Secure pointers

• US 20040193814A1
• Filed: 03/27/2003
• Published: 09/30/2004
• Est. Priority Date: 03/27/2003
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: McCarthy, Patrick J., Erickson, Kevin J., Plaetzer, Scott A., Kirkman, Richard K.
• Granted Patent: US 7,181,580 B2
• Time in Patent Office: Days
• US Class Current: 711/156
• CPC Class Codes: G06F 12/1458 by checking the subject access rights
• CPC Class Codes: G06F 21/52 during program execution, e.g. stack integrity ; Preventing unwanted data erasure; Buffer overflow
• CPC Class Codes: G06F 2221/2105 Dual mode as a secondary aspect

Abstract

A method, apparatus, system, and signal-bearing medium that in an embodiment map a pointer to a target indirectly via a pointer map. In an embodiment, the pointer map is stored in a reserved area and an entry for the pointer in the pointer map includes a back-pointer containing an address of the pointer and a target-address containing the address of the target. When the pointer is accessed, the pointer is checked to ensure its contents point at the entry in the pointer map in the reserved area and that the back-pointer in the pointer map entry points back at the pointer. In this way, pointers are protected from being modified illegitimately.

Claims

1. A method comprising:

mapping a pointer to a target indirectly via a pointer map.

2. The method of claim 1, wherein the pointer points at an entry in the pointer map, the entry points at the target, and the entry points back at the pointer.

3. The method of claim 2, wherein the mapping further comprises:

receiving an address of the pointer;

finding the entry based on contents located at the address of the pointer; and

verifying that the entry points back at the pointer.

4. The method of claim 2, wherein the mapping further comprises:

verifying that the entry is located within a reserved address range.

5. The method of claim 2, wherein the mapping further comprises:

receiving an address of the target; and

storing the address of the target in a target-pointer field in the entry.

6. The method of claim 2, wherein the mapping further comprises:

receiving an address of the pointer; and

storing the address of the pointer in a back-pointer field in the entry.

7. The method of claim 2, wherein the mapping further comprises:

receiving an address of the pointer; and

storing an address of the entry at a location indicated by the address of the pointer.

8. An apparatus comprising:

means for storing a target-address in an entry of a pointer-map;

means for storing a pointer-address in the entry of the pointer-map; and

means for storing an address of the entry in a location indicated by the pointer-address.

9. The apparatus of claim 8, further comprising:

means for storing control information in the entry of the pointer-map.

10. The apparatus of claim 9, wherein the control information is selected from a group consisting of:

a context, a process, a local/global scope, and a profile.

11. The apparatus of claim 9, further comprising:

means for verifying that a process associated with the pointer-address has attributes that satisfy the control information.

12. The apparatus of claim 8, further comprising:

means for determining whether a pointer is valid based on the pointer-address.

13. A signal-bearing medium encoded with instructions, wherein the instructions when executed comprise:

receiving a pointer-address and a target-address;

determining whether a pointer has a valid entry in a pointer map based on the pointer-address;

when the valid entry does not exist, creating a new entry in the pointer map for the pointer; and

storing the target-address in the new entry.

14. The signal-bearing medium of claim 13, wherein the instructions further comprise:

storing the pointer-address in the new entry.

15. The signal-bearing medium of claim 13, wherein the instructions further comprise:

storing control information in the new entry.

16. The signal-bearing medium of claim 15, wherein the control information is selected from a group consisting of:

context, process, local/global scope, and profile.

17. The signal-bearing medium of claim 13, wherein the determining further comprises:

verifying whether content at the pointer-address comprises an address within a reserved range.

18. A signal-bearing medium encoded with a data structure accessed by a controller that is to be executed by a processor, wherein the data structure comprises at least one entry, wherein the entry comprises:

a back-pointer, wherein the controller is to set an address of a pointer in the back-pointer; and

a target-address, wherein the controller is to set an address of a target of the pointer in the target-address.

19. The signal-bearing medium of claim 18, where the at least one entry further comprises:

control information, wherein the pointer controller is further to set the control information.

20. The signal-bearing medium of claim 18, wherein the controller is further to:

store an address of the entry at a location indicated by the address of the pointer.

21. The signal-bearing medium of claim 18, wherein the controller is further to:

receive the address of the pointer; and

determine whether the entry is valid based on content at a location indicated by the address of the pointer.

22. The signal-bearing medium of claim 18, wherein the controller is further to:

receive the address of the pointer;

find the entry based on the address of the pointer;

find the address of the target based on the entry; and

return the address of the target.

23. An electronic device comprising:

a processor; and

a storage device encoded with instructions, wherein the instructions when executed on the processor comprise;

receiving a pointer-address and a target-address,

determining whether a pointer has an entry that is valid in a pointer map based on the pointer-address,

when the pointer has the entry that is valid, storing the target-address in the valid entry.

24. The electronic device of claim 23, wherein the instructions further comprise:

storing the pointer-address in the valid entry.

25. The electronic device of claim 23, wherein the determining further comprises:

verifying whether content at the pointer-address comprises an address of the entry within a reserved range.

26. The electronic device of claim 23, wherein the determining further comprises:

verifying whether a back-pointer in the entry points at the pointer-address.