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

Sean Christopherson
2022-04-15T00:43:51Z

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
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2.36.0.rc0.470.gd361397f0d-goog