From 96b2d7a83a27fbae10fc57c39577a7e2689d9f0a Mon Sep 17 00:00:00 2001 From: Hendrik Brueckner Date: Fri, 12 Jun 2015 13:53:51 +0200 Subject: [PATCH] s390/kvm: validate the floating-point control before restoring it The kvm_arch_vcpu_load() does not validate whether the floating-point control (FPC) is valid. Further, the return code of the restore is not checked too. If the FPC is invalid, the restore fails and the host FPC value might remain. The correct behavior would be to clear the FPC if it is not valid. Hence, validate the FPC value and, optionally, reset the value before restoring it. Reviewed-by: David Hildenbrand Signed-off-by: Hendrik Brueckner Signed-off-by: Martin Schwidefsky --- arch/s390/kvm/kvm-s390.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 2078f92d15ac..fc7bc7118b23 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -1200,6 +1200,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu) void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { + __u32 fpc; + save_fp_ctl(&vcpu->arch.host_fpregs.fpc); if (test_kvm_facility(vcpu->kvm, 129)) save_vx_regs((__vector128 *)&vcpu->arch.host_vregs->vrs); @@ -1207,12 +1209,16 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) save_fp_regs(vcpu->arch.host_fpregs.fprs); save_access_regs(vcpu->arch.host_acrs); if (test_kvm_facility(vcpu->kvm, 129)) { - restore_fp_ctl(&vcpu->run->s.regs.fpc); + fpc = vcpu->run->s.regs.fpc; restore_vx_regs((__vector128 *)&vcpu->run->s.regs.vrs); } else { - restore_fp_ctl(&vcpu->arch.guest_fpregs.fpc); + fpc = vcpu->arch.guest_fpregs.fpc; restore_fp_regs(vcpu->arch.guest_fpregs.fprs); } + if (test_fp_ctl(fpc)) + /* User space provided an invalid FPC, let's clear it */ + fpc = 0; + restore_fp_ctl(&fpc); restore_access_regs(vcpu->run->s.regs.acrs); gmap_enable(vcpu->arch.gmap); atomic_set_mask(CPUSTAT_RUNNING, &vcpu->arch.sie_block->cpuflags); -- 2.20.1