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Date: Thu, 10 Jan 2019 10:14:24 +0100
From: Adam Borowski <kilobyte@angband.pl>
Subject: Re: [PATCH] mm/mmu_notifier: mm/rmap.c: Fix a mmu_notifier range bug
 in try_to_unmap_one
Message-ID: <20190110091424.mzgpdaqq74ie6ro5@angband.pl>
References: <20190110005117.18282-1-sean.j.christopherson@intel.com>
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In-Reply-To: <20190110005117.18282-1-sean.j.christopherson@intel.com>
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To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, leozinho29_eu@hotmail.com, Mike Galbraith <efault@gmx.de>, =?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>, Christian =?iso-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>, Jan Kara <jack@suse.cz>, Matthew Wilcox <mawilcox@microsoft.com>, Ross Zwisler <zwisler@kernel.org>, Dan Williams <dan.j.williams@intel.com>, Paolo Bonzini <pbonzini@redhat.com>, Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>, Michal Hocko <mhocko@kernel.org>, Felix Kuehling <felix.kuehling@amd.com>, Ralph Campbell <rcampbell@nvidia.com>, John Hubbard <jhubbard@nvidia.com>, Andrew Morton <akpm@linux-foundation.org>, Linus Torvalds <torvalds@linux-foundation.org>

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@angband.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?