python accessing freed shared memory object (#1253)

* added a 'isValid' member in shared memory (also updated shm version) with default true, any access to shared memory() checks also for validity. any free will set this to false and then unmap shm. Any access to shm will then check validity in python.

* fixed tests for shm

* added tests in python as well

---------

Co-authored-by: Alice <alice.mazzoleni@psi.ch>

slsDetectorSoftware/src/CtbConfig.h

@@ -56,6 +56,7 @@ class CtbConfig {
     std::string getSlowADCName(size_t index) const;
     std::vector<std::string> getSlowADCNames() const;
     static const char *shm_tag();
+    bool isValid{true}; // false if freed to block access from python or c++ api
 };
 
 } // namespace sls

slsDetectorSoftware/src/Detector.cpp

@@ -29,6 +29,8 @@ void freeSharedMemory(const int detectorIndex, const int moduleIndex) {
     if (moduleIndex >= 0) {
         SharedMemory<sharedModule> moduleShm(detectorIndex, moduleIndex);
         if (moduleShm.exists()) {
+            moduleShm.openSharedMemory(false);
+            moduleShm()->isValid = false;
             moduleShm.removeSharedMemory();
         }
         return;
@@ -41,18 +43,26 @@ void freeSharedMemory(const int detectorIndex, const int moduleIndex) {
     if (detectorShm.exists()) {
         detectorShm.openSharedMemory(false);
         numDetectors = detectorShm()->totalNumberOfModules;
+        detectorShm()->isValid = false;
         detectorShm.removeSharedMemory();
     }
 
     for (int i = 0; i < numDetectors; ++i) {
         SharedMemory<sharedModule> moduleShm(detectorIndex, i);
+        if (moduleShm.exists()) {
+            moduleShm.openSharedMemory(false);
+            moduleShm()->isValid = false;
+        }
         moduleShm.removeSharedMemory();
     }
 
     // Ctb configuration
     SharedMemory<CtbConfig> ctbShm(detectorIndex, -1, CtbConfig::shm_tag());
-    if (ctbShm.exists())
+    if (ctbShm.exists()) {
+        ctbShm.openSharedMemory(false);
+        ctbShm()->isValid = false;
         ctbShm.removeSharedMemory();
+    }
 }
 
 using defs = slsDetectorDefs;

slsDetectorSoftware/src/DetectorImpl.h

@@ -24,7 +24,7 @@ class detectorData;
 class Module;
 
 #define DETECTOR_SHMAPIVERSION 0x190809
-#define DETECTOR_SHMVERSION    0x250616
+#define DETECTOR_SHMVERSION    0x250729
 #define SHORT_STRING_LENGTH    50
 
 /**
@@ -51,6 +51,8 @@ struct sharedDetector {
     int totalNumberOfModules;
     slsDetectorDefs::detectorType detType;
 
+    bool isValid{true}; // false if freed to block access from python or c++ api
+
     /** END OF FIXED PATTERN
      * -----------------------------------------------*/
 

slsDetectorSoftware/src/Module.h

@@ -19,7 +19,7 @@ namespace sls {
 class ServerInterface;
 
 #define MODULE_SHMAPIVERSION 0x190726
-#define MODULE_SHMVERSION    0x230913
+#define MODULE_SHMVERSION    0x250729
 
 /**
  * @short structure allocated in shared memory to store Module settings for
@@ -32,6 +32,7 @@ struct sharedModule {
     int shmversion;
     char hostname[MAX_STR_LENGTH];
     slsDetectorDefs::detectorType detType;
+    bool isValid{true}; // false if freed to block access from python or c++ api
 
     /** END OF FIXED PATTERN -----------------------------------------------*/
 

slsDetectorSoftware/src/SharedMemory.h

@@ -10,6 +10,7 @@
  *@short functions basic implemenation of shared memory
  */
 
+#include "sls/TypeTraits.h"
 #include "sls/logger.h"
 #include "sls/sls_detector_exceptions.h"
 
@@ -26,11 +27,18 @@
 
 namespace sls {
 
+struct sharedDetector;
+
 #define SHM_DETECTOR_PREFIX "/slsDetectorPackage_detector_"
 #define SHM_MODULE_PREFIX   "_module_"
 #define SHM_ENV_NAME        "SLSDETNAME"
 
 template <typename T> class SharedMemory {
+
+    static_assert(has_bool_isValid<T>::value,
+                  "SharedMemory requires the struct to have a bool member "
+                  "named 'isValid'");
+
     static constexpr int NAME_MAX_LENGTH = 255;
     std::string name;
     T *shared_struct{nullptr};
@@ -65,15 +73,21 @@ template <typename T> class SharedMemory {
     }
 
     T *operator()() {
-        if (shared_struct)
-            return shared_struct;
-        throw SharedMemoryError(getNoShmAccessMessage());
+        if (!shared_struct)
+            throw SharedMemoryError(getNoShmAccessMessage());
+        if (!shared_struct->isValid) {
+            throw SharedMemoryError(getInvalidShmMessage());
+        }
+        return shared_struct;
     }
 
     const T *operator()() const {
-        if (shared_struct)
-            return shared_struct;
-        throw SharedMemoryError(getNoShmAccessMessage());
+        if (!shared_struct)
+            throw SharedMemoryError(getNoShmAccessMessage());
+        if (!shared_struct->isValid) {
+            throw SharedMemoryError(getInvalidShmMessage());
+        }
+        return shared_struct;
     }
 
     std::string getName() const { return name; }
@@ -215,10 +229,15 @@ template <typename T> class SharedMemory {
         }
     }
 
-    const char *getNoShmAccessMessage() const {
+    inline const char *getNoShmAccessMessage() const {
         return ("No shared memory to access. Create it first with "
                 "hostname or config command.");
     };
+
+    inline const char *getInvalidShmMessage() const {
+        return ("Shared memory is invalid or freed. Close resources before "
+                "access.");
+    };
 };
 
 } // namespace sls