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[PW_SID:1100131] [v2] RISC-V: KVM: Document a TOCTOU race in SBI system suspend handler #2005

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[PW_SID:1100131] [v2] RISC-V: KVM: Document a TOCTOU race in SBI system suspend handler #2005

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14 changes: 14 additions & 0 deletions arch/riscv/kvm/vcpu_sbi_system.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,20 @@ static int kvm_sbi_ext_susp_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
return 0;
}

/*
* Check that all other vCPUs are stopped before entering
* system suspend.
*
* There is a known TOCTOU race here: a concurrent HSM
* HART_START on another vCPU can start a vCPU after it
* has already passed this check, violating the invariant.
*
* We do not fix this because:
* 1. Triggering the race requires a pathological guest.
* 2. Only guest state is at risk, not host integrity.
* 3. Userspace can double-check vCPU states before
* proceeding with suspend.
*/
kvm_for_each_vcpu(i, tmp, vcpu->kvm) {
if (tmp == vcpu)
continue;
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