github · jsinglet · Oct 19, 2022 · Oct 14, 2022 · Oct 17, 2022 · Oct 17, 2022
diff --git a/c/cert/src/rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.md b/c/cert/src/rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.md
@@ -0,0 +1,98 @@
+# CON39-C: Do not join or detach a thread that was previously joined or detached
+
+This query implements the CERT-C rule CON39-C:
+
+> Do not join or detach a thread that was previously joined or detached
+
+
+## Description
+
+The C Standard, 7.26.5.6 \[[ISO/IEC 9899:2011](https://wiki.sei.cmu.edu/confluence/display/c/AA.+Bibliography#AA.Bibliography-ISO-IEC9899-2011)\], states that a thread shall not be joined once it was previously joined or detached. Similarly, subclause 7.26.5.3 states that a thread shall not be detached once it was previously joined or detached. Violating either of these subclauses results in [undefined behavior](https://wiki.sei.cmu.edu/confluence/display/c/BB.+Definitions#BB.Definitions-undefinedbehavior).
+
+## Noncompliant Code Example
+
+This noncompliant code example detaches a thread that is later joined.
+
+```cpp
+#include <stddef.h>
+#include <threads.h>
+
+int thread_func(void *arg) {
+  /* Do work */
+  thrd_detach(thrd_current());
+  return 0;
+}
+
+int main(void) {
+  thrd_t t;
+
+  if (thrd_success != thrd_create(&t, thread_func, NULL)) {
+    /* Handle error */
+    return 0;
+  }
+
+  if (thrd_success != thrd_join(t, 0)) {
+    /* Handle error */
+    return 0;
+  }
+  return 0;
+}
+```
+
+## Compliant Solution
+
+This compliant solution does not detach the thread. Its resources are released upon successfully joining with the main thread:
+
+```cpp
+#include <stddef.h>
+#include <threads.h>
+
+int thread_func(void *arg) {
+  /* Do work */
+  return 0;
+}
+
+int main(void) {
+  thrd_t t;
+
+  if (thrd_success != thrd_create(&t, thread_func, NULL)) {
+    /* Handle error */
+    return 0;
+  }
+
+  if (thrd_success != thrd_join(t, 0)) {
+    /* Handle error */
+    return 0;
+  }
+  return 0;
+} 
+```
+
+## Risk Assessment
+
+Joining or detaching a previously joined or detached thread is [undefined behavior](https://wiki.sei.cmu.edu/confluence/display/c/BB.+Definitions#BB.Definitions-undefinedbehavior).
+
+<table> <tbody> <tr> <th> Rule </th> <th> Severity </th> <th> Likelihood </th> <th> Remediation Cost </th> <th> Priority </th> <th> Level </th> </tr> <tr> <td> CON39-C </td> <td> Low </td> <td> Likely </td> <td> Medium </td> <td> <strong>P6</strong> </td> <td> <strong>L2</strong> </td> </tr> </tbody> </table>
+
+
+## Automated Detection
+
+<table> <tbody> <tr> <th> Tool </th> <th> Version </th> <th> Checker </th> <th> Description </th> </tr> <tr> <td> <a> Astrée </a> </td> <td> 22.04 </td> <td> </td> <td> Supported, but no explicit checker </td> </tr> <tr> <td> <a> CodeSonar </a> </td> <td> 7.1p0 </td> <td> <strong>CONCURRENCY.TNJ</strong> </td> <td> Thread is not Joinable </td> </tr> <tr> <td> <a> Helix QAC </a> </td> <td> 2022.3 </td> <td> <strong>C1776</strong> </td> <td> </td> </tr> <tr> <td> <a> Parasoft C/C++test </a> </td> <td> 2022.1 </td> <td> <strong>CERT_C-CON39-a</strong> </td> <td> Do not join or detach a thread that was previously joined or detached </td> </tr> <tr> <td> <a> Polyspace Bug Finder </a> </td> <td> R2022b </td> <td> <a> CERT C: Rule CON39-C </a> </td> <td> Checks for join or detach of a joined or detached thread (rule fully covered) </td> </tr> </tbody> </table>
+
+
+## Related Vulnerabilities
+
+Search for [vulnerabilities](https://wiki.sei.cmu.edu/confluence/display/c/BB.+Definitions#BB.Definitions-vulnerability) resulting from the violation of this rule on the [CERT website](https://www.kb.cert.org/vulnotes/bymetric?searchview&query=FIELD+KEYWORDS+contains+CON39-C).
+
+## Bibliography
+
+<table> <tbody> <tr> <td> \[ <a> ISO/IEC 9899:2011 </a> \] </td> <td> Subclause 7.26.5.3, "The <code>thrd_detach</code> Function" Subclause 7.26.5.6, "The <code>thrd_join</code> Function" </td> </tr> </tbody> </table>
+
+
+## Implementation notes
+
+This query considers problematic usages of join and detach irrespective of the execution of the program and other synchronization and interprocess communication mechanisms that may be used.
+
+## References
+
+* CERT-C: [CON39-C: Do not join or detach a thread that was previously joined or detached](https://wiki.sei.cmu.edu/confluence/display/c)
diff --git a/c/cert/src/rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.ql b/c/cert/src/rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.ql
@@ -0,0 +1,50 @@
+/**
+ * @id c/cert/thread-was-previously-joined-or-detached
+ * @name CON39-C: Do not join or detach a thread that was previously joined or detached
+ * @description Joining or detaching a previously joined or detached thread can lead to undefined
+ *              program behavior.
+ * @kind problem
+ * @precision high
+ * @problem.severity error
+ * @tags external/cert/id/con39-c
+ *       correctness
+ *       concurrency
+ *       external/cert/obligation/rule
+ */
+
+import cpp
+import codingstandards.c.cert
+import codingstandards.cpp.Concurrency
+
+// OK
+// 1) Thread calls detach parent DOES NOT call join
+// 2) Parent calls join, thread does NOT call detach()
+// NOT OK
+// 1) Thread calls detach, parent calls join
+// 2) Thread calls detach twice, parent does not call join
+// 3) Parent calls join twice, thread does not call detach
+from C11ThreadCreateCall tcc
+where
+  not isExcluded(tcc, Concurrency5Package::threadWasPreviouslyJoinedOrDetachedQuery()) and
+  // Note: These cases can be simplified but they are presented like this for clarity
+  // case 1 - calls to `thrd_join` and `thrd_detach` within the parent or
+  // within the parent / child CFG.
+  exists(C11ThreadWait tw, C11ThreadDetach dt |
+    tw = getAThreadContextAwareSuccessor(tcc) and
+    dt = getAThreadContextAwareSuccessor(tcc)
+  )
+  or
+  // case 2 - multiple calls to `thrd_detach` within the threaded CFG.
+  exists(C11ThreadDetach dt1, C11ThreadDetach dt2 |
+    dt1 = getAThreadContextAwareSuccessor(tcc) and
+    dt2 = getAThreadContextAwareSuccessor(tcc) and
+    not dt1 = dt2
+  )
+  or
+  // case 3 - multiple calls to `thrd_join` within the threaded CFG.
+  exists(C11ThreadWait tw1, C11ThreadWait tw2 |
+    tw1 = getAThreadContextAwareSuccessor(tcc) and
+    tw2 = getAThreadContextAwareSuccessor(tcc) and
+    not tw1 = tw2
+  )
+select tcc, "Thread may call join or detach after the thread is joined or detached."
diff --git a/c/cert/src/rules/CON40-C/AtomicVariableTwiceInExpression.md b/c/cert/src/rules/CON40-C/AtomicVariableTwiceInExpression.md
@@ -0,0 +1,173 @@
+# CON40-C: Do not refer to an atomic variable twice in an expression
+
+This query implements the CERT-C rule CON40-C:
+
+> Do not refer to an atomic variable twice in an expression
+
+
+## Description
+
+A consistent locking policy guarantees that multiple threads cannot simultaneously access or modify shared data. Atomic variables eliminate the need for locks by guaranteeing thread safety when certain operations are performed on them. The thread-safe operations on atomic variables are specified in the C Standard, subclauses 7.17.7 and 7.17.8 \[[ISO/IEC 9899:2011](https://wiki.sei.cmu.edu/confluence/display/c/AA.+Bibliography#AA.Bibliography-ISO%2FIEC9899-2011)\]. While atomic operations can be combined, combined operations do not provide the thread safety provided by individual atomic operations.
+
+Every time an atomic variable appears on the left side of an assignment operator, including a compound assignment operator such as `*=`, an atomic write is performed on the variable. The use of the increment (++`)` or decrement `(--)` operators on an atomic variable constitutes an atomic read-and-write operation and is consequently thread-safe. Any reference of an atomic variable anywhere else in an expression indicates a distinct atomic read on the variable.
+
+If the same atomic variable appears twice in an expression, then two atomic reads, or an atomic read and an atomic write, are required. Such a pair of atomic operations is not thread-safe, as another thread can modify the atomic variable between the two operations. Consequently, an atomic variable must not be referenced twice in the same expression.
+
+## Noncompliant Code Example (atomic_bool)
+
+This noncompliant code example declares a shared `atomic_bool` `flag` variable and provides a `toggle_flag()` method that negates the current value of `flag`:
+
+```cpp
+#include <stdatomic.h>
+#include <stdbool.h>
+
+static atomic_bool flag = ATOMIC_VAR_INIT(false);
+
+void init_flag(void) {
+  atomic_init(&flag, false);
+}
+
+void toggle_flag(void) {
+  bool temp_flag = atomic_load(&flag);
+  temp_flag = !temp_flag;
+  atomic_store(&flag, temp_flag);
+}
+
+bool get_flag(void) {
+  return atomic_load(&flag);
+}
+
+```
+Execution of this code may result in unexpected behavior because the value of `flag` is read, negated, and written back. This occurs even though the read and write are both atomic.
+
+Consider, for example, two threads that call `toggle_flag()`. The expected effect of toggling `flag` twice is that it is restored to its original value. However, the scenario in the following table leaves `flag` in the incorrect state.
+
+`toggle_flag()` without Compare-and-Exchange
+
+<table> <tbody> <tr> <th> Time </th> <th> <code>flag</code> </th> <th> Thread </th> <th> Action </th> </tr> <tr> <td> 1 </td> <td> <code>true</code> </td> <td> <em> t </em> <sub> 1 </sub> </td> <td> Reads the current value of <code>flag</code> , which is <code>true,</code> into a cache </td> </tr> <tr> <td> 2 </td> <td> <code>true</code> </td> <td> <em> t </em> <sub> 2 </sub> </td> <td> Reads the current value of <code>flag</code> , which is still <code>true,</code> into a different cache </td> </tr> <tr> <td> 3 </td> <td> <code>true</code> </td> <td> <em> t </em> <sub> 1 </sub> </td> <td> Toggles the temporary variable in the cache to <code>false</code> </td> </tr> <tr> <td> 4 </td> <td> <code>true</code> </td> <td> <em> t </em> <sub> 2 </sub> </td> <td> Toggles the temporary variable in the different cache to <code>false</code> </td> </tr> <tr> <td> 5 </td> <td> <code>false</code> </td> <td> <em> t </em> <sub> 1 </sub> </td> <td> Writes the cache variable's value to <code>flag</code> </td> </tr> <tr> <td> 6 </td> <td> <code>false</code> </td> <td> <em> t </em> <sub> 2 </sub> </td> <td> Writes the different cache variable's value to <code>flag</code> </td> </tr> </tbody> </table>
+As a result, the effect of the call by *t*<sub>2</sub> is not reflected in `flag`; the program behaves as if `toggle_flag()` was called only once, not twice.
+
+
+## Compliant Solution (atomic_compare_exchange_weak())
+
+This compliant solution uses a compare-and-exchange to guarantee that the correct value is stored in `flag`. All updates are visible to other threads. The call to `atomic_compare_exchange_weak()` is in a loop in conformance with [CON41-C. Wrap functions that can fail spuriously in a loop](https://wiki.sei.cmu.edu/confluence/display/c/CON41-C.+Wrap+functions+that+can+fail+spuriously+in+a+loop).
+
+```cpp
+#include <stdatomic.h>
+#include <stdbool.h>
+
+static atomic_bool flag = ATOMIC_VAR_INIT(false);
+
+void init_flag(void) {
+  atomic_init(&flag, false);
+}
+
+void toggle_flag(void) {
+  bool old_flag = atomic_load(&flag);
+  bool new_flag;
+  do {
+    new_flag = !old_flag;
+  } while (!atomic_compare_exchange_weak(&flag, &old_flag, new_flag));
+}
+
+bool get_flag(void) {
+  return atomic_load(&flag);
+}
+```
+An alternative solution is to use the `atomic_flag` data type for managing Boolean values atomically. However, `atomic_flag` does not support a toggle operation.
+
+## Compliant Solution (Compound Assignment)
+
+This compliant solution uses the `^=` assignment operation to toggle `flag`. This operation is guaranteed to be atomic, according to the C Standard, 6.5.16.2, paragraph 3. This operation performs a bitwise-exclusive-or between its arguments, but for Boolean arguments, this is equivalent to negation.
+
+```cpp
+#include <stdatomic.h>
+#include <stdbool.h>
+
+static atomic_bool flag = ATOMIC_VAR_INIT(false);
+
+void toggle_flag(void) {
+  flag ^= 1;
+}
+
+bool get_flag(void) {
+  return flag;
+}
+```
+An alternative solution is to use a mutex to protect the atomic operation, but this solution loses the performance benefits of atomic variables.
+
+## Noncompliant Code Example
+
+This noncompliant code example takes an atomic global variable `n` and computes `n + (n - 1) + (n - 2) + ... + 1`, using the formula `n * (n + 1) / 2`:
+
+```cpp
+#include <stdatomic.h>
+
+atomic_int n = ATOMIC_VAR_INIT(0);
+
+int compute_sum(void) {
+  return n * (n + 1) / 2;
+}
+```
+The value of `n` may change between the two atomic reads of `n` in the expression, yielding an incorrect result.
+
+## Compliant Solution
+
+This compliant solution passes the atomic variable as a function argument, forcing the variable to be copied and guaranteeing a correct result. Note that the function's formal parameter need not be atomic, and the atomic variable can still be passed as an actual argument.
+
+```cpp
+#include <stdatomic.h>
+
+int compute_sum(int n) {
+  return n * (n + 1) / 2;
+}
+
+```
+
+## Risk Assessment
+
+When operations on atomic variables are assumed to be atomic, but are not atomic, surprising data races can occur, leading to corrupted data and invalid control flow.
+
+<table> <tbody> <tr> <th> Rule </th> <th> Severity </th> <th> Likelihood </th> <th> Remediation Cost </th> <th> Priority </th> <th> Level </th> </tr> <tr> <td> CON40-C </td> <td> Medium </td> <td> Probable </td> <td> Medium </td> <td> <strong>P8</strong> </td> <td> <strong>L2</strong> </td> </tr> </tbody> </table>
+
+
+## Automated Detection
+
+<table> <tbody> <tr> <th> Tool </th> <th> Version </th> <th> Checker </th> <th> Description </th> </tr> <tr> <td> <a> Astrée </a> </td> <td> 22.04 </td> <td> <strong>multiple-atomic-accesses</strong> </td> <td> Partially checked </td> </tr> <tr> <td> <a> Axivion Bauhaus Suite </a> </td> <td> 7.2.0 </td> <td> <strong>CertC-CON40</strong> </td> <td> </td> </tr> <tr> <td> <a> CodeSonar </a> </td> <td> 7.1p0 </td> <td> <strong>CONCURRENCY.MAA</strong> </td> <td> Multiple Accesses of Atomic </td> </tr> <tr> <td> <a> Coverity </a> </td> <td> 2017.07 </td> <td> <strong>EVALUATION_ORDER (partial)</strong> <strong>MISRA 2012 Rule 13.2</strong> <strong>VOLATILE_ATOICITY (possible)</strong> </td> <td> Implemented </td> </tr> <tr> <td> <a> Helix QAC </a> </td> <td> 2022.3 </td> <td> <strong>C1114, C1115, C1116</strong> <strong>C++3171, C++4150</strong> </td> <td> </td> </tr> <tr> <td> <a> Klocwork </a> </td> <td> 2022.3 </td> <td> <strong>CERT.CONC.ATOMIC_TWICE_EXPR</strong> </td> <td> </td> </tr> <tr> <td> <a> Parasoft C/C++test </a> </td> <td> 2022.1 </td> <td> <strong>CERT_C-CON40-a</strong> </td> <td> Do not refer to an atomic variable twice in an expression </td> </tr> <tr> <td> <a> Polyspace Bug Finder </a> </td> <td> R2022b </td> <td> <a> CERT C: Rule CON40-C </a> </td> <td> Checks for: Atomic variable accessed twice in an expressiontomic variable accessed twice in an expression, atomic load and store sequence not atomictomic load and store sequence not atomic. Rule fully covered. </td> </tr> <tr> <td> <a> PRQA QA-C </a> </td> <td> 9.7 </td> <td> <strong>1114, 1115, 1116 </strong> </td> <td> </td> </tr> <tr> <td> <a> RuleChecker </a> </td> <td> 22.04 </td> <td> <strong>multiple-atomic-accesses</strong> </td> <td> Partially checked </td> </tr> </tbody> </table>
+
+
+## Related Vulnerabilities
+
+Search for [vulnerabilities](https://www.securecoding.cert.org/confluence/display/seccode/BB.+Definitions#BB.Definitions-vulnerability) resulting from the violation of this rule on the [CERT website](https://www.kb.cert.org/vulnotes/bymetric?searchview&query=FIELD+KEYWORDS+contains+CON40-C).
+
+## Related Guidelines
+
+[Key here](https://wiki.sei.cmu.edu/confluence/display/c/How+this+Coding+Standard+is+Organized#HowthisCodingStandardisOrganized-RelatedGuidelines) (explains table format and definitions)
+
+<table> <tbody> <tr> <th> Taxonomy </th> <th> Taxonomy item </th> <th> Relationship </th> </tr> <tr> <td> <a> CWE 2.11 </a> </td> <td> <a> CWE-366 </a> , Race Condition within a Thread </td> <td> 2017-07-07: CERT: Rule subset of CWE </td> </tr> </tbody> </table>
+
+
+## CERT-CWE Mapping Notes
+
+[Key here](https://wiki.sei.cmu.edu/confluence/pages/viewpage.action?pageId=87152408#HowthisCodingStandardisOrganized-CERT-CWEMappingNotes) for mapping notes
+
+**CWE-366 and CON40-C**
+
+CON40-C = Subset( CON43-C) Intersection( CON32-C, CON40-C) = Ø
+
+CWE-366 = Union( CON40-C, list) where list =
+
+* C data races that do not involve an atomic variable used twice within an expression
+
+## Bibliography
+
+<table> <tbody> <tr> <td> \[ <a> ISO/IEC 9899:2011 </a> \] </td> <td> 6.5.16.2, "Compound Assignment" 7.17, "Atomics" </td> </tr> </tbody> </table>
+
+
+## Implementation notes
+
+None
+
+## References
+
+* CERT-C: [CON40-C: Do not refer to an atomic variable twice in an expression](https://wiki.sei.cmu.edu/confluence/display/c)
diff --git a/c/cert/src/rules/CON40-C/AtomicVariableTwiceInExpression.ql b/c/cert/src/rules/CON40-C/AtomicVariableTwiceInExpression.ql
@@ -0,0 +1,47 @@
+/**
+ * @id c/cert/atomic-variable-twice-in-expression
+ * @name CON40-C: Do not refer to an atomic variable twice in an expression
+ * @description Atomic variables that are referred to twice in the same expression can produce
+ *              unpredictable program behavior.
+ * @kind problem
+ * @precision very-high
+ * @problem.severity error
+ * @tags external/cert/id/con40-c
+ *       correctness
+ *       concurrency
+ *       external/cert/obligation/rule
+ */
+
+import cpp
+import codingstandards.c.cert
+
+from MacroInvocation mi, Variable v, Locatable whereFound
+where
+  not isExcluded(whereFound, Concurrency5Package::atomicVariableTwiceInExpressionQuery()) and
+  (
+    // There isn't a way to safely use this construct in a way that is also
+    // possible the reliably detect so advise against using it.
+    (
+      mi.getMacroName() = ["atomic_store", "atomic_store_explicit"]
+      or
+      // This construct is generally safe, but must be used in a loop. To lower
+      // the false positive rate we don't look at the conditions of the loop and
+      // instead assume if it is found in a looping construct that it is likely
+      // related to the safety property.
+      mi.getMacroName() = ["atomic_compare_exchange_weak", "atomic_compare_exchange_weak_explicit"] and
+      not exists(Loop l | mi.getAGeneratedElement().(Expr).getParent*() = l)
+    ) and
+    whereFound = mi
+  )
+  or
+  mi.getMacroName() = "ATOMIC_VAR_INIT" and
+  exists(Expr av |
+    av = mi.getAGeneratedElement() and
+    av = v.getAnAssignedValue() and
+    exists(Assignment m |
+      not m instanceof AssignXorExpr and
+      m.getLValue().(VariableAccess).getTarget() = v and
+      whereFound = m
+    )
+  )
+select mi, "Atomic variable possibly referred to twice in an $@.", whereFound, "expression"
diff --git a/c/cert/test/rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.expected b/c/cert/test/rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.expected
@@ -0,0 +1,8 @@
+| test.c:26:3:26:13 | call to thrd_create | Thread may call join or detach after the thread is joined or detached. |
+| test.c:32:3:32:13 | call to thrd_create | Thread may call join or detach after the thread is joined or detached. |
+| test.c:37:3:37:13 | call to thrd_create | Thread may call join or detach after the thread is joined or detached. |
+| test.c:58:3:58:13 | call to thrd_create | Thread may call join or detach after the thread is joined or detached. |
+| test.c:66:3:66:13 | call to thrd_create | Thread may call join or detach after the thread is joined or detached. |
+| test.c:73:3:73:13 | call to thrd_create | Thread may call join or detach after the thread is joined or detached. |
+| test.c:87:3:87:13 | call to thrd_create | Thread may call join or detach after the thread is joined or detached. |
+| test.c:94:3:94:13 | call to thrd_create | Thread may call join or detach after the thread is joined or detached. |
diff --git a/c/cert/test/rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.qlref b/c/cert/test/rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.qlref
@@ -0,0 +1 @@
+rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.ql
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		rules/CON39-C/ThreadWasPreviouslyJoinedOrDetached.ql