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

[Andy Lutomirski]

On Mon, Jul 2, 2018 at 12:00 PM, Mathieu Desnoyers
<mathieu.desnoyers@xxxxxxxxxxxx> wrote:
> ----- On Jul 2, 2018, at 1:11 PM, Andy Lutomirski luto@xxxxxxxxxxxxxx wrote:
>>
>> 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?