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R. Silva" , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org Subject: [PATCH 24/82] KVM: arm64: vgic: Refactor intentional wrap-around calculation Date: Mon, 22 Jan 2024 16:26:59 -0800 Message-Id: <20240123002814.1396804-24-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240122235208.work.748-kees@kernel.org> References: <20240122235208.work.748-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3802; i=keescook@chromium.org; h=from:subject; bh=GddXUjJuZ+2bGLFR1fNATJcBu0uRqs+B42yjt68FCHs=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlrwgGWO9y3Y/zEJG45Jiuj5PhDwKbjJDqkH4IS kNGsePCJRqJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZa8IBgAKCRCJcvTf3G3A JqBCD/9v7CKsi/Hp5MouKCy7vLngZngkzYEdtOtxvOJgkUFMmGHIkK2gyz3sJe4U7qqfIEZ0SIH byjwpGGQ+Wkbvqgus0jhOeC7XosIpO5nK83FNGAUV+4MfxCBW9saxE0quwl3Ie+gR1zNXAXEqta HtaMpPyFf4WXUs4KsfbCtnxQHKhYiU+B/tB6lN1SBzRm60x/3cVJuQ20JZ/i/kmandUheqFP0bj A3H9hdaRlfvsDgWjIHJ8Eo1A6vVgRhkgrXPhd4/FenNP/Jz2IdwVDxNxU1ConcuKOt/aA8eavFW 5rnNaKwaIgWZpM9B34AoDY07DSYmMlbC5jIIcFQCG22pmVItHkejUwE8DpLPrBjJWqpd75CkQvm VYPa4oC24OVpGUmyN6LyxhIjaVDqr5Y8WP2GqhwhOFLeq4ndz3iUyyeo+NCs9kbLiCIn+i/8UQd aTUuW4NzKzChhyeYxkQ3DSQ1oglFaVSoG+DZVG9LGK3pG2aGtPMupHfwxlyuGXB/0reNaDiCV4O th9KxB/tcrzhzWw7YGwOeUyw6UHIF8CUu/ecKm8CE8HiwxAxveX29SzicfeLz45rTrGItmaz6Zb 19dbQNQyeeGBES1P35IUEbY7CsxIA6muFz7htulmypE1jgwHu2k/Dv0H0r5e4CdMI5J9gkBbRHw +10i2uWcrpKRsjg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded unsigned wrap-around addition test to use check_add_overflow(), retaining the result for later usage (which removes the redundant open-coded addition). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Marc Zyngier Cc: Oliver Upton Cc: James Morse Cc: Suzuki K Poulose Cc: Zenghui Yu Cc: Catalin Marinas Cc: Will Deacon Cc: Reiji Watanabe Cc: Eric Auger Cc: Ricardo Koller Cc: Raghavendra Rao Ananta Cc: Quentin Perret Cc: Jean-Philippe Brucker Cc: linux-arm-kernel@lists.infradead.org Cc: kvmarm@lists.linux.dev Signed-off-by: Kees Cook Acked-by: Marc Zyngier Reviewed-by: Eric Auger --- arch/arm64/kvm/vgic/vgic-kvm-device.c | 6 ++++-- arch/arm64/kvm/vgic/vgic-v2.c | 10 ++++++---- 2 files changed, 10 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c index f48b8dab8b3d..0eec5344d203 100644 --- a/arch/arm64/kvm/vgic/vgic-kvm-device.c +++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c @@ -18,17 +18,19 @@ int vgic_check_iorange(struct kvm *kvm, phys_addr_t ioaddr, phys_addr_t addr, phys_addr_t alignment, phys_addr_t size) { + phys_addr_t sum; + if (!IS_VGIC_ADDR_UNDEF(ioaddr)) return -EEXIST; if (!IS_ALIGNED(addr, alignment) || !IS_ALIGNED(size, alignment)) return -EINVAL; - if (addr + size < addr) + if (check_add_overflow(addr, size, &sum)) return -EINVAL; if (addr & ~kvm_phys_mask(&kvm->arch.mmu) || - (addr + size) > kvm_phys_size(&kvm->arch.mmu)) + sum > kvm_phys_size(&kvm->arch.mmu)) return -E2BIG; return 0; diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c index 7e9cdb78f7ce..c8d1e965d3b7 100644 --- a/arch/arm64/kvm/vgic/vgic-v2.c +++ b/arch/arm64/kvm/vgic/vgic-v2.c @@ -273,14 +273,16 @@ void vgic_v2_enable(struct kvm_vcpu *vcpu) /* check for overlapping regions and for regions crossing the end of memory */ static bool vgic_v2_check_base(gpa_t dist_base, gpa_t cpu_base) { - if (dist_base + KVM_VGIC_V2_DIST_SIZE < dist_base) + gpa_t dist_sum, cpu_sum; + + if (check_add_overflow(dist_base, KVM_VGIC_V2_DIST_SIZE, &dist_sum)) return false; - if (cpu_base + KVM_VGIC_V2_CPU_SIZE < cpu_base) + if (check_add_overflow(cpu_base, KVM_VGIC_V2_CPU_SIZE, &cpu_sum)) return false; - if (dist_base + KVM_VGIC_V2_DIST_SIZE <= cpu_base) + if (dist_sum <= cpu_base) return true; - if (cpu_base + KVM_VGIC_V2_CPU_SIZE <= dist_base) + if (cpu_sum <= dist_base) return true; return false;