linux:sockstat plugin and list_sockets API: improve pointers validation

volatility3/framework/plugins/linux/sockstat.py

@@ -438,7 +438,7 @@ class Sockstat(plugins.PluginInterface):
     """Lists all network connections for all processes."""
 
     _required_framework_version = (2, 0, 0)
-    _version = (3, 0, 2)
+    _version = (3, 0, 3)
 
     @classmethod
     def get_requirements(cls):
@@ -514,25 +514,28 @@ class Sockstat(plugins.PluginInterface):
             fd_num, filp, _full_path = fd_internal.fd_fields
             task = fd_internal.task
 
+            if not (filp.f_op and filp.f_op.is_readable()):
+                continue
+
             if filp.f_op not in (sfop_addr, dfop_addr):
                 continue
 
             dentry = filp.get_dentry()
-            if not dentry:
+            if not (dentry and dentry.is_readable()):
                 continue
 
             d_inode = dentry.d_inode
-            if not d_inode:
+            if not (d_inode and d_inode.is_readable()):
                 continue
 
             socket_alloc = linux.LinuxUtilities.container_of(
                 d_inode, "socket_alloc", "vfs_inode", vmlinux
             )
-            socket = socket_alloc.socket
-
-            if not (socket and socket.sk):
+            if not socket_alloc:
+                continue
+            socket = socket_alloc.socket
+            if not (socket.sk and socket.sk.is_readable()):
                 continue
-
             sock = socket.sk.dereference()
 
             sock_type = sock.get_type()