linux-kernel - Re: [PATCH 01/10] KVM: x86: Don't take kvm->lock when iterating over vCPUs in suspend notifier

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: <5cc5a8ef-b405-44f8-b799-ec9db39ac695@xen.org>
Date: Tue, 21 Jan 2025 16:01:33 +0000
From: Paul Durrant <xadimgnik@...il.com>
To: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>, David Woodhouse <dwmw2@...radead.org>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzbot+352e553a86e0d75f5120@...kaller.appspotmail.com,
 Paul Durrant <pdurrant@...zon.com>, David Woodhouse <dwmw@...zon.co.uk>,
 Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH 01/10] KVM: x86: Don't take kvm->lock when iterating over
 vCPUs in suspend notifier

On 18/01/2025 00:55, Sean Christopherson wrote:
> When queueing vCPU PVCLOCK updates in response to SUSPEND or HIBERNATE,
> don't take kvm->lock as doing so can trigger a largely theoretical
> deadlock, it is perfectly safe to iterate over the xarray of vCPUs without
> holding kvm->lock, and kvm->lock doesn't protect kvm_set_guest_paused() in
> any way (pv_time.active and pvclock_set_guest_stopped_request are
> protected by vcpu->mutex, not kvm->lock).
> 
> Reported-by: syzbot+352e553a86e0d75f5120@...kaller.appspotmail.com
> Closes: https://lore.kernel.org/all/677c0f36.050a0220.3b3668.0014.GAE@google.com
> Fixes: 7d62874f69d7 ("kvm: x86: implement KVM PM-notifier")
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Paul Durrant <paul@....org>