linux-kernel - [PATCH 0/3] KVM: x86 SRCU bug fix and SRCU hardening

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Message-Id: <20220415004343.2203171-1-seanjc@google.com>
Date:   Fri, 15 Apr 2022 00:43:40 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Atish Patra <atishp@...shpatra.org>,
        David Hildenbrand <david@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, linuxppc-dev@...ts.ozlabs.org,
        kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 0/3] KVM: x86 SRCU bug fix and SRCU hardening

Fix an x86 bug where KVM overwrites vcpu->srcu_idx and can leak an SRCU
lock due to unlocking the wrong index, ultimately causing a hang if/when
KVM attempts to synchronize.

Switch RISC-V to the generic vcpu->srcu_idx, for reasons unknown it has
its own copy and ignores the generic one.

Add helpers with rudimentary detection of illegal vcpu->srcu_idx usage,
the x86 bug would have been incredibly painful to debug had I not known
what to look for (found by a selftest with very specific behavior...
that we recently modified with respect to SRCU).

Non-x86 changes are compile tested only.

Sean Christopherson (3):
  KVM: x86: Don't re-acquire SRCU lock in complete_emulated_io()
  KVM: RISC-V: Use kvm_vcpu.srcu_idx, drop RISC-V's unnecessary copy
  KVM: Add helpers to wrap vcpu->srcu_idx and yell if it's abused

 arch/powerpc/kvm/book3s_64_mmu_radix.c |  9 ++++---
 arch/powerpc/kvm/book3s_hv_nested.c    | 16 ++++++------
 arch/powerpc/kvm/book3s_rtas.c         |  4 +--
 arch/powerpc/kvm/powerpc.c             |  4 +--
 arch/riscv/include/asm/kvm_host.h      |  3 ---
 arch/riscv/kvm/vcpu.c                  | 16 ++++++------
 arch/riscv/kvm/vcpu_exit.c             |  4 +--
 arch/s390/kvm/interrupt.c              |  4 +--
 arch/s390/kvm/kvm-s390.c               |  8 +++---
 arch/s390/kvm/vsie.c                   |  4 +--
 arch/x86/kvm/x86.c                     | 35 +++++++++++---------------
 include/linux/kvm_host.h               | 24 +++++++++++++++++-
 12 files changed, 72 insertions(+), 59 deletions(-)


base-commit: 150866cd0ec871c765181d145aa0912628289c8a
-- 
2.36.0.rc0.470.gd361397f0d-goog