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Message-Id: <20240821153844.60084-24-steven.price@arm.com>
Date: Wed, 21 Aug 2024 16:38:24 +0100
From: Steven Price <steven.price@....com>
To: kvm@...r.kernel.org,
kvmarm@...ts.linux.dev
Cc: Steven Price <steven.price@....com>,
Catalin Marinas <catalin.marinas@....com>,
Marc Zyngier <maz@...nel.org>,
Will Deacon <will@...nel.org>,
James Morse <james.morse@....com>,
Oliver Upton <oliver.upton@...ux.dev>,
Suzuki K Poulose <suzuki.poulose@....com>,
Zenghui Yu <yuzenghui@...wei.com>,
linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org,
Joey Gouly <joey.gouly@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Christoffer Dall <christoffer.dall@....com>,
Fuad Tabba <tabba@...gle.com>,
linux-coco@...ts.linux.dev,
Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
Gavin Shan <gshan@...hat.com>,
Shanker Donthineni <sdonthineni@...dia.com>,
Alper Gun <alpergun@...gle.com>
Subject: [PATCH v4 23/43] KVM: arm64: Validate register access for a Realm VM
The RMM only allows setting the lower GPRS (x0-x7) and PC for a realm
guest. Check this in kvm_arm_set_reg() so that the VMM can receive a
suitable error return if other registers are accessed.
Signed-off-by: Steven Price <steven.price@....com>
---
arch/arm64/kvm/guest.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 11098eb7eb44..8066d3f05403 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -783,12 +783,38 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
return kvm_arm_sys_reg_get_reg(vcpu, reg);
}
+/*
+ * The RMI ABI only enables setting the lower GPRs (x0-x7) and PC.
+ * All other registers are reset to architectural or otherwise defined reset
+ * values by the RMM, except for a few configuration fields that correspond to
+ * Realm parameters.
+ */
+static bool validate_realm_set_reg(struct kvm_vcpu *vcpu,
+ const struct kvm_one_reg *reg)
+{
+ if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE) {
+ u64 off = core_reg_offset_from_id(reg->id);
+
+ switch (off) {
+ case KVM_REG_ARM_CORE_REG(regs.regs[0]) ...
+ KVM_REG_ARM_CORE_REG(regs.regs[7]):
+ case KVM_REG_ARM_CORE_REG(regs.pc):
+ return true;
+ }
+ }
+
+ return false;
+}
+
int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
{
/* We currently use nothing arch-specific in upper 32 bits */
if ((reg->id & ~KVM_REG_SIZE_MASK) >> 32 != KVM_REG_ARM64 >> 32)
return -EINVAL;
+ if (kvm_is_realm(vcpu->kvm) && !validate_realm_set_reg(vcpu, reg))
+ return -EINVAL;
+
switch (reg->id & KVM_REG_ARM_COPROC_MASK) {
case KVM_REG_ARM_CORE: return set_core_reg(vcpu, reg);
case KVM_REG_ARM_FW:
--
2.34.1
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