linux-kernel - Re: [RFC PATCH] mm, oom: distinguish blockable mode for mmu notifiers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d617fc1d-28a7-3441-7465-bedf4dc69976@redhat.com>
Date:   Sun, 24 Jun 2018 10:11:21 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Michal Hocko <mhocko@...e.com>, kvm@...r.kernel.org,
        Radim Krčmář <rkrcmar@...hat.com>,
        linux-mm@...ck.org, Andrea Arcangeli <aarcange@...hat.com>,
        Jérôme Glisse <jglisse@...hat.com>
Subject: Re: [RFC PATCH] mm, oom: distinguish blockable mode for mmu notifiers

On 22/06/2018 17:02, Michal Hocko wrote:
> @@ -7215,6 +7216,8 @@ void kvm_arch_mmu_notifier_invalidate_range(struct kvm *kvm,
>  	apic_address = gfn_to_hva(kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
>  	if (start <= apic_address && apic_address < end)
>  		kvm_make_all_cpus_request(kvm, KVM_REQ_APIC_PAGE_RELOAD);
> +
> +	return 0;

This is wrong, gfn_to_hva can sleep.

You could do the the kvm_make_all_cpus_request unconditionally, but only
if !blockable is a really rare thing.  OOM would be fine, since the
request actually would never be processed, but I'm afraid of more uses
of !blockable being introduced later.

Thanks,

Paolo