Re: [RFC PATCH for 4.18 1/2] rseq: validate rseq_cs fields are < TASK_SIZE

On Mon, Jul 2, 2018 at 12:00 PM, Mathieu Desnoyers
[off-list ref] wrote:

----- On Jul 2, 2018, at 1:11 PM, Andy Lutomirski luto@amacapital.net wrote:

quoted

But I think that the limited solution of changing
instruction_pointer_set() really is a sufficient
architecture-dependent change to fully solve your problem.

So let me recap with the changes I gather for 4.18 and 4.19:

4.18:

* Change struct rseq_cs field types from LINUX_FIELD_u32_u64() to __u64 in
  uapi/linux/rseq.h,
* Compare rseq->rseq_cs->abort_ip with TASK_SIZE before using it. Kill offending
  process if its value is over TASK_SIZE,
* Explicitly check that padding of rseq->rseq_cs is zero on 32-bit kernels
  (#ifndef __LP64__).

4.19:

* Introduce instruction_pointer_set() with input validation, use it when setting
  IP to abort_ip in rseq. This replaces the comparison of abort_ip with TASK_SIZE.

Is that consistent with what you have in mind ?

Works for me.  Linus, any objection?