From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [RFC PATCH for 4.18 1/2] rseq: validate rseq_cs fields are <
 TASK_SIZE
Date: Mon, 2 Jul 2018 15:00:15 -0400 (EDT)
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To: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Andy Lutomirski <luto@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, linux-kernel <linux-kernel@vger.kernel.org>, linux-api <linux-api@vger.kernel.org>, Peter Zijlstra <peterz@infradead.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Boqun Feng <boqun.feng@gmail.com>, Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>, Andrew Morton <akpm@linux-foundation.org>, Russell King <linux@arm.linux.org.uk>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>, Ben Maurer <bmaurer@fb.com>, rostedt <rostedt@goodmis.org>, Josh Triplett <josh@joshtriplett.org>, Catalin Marinas <catalin.marinas@arm.com>Will Deacon <w>
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----- On Jul 2, 2018, at 1:11 PM, Andy Lutomirski luto@amacapital.net 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 ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com