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[77.7.15.136]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cca3e642dsm35357485e9.2.2026.08.28.22.50.21 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 28 Aug 2026 22:50:22 -0700 (PDT) From: Karl Mehltretter To: Marc Zyngier , Oliver Upton , kvmarm@lists.linux.dev Cc: Karl Mehltretter , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , Paolo Bonzini , Sean Christopherson , Shuah Khan , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH 1/2] KVM: arm64: Return -EINVAL for an empty SMCCC filter range at base 0 Date: Sat, 29 Aug 2026 07:48:55 +0200 Message-Id: <20260829054856.70549-2-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20260829054856.70549-1-kmehltretter@gmail.com> References: <20260829054856.70549-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit kvm_smccc_set_filter() only rejects a range if its inclusive end, base + nr_functions - 1, is below base. That catches an empty range (nr_functions == 0) at every nonzero base, but at base 0 the end wraps to U32_MAX and KVM tries to insert [0, U32_MAX], which overlaps the reserved Arm Architecture Calls ranges. KVM_ARM_VM_SMCCC_FILTER then returns -EEXIST instead of the -EINVAL that the smccc_filter selftest expects for an empty range. Reject a zero function count explicitly. Tested with a userspace reproducer on an arm64 VHE host under QEMU TCG: EEXIST before, EINVAL after. Fixes: 821d935c87bc ("KVM: arm64: Introduce support for userspace SMCCC filtering") Assisted-by: LLM Signed-off-by: Karl Mehltretter --- arch/arm64/kvm/hypercalls.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c index b11b8821c9fb..dfa25bb6f25d 100644 --- a/arch/arm64/kvm/hypercalls.c +++ b/arch/arm64/kvm/hypercalls.c @@ -185,7 +185,8 @@ static int kvm_smccc_set_filter(struct kvm *kvm, struct kvm_smccc_filter __user start = filter.base; end = start + filter.nr_functions - 1; - if (end < start || filter.action >= NR_SMCCC_FILTER_ACTIONS) + if (!filter.nr_functions || end < start || + filter.action >= NR_SMCCC_FILTER_ACTIONS) return -EINVAL; mutex_lock(&kvm->arch.config_lock); -- 2.39.5 (Apple Git-154)