linux-kernel - Re: [PATCH] mm/mmu_notifier: mm/rmap.c: Fix a mmu_notifier range bug in try_to_unmap

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Date:   Thu, 10 Jan 2019 10:14:24 +0100
From:   Adam Borowski <kilobyte@...band.pl>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        leozinho29_eu@...mail.com, Mike Galbraith <efault@....de>,
        Jérôme Glisse <jglisse@...hat.com>,
        Christian König <christian.koenig@....com>,
        Jan Kara <jack@...e.cz>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Ross Zwisler <zwisler@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Felix Kuehling <felix.kuehling@....com>,
        Ralph Campbell <rcampbell@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] mm/mmu_notifier: mm/rmap.c: Fix a mmu_notifier range bug
 in try_to_unmap_one

On Wed, Jan 09, 2019 at 04:51:17PM -0800, Sean Christopherson wrote:
> Manifests as KVM use-after-free WARNINGs and subsequent "BUG: Bad page
> state in process X" errors when reclaiming from a KVM guest due to KVM
> removing the wrong pages from its own mappings.

With your patch, no badness happened so far.  Thanks!

> Reported-by: Adam Borowski <kilobyte@...band.pl>
> Fixes: ac46d4f3c432 ("mm/mmu_notifier: use structure for invalidate_range_start/end calls v2")

> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> -	mmu_notifier_range_init(&range, vma->vm_mm, vma->vm_start,
> -				min(vma->vm_end, vma->vm_start +
> +	mmu_notifier_range_init(&range, vma->vm_mm, address,
> +				min(vma->vm_end, address +


Meow.
-- 
⢀⣴⠾⠻⢶⣦⠀ Hans 1 was born and raised in Johannesburg, then moved to Boston,
⣾⠁⢠⠒⠀⣿⡁ and has just became a naturalized citizen.  Hans 2's grandparents
⢿⡄⠘⠷⠚⠋⠀ came from Melanesia to Düsseldorf, and he hasn't ever been outside
⠈⠳⣄⠀⠀⠀⠀ Germany until yesterday.  Which one is an African-American?