linux-kernel - Re: [PATCH 4.4 037/107] x86/mm: Factor out LDT init from context init

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Date:   Sat, 25 Aug 2018 00:44:10 +0100
From:   Ben Hutchings <ben.hutchings@...ethink.co.uk>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>, Dave Hansen <dave@...1.net>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
        Ingo Molnar <mingo@...nel.org>,
        "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>,
        "Matt Helsley (VMware)" <matt.helsley@...il.com>,
        Alexey Makhalov <amakhalov@...are.com>,
        Bo Gan <ganb@...are.com>
Subject: Re: [PATCH 4.4 037/107] x86/mm: Factor out LDT init from context
 init

On Mon, 2018-07-23 at 14:41 +0200, Greg Kroah-Hartman wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Dave Hansen <dave.hansen@...ux.intel.com>
> 
> commit 39a0526fb3f7d93433d146304278477eb463f8af upstream
[...]
> --- a/arch/x86/include/asm/mmu_context.h
> +++ b/arch/x86/include/asm/mmu_context.h
[...]
> +static inline int init_new_context(struct task_struct *tsk,
> +				   struct mm_struct *mm)
> +{
> +	init_new_context_ldt(tsk, mm);
> +	return 0;
> +}
[...]

This hides errors from init_new_context_ldt(), which is very bad.
Fixed upstream by:

commit ccd5b3235180eef3cfec337df1c8554ab151b5cc
Author: Eric Biggers <ebiggers@...gle.com>
Date:   Thu Aug 24 10:50:29 2017 -0700

    x86/mm: Fix use-after-free of ldt_struct

Ben.

-- 
Ben Hutchings, Software Developer                         Codethink Ltd
https://www.codethink.co.uk/                 Dale House, 35 Dale Street
                                     Manchester, M1 2HF, United Kingdom