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| author | Paolo Bonzini <pbonzini@redhat.com> | 2018-06-06 18:38:09 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-06-16 10:18:20 +0300 |
| commit | 0c950f7417267db597e73170d7694ba7f09f77a0 (patch) | |
| tree | 24afa9d28ba493c188967aed9d832378f5ac597d /arch/x86/kvm/x86.c | |
| parent | 3842b793ee401393f2befdd39d22d1fea6b5c5a2 (diff) | |
| download | linux-0c950f7417267db597e73170d7694ba7f09f77a0.tar.xz | |
kvm: x86: use correct privilege level for sgdt/sidt/fxsave/fxrstor access
commit 3c9fa24ca7c9c47605672916491f79e8ccacb9e6 upstream.
The functions that were used in the emulation of fxrstor, fxsave, sgdt and
sidt were originally meant for task switching, and as such they did not
check privilege levels. This is very bad when the same functions are used
in the emulation of unprivileged instructions. This is CVE-2018-10853.
The obvious fix is to add a new argument to ops->read_std and ops->write_std,
which decides whether the access is a "system" access or should use the
processor's CPL.
Fixes: 129a72a0d3c8 ("KVM: x86: Introduce segmented_write_std", 2017-01-12)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/x86/kvm/x86.c')
| -rw-r--r-- | arch/x86/kvm/x86.c | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1fcdb3489c28..fbc4d17e3ecc 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4800,10 +4800,15 @@ EXPORT_SYMBOL_GPL(kvm_read_guest_virt); static int emulator_read_std(struct x86_emulate_ctxt *ctxt, gva_t addr, void *val, unsigned int bytes, - struct x86_exception *exception) + struct x86_exception *exception, bool system) { struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); - return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, 0, exception); + u32 access = 0; + + if (!system && kvm_x86_ops->get_cpl(vcpu) == 3) + access |= PFERR_USER_MASK; + + return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, access, exception); } static int kvm_read_guest_phys_system(struct x86_emulate_ctxt *ctxt, @@ -4847,12 +4852,17 @@ out: } static int emulator_write_std(struct x86_emulate_ctxt *ctxt, gva_t addr, void *val, - unsigned int bytes, struct x86_exception *exception) + unsigned int bytes, struct x86_exception *exception, + bool system) { struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); + u32 access = PFERR_WRITE_MASK; + + if (!system && kvm_x86_ops->get_cpl(vcpu) == 3) + access |= PFERR_USER_MASK; return kvm_write_guest_virt_helper(addr, val, bytes, vcpu, - PFERR_WRITE_MASK, exception); + access, exception); } int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu, gva_t addr, void *val, @@ -4871,8 +4881,8 @@ int handle_ud(struct kvm_vcpu *vcpu) struct x86_exception e; if (force_emulation_prefix && - kvm_read_guest_virt(&vcpu->arch.emulate_ctxt, - kvm_get_linear_rip(vcpu), sig, sizeof(sig), &e) == 0 && + kvm_read_guest_virt(vcpu, kvm_get_linear_rip(vcpu), + sig, sizeof(sig), &e) == 0 && memcmp(sig, "\xf\xbkvm", sizeof(sig)) == 0) { kvm_rip_write(vcpu, kvm_rip_read(vcpu) + sizeof(sig)); emul_type = 0; |