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[77.7.15.136]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cca3e642dsm35357485e9.2.2026.08.28.22.50.19 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 28 Aug 2026 22:50:20 -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 0/2] KVM: arm64: Return -EINVAL for an empty SMCCC filter range at base 0 Date: Sat, 29 Aug 2026 07:48:54 +0200 Message-Id: <20260829054856.70549-1-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit KVM_ARM_VM_SMCCC_FILTER rejects an empty range (nr_functions == 0) with -EINVAL for every base except 0. kvm_smccc_set_filter() only rejects a range if its inclusive end, base + nr_functions - 1, is below base; for base 0 that end wraps to U32_MAX, and KVM then tries to insert [0, U32_MAX], which overlaps the reserved Arm Architecture Calls ranges, so the attribute returns -EEXIST instead of -EINVAL. The request is rejected either way; only the errno is wrong, so this is a minor UAPI validation fix. Patch 1 rejects a zero function count explicitly. Patch 2 adds the base 0 case to test_invalid_nr_functions(), which only covered a nonzero base and therefore never caught this. Tested on an arm64 KVM host in VHE mode running under QEMU TCG: a small userspace reproducer gets EEXIST before patch 1 and EINVAL after it, and the smccc_filter selftest including the new assertion passes with patch 1 applied and fails at the new assertion with EEXIST without it. Karl Mehltretter (2): KVM: arm64: Return -EINVAL for an empty SMCCC filter range at base 0 KVM: arm64: selftests: Test empty SMCCC filter range at base 0 arch/arm64/kvm/hypercalls.c | 3 ++- tools/testing/selftests/kvm/arm64/smccc_filter.c | 4 ++++ 2 files changed, 6 insertions(+), 1 deletion(-) base-commit: 548e7bcd0c5460ddcbca9600cea603ebeebf4da7 -- 2.39.5 (Apple Git-154)