4.18-stable review patch. If anyone has any objections, please let me know.
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From: Dave Martin Dave.Martin@arm.com
commit d26c25a9d19b5976b319af528886f89cf455692d upstream.
We currently allow userspace to access the core register file in about any possible way, including straddling multiple registers and doing unaligned accesses.
This is not the expected use of the ABI, and nobody is actually using it that way. Let's tighten it by explicitly checking the size and alignment for each field of the register file.
Cc: stable@vger.kernel.org Fixes: 2f4a07c5f9fe ("arm64: KVM: guest one-reg interface") Reviewed-by: Christoffer Dall christoffer.dall@arm.com Reviewed-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Dave Martin Dave.Martin@arm.com [maz: rewrote Dave's initial patch to be more easily backported] Signed-off-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/kvm/guest.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+)
--- a/arch/arm64/kvm/guest.c +++ b/arch/arm64/kvm/guest.c @@ -57,6 +57,45 @@ static u64 core_reg_offset_from_id(u64 i return id & ~(KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK | KVM_REG_ARM_CORE); }
+static int validate_core_offset(const struct kvm_one_reg *reg) +{ + u64 off = core_reg_offset_from_id(reg->id); + int size; + + switch (off) { + case KVM_REG_ARM_CORE_REG(regs.regs[0]) ... + KVM_REG_ARM_CORE_REG(regs.regs[30]): + case KVM_REG_ARM_CORE_REG(regs.sp): + case KVM_REG_ARM_CORE_REG(regs.pc): + case KVM_REG_ARM_CORE_REG(regs.pstate): + case KVM_REG_ARM_CORE_REG(sp_el1): + case KVM_REG_ARM_CORE_REG(elr_el1): + case KVM_REG_ARM_CORE_REG(spsr[0]) ... + KVM_REG_ARM_CORE_REG(spsr[KVM_NR_SPSR - 1]): + size = sizeof(__u64); + break; + + case KVM_REG_ARM_CORE_REG(fp_regs.vregs[0]) ... + KVM_REG_ARM_CORE_REG(fp_regs.vregs[31]): + size = sizeof(__uint128_t); + break; + + case KVM_REG_ARM_CORE_REG(fp_regs.fpsr): + case KVM_REG_ARM_CORE_REG(fp_regs.fpcr): + size = sizeof(__u32); + break; + + default: + return -EINVAL; + } + + if (KVM_REG_SIZE(reg->id) == size && + IS_ALIGNED(off, size / sizeof(__u32))) + return 0; + + return -EINVAL; +} + static int get_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg) { /* @@ -76,6 +115,9 @@ static int get_core_reg(struct kvm_vcpu (off + (KVM_REG_SIZE(reg->id) / sizeof(__u32))) >= nr_regs) return -ENOENT;
+ if (validate_core_offset(reg)) + return -EINVAL; + if (copy_to_user(uaddr, ((u32 *)regs) + off, KVM_REG_SIZE(reg->id))) return -EFAULT;
@@ -98,6 +140,9 @@ static int set_core_reg(struct kvm_vcpu (off + (KVM_REG_SIZE(reg->id) / sizeof(__u32))) >= nr_regs) return -ENOENT;
+ if (validate_core_offset(reg)) + return -EINVAL; + if (KVM_REG_SIZE(reg->id) > sizeof(tmp)) return -EINVAL;