Fix mlock/mlock2/munlock in case of zero length.

Author: pizlonator

filc/tests/mlocknull/manifest

@@ -0,0 +1,4 @@
+return:
+  failure
+output-includes:
+  - "cannot read pointer with null object"

filc/tests/mlocknull/mlocknull.c

@@ -0,0 +1,8 @@
+#include <errno.h>
+#include <stdio.h>
+#include <sys/mman.h>
+int main(void) {
+  if (mlock(NULL, 4096) == -1)
+    perror("mlock");
+  return 0;
+}

filc/tests/mlockzerobytes/manifest

@@ -0,0 +1,2 @@
+return:
+  success

filc/tests/mlockzerobytes/mlockzerobytes.c

@@ -0,0 +1,24 @@
+#include <errno.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <stdfil.h>
+#include <string.h>
+int main(void) {
+    ZASSERT(!mlock(NULL, 0));
+    ZASSERT(!mlock(main, 0));
+    int res = mlock((void*)666, 0);
+    int my_errno = errno;
+    zprintf("res = %d, error = %s\n", res, strerror(my_errno));
+    ZASSERT(res == -1);
+    ZASSERT(my_errno == ENOMEM);
+    ZASSERT(!mlock(zweak_new(NULL), 0));
+    ZASSERT(!munlock(NULL, 0));
+    ZASSERT(!munlock(main, 0));
+    res = munlock((void*)666, 0);
+    my_errno = errno;
+    zprintf("res = %d, error = %s\n", res, strerror(my_errno));
+    ZASSERT(res == -1);
+    ZASSERT(my_errno == ENOMEM);
+    ZASSERT(!munlock(zweak_new(NULL), 0));
+    return 0;
+}

libpas/src/libpas/filc_runtime.c

@@ -8950,8 +8950,12 @@ int filc_native_zsys_getsid(filc_thread* my_thread, int pid)
 static int mlock_impl(filc_thread* my_thread, filc_ptr addr_ptr, size_t len,
                       int (*actual_mlock)(const void*, size_t))
 {
-    filc_check_access(addr_ptr, len, filc_read_access);
-    check_mmap(addr_ptr);
+    /* Only check the pointer if len is not zero. If len is zero, still make the syscall, because I am
+       guessing someone might do this to check capabilities. */
+    if (len) {
+        filc_check_access(addr_ptr, len, filc_read_access);
+        check_mmap(addr_ptr);
+    }
     return FILC_SYSCALL(my_thread, actual_mlock(filc_ptr_ptr(addr_ptr), len));
 }