Return NULL for mmap fail case on Unix (#78069)

* Return NULL for mmap fail case on Unix

If mmap failed, "MAP_FAILED" is returned not "NULL".
The windows implememtation of GetRWMapping returns "NULL" for fail case,
and the caller function is also checking "NULL".

So, change Unix implementation to return "NULL" for fail case.

* call memset when mmap succeeds

* check MAP_FAILED instead of NULL

* return false for failing mmap

* Call g_fatalErrorHandler if releasing failed

* Update src/coreclr/utilcode/executableallocator.cpp

Co-authored-by: Jan Vorlicek <jan.vorlicek@volny.cz>

* Fix wrong condition check

Co-authored-by: Jan Vorlicek <jan.vorlicek@volny.cz>

1 files changed, 10 insertions, 2 deletions

diff --git a/src/coreclr/minipal/Unix/doublemapping.cpp b/src/coreclr/minipal/Unix/doublemapping.cpp
index 57ce0c09f28..cb65e5e284e 100644
--- a/src/coreclr/minipal/Unix/doublemapping.cpp
+++ b/src/coreclr/minipal/Unix/doublemapping.cpp
@@ -198,7 +198,10 @@ bool VMToOSInterface::ReleaseDoubleMappedMemory(void *mapperHandle, void* pStart
 {
 #ifndef TARGET_OSX
     int fd = (int)(size_t)mapperHandle;
-    mmap(pStart, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd, offset);
+    if (mmap(pStart, size, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_FIXED, fd, offset) == MAP_FAILED)
+    {
+        return false;
+    }
     memset(pStart, 0, size);
 #endif // TARGET_OSX
     return munmap(pStart, size) != -1;
@@ -208,7 +211,12 @@ void* VMToOSInterface::GetRWMapping(void *mapperHandle, void* pStart, size_t off
 {
 #ifndef TARGET_OSX
     int fd = (int)(size_t)mapperHandle;
-    return mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
+    void* result = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
+    if (result == MAP_FAILED)
+    {
+        result = NULL;
+    }
+    return result;
 #else // TARGET_OSX
 #ifdef TARGET_AMD64
     vm_address_t startRW;