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From:   Andy Lutomirski <luto@amacapital.net>
Date:   Mon, 2 Jul 2018 12:02:18 -0700
Message-ID: <CALCETrVMhU8SrZBXOXxJerrZpQ71A_f_cRBCU=Lmj_KPV0+rRA@mail.gmail.com>
Subject: Re: [RFC PATCH for 4.18 1/2] rseq: validate rseq_cs fields are < TASK_SIZE
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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 <will.deacon@arm.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Joel Fernandes <joelaf@google.com>
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On Mon, Jul 2, 2018 at 12:00 PM, Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
> ----- 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 ?
>

Works for me.  Linus, any objection?