | test_free.cpp:346:26:346:28 | ptr | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:346:26:346:28 | ptr | ptr | test_free.cpp:344:5:344:28 | delete | delete |
| test_free.cpp:346:26:346:28 | ptr | test_free.cpp:345:26:345:28 | pointer to operator delete output argument | test_free.cpp:346:26:346:28 | ptr | Memory pointed to by $@ may already have been freed by $@. | test_free.cpp:346:26:346:28 | ptr | ptr | test_free.cpp:345:5:345:28 | delete | delete |
2 changes: 2 additions & 0 deletions cpp/ql/test/query-tests/Critical/MemoryFreed/MemoryFreed.expected
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Expand Up @@ -115,6 +115,8 @@
| test_free.cpp:344:26:344:28 | ptr |
| test_free.cpp:345:26:345:28 | ptr |
| test_free.cpp:346:26:346:28 | ptr |
| test_free.cpp:356:19:356:19 | a |
| test_free.cpp:357:19:357:19 | a |
| virtual.cpp:18:10:18:10 | a |
| virtual.cpp:19:10:19:10 | c |
| virtual.cpp:38:10:38:10 | b |
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17 changes: 14 additions & 3 deletions cpp/ql/test/query-tests/Critical/MemoryFreed/test_free.cpp
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Expand Up @@ -341,7 +341,18 @@ struct PtrContainer {

void test_array(PtrContainer *containers) {
delete containers[0].ptr; // GOOD
delete containers[1].ptr; // GOOD [FALSE POSITIVE]
delete containers[2].ptr; // GOOD [FALSE POSITIVE]
delete containers[2].ptr; // BAD (double free)
delete containers[1].ptr; // GOOD
delete containers[2].ptr; // GOOD
delete containers[2].ptr; // BAD (double free) [NOT DETECTED]
}

struct E {
struct EC {
int* a;
} ec[2];
};

void test(E* e) {
free(e->ec[0].a);
free(e->ec[1].a); // GOOD
}