Exploit Methods/Userspace data usage
Details
Sometimes an attacker won't be able to control the instruction pointer directly, but they will be able to redirect the dereference a structure or other pointer. In these cases, it is easiest to aim at malicious structures that have been built in userspace to perform the exploitation.
Note that this is a superset that includes Userspace execution. If we can protect against userspace access, we'll also be protecting against userspace execution.
Examples
Mitigations
- hardware segmentation: SMAP (x86), PAN (arm, arm64), Domains (arm)
- emulated PAN (memory segmentation via segments, Domains, page table swapping, PCID, etc. e.g. PAX_MEMORY_UDEREF)
Right now, the upstream options available for Privileged Access Never (PAN) are:
| CPU | Feature Name | |
|---|---|---|
| ARM | v7 32-bit non-LPAE | CONFIG_CPU_SW_DOMAIN_PAN |
| v7 32-bit LPAE | CONFIG_CPU_TTBR0_PAN (Catalin's series) | |
| v8.0 32-bit | CONFIG_CPU_TTBR0_PAN | |
| v8.0 64-bit | nothing | |
| v8.1 | hardware PAN | |
| x86 | pre-late-Broadwell | nothing |
| Broadwell+ | hardware PAN (SMAP) | |
| s/390 | hardware PAN (architectural?) | |
| powerpc | nothing? | |
| MIPS | nothing? | |