From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755171Ab1ABHcb (ORCPT ); Sun, 2 Jan 2011 02:32:31 -0500 Received: from mail.windriver.com ([147.11.1.11]:37133 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754881Ab1ABHZl (ORCPT ); Sun, 2 Jan 2011 02:25:41 -0500 From: Paul Gortmaker To: stable@kernel.org, linux-kernel@vger.kernel.org Cc: stable-review@kernel.org, Avi Kivity , Marcelo Tosatti , Paul Gortmaker Subject: [34-longterm 238/260] KVM: Fix fs/gs reload oops with invalid ldt Date: Sun, 2 Jan 2011 02:18:54 -0500 Message-Id: <1293952756-15010-239-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.3.3 In-Reply-To: <1293952756-15010-1-git-send-email-paul.gortmaker@windriver.com> References: <1293952756-15010-1-git-send-email-paul.gortmaker@windriver.com> X-OriginalArrivalTime: 02 Jan 2011 07:24:30.0089 (UTC) FILETIME=[183B1F90:01CBAA4E] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Avi Kivity commit 9581d442b9058d3699b4be568b6e5eae38a41493 upstream. kvm reloads the host's fs and gs blindly, however the underlying segment descriptors may be invalid due to the user modifying the ldt after loading them. Fix by using the safe accessors (loadsegment() and load_gs_index()) instead of home grown unsafe versions. This is CVE-2010-3698. KVM-Stable-Tag. Signed-off-by: Avi Kivity Signed-off-by: Marcelo Tosatti Signed-off-by: Paul Gortmaker --- arch/x86/include/asm/kvm_host.h | 24 ------------------------ arch/x86/kvm/svm.c | 15 ++++++++++----- arch/x86/kvm/vmx.c | 24 +++++++++--------------- 3 files changed, 19 insertions(+), 44 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 63400e6..9a6c267 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -691,20 +691,6 @@ static inline struct kvm_mmu_page *page_header(hpa_t shadow_page) return (struct kvm_mmu_page *)page_private(page); } -static inline u16 kvm_read_fs(void) -{ - u16 seg; - asm("mov %%fs, %0" : "=g"(seg)); - return seg; -} - -static inline u16 kvm_read_gs(void) -{ - u16 seg; - asm("mov %%gs, %0" : "=g"(seg)); - return seg; -} - static inline u16 kvm_read_ldt(void) { u16 ldt; @@ -712,16 +698,6 @@ static inline u16 kvm_read_ldt(void) return ldt; } -static inline void kvm_load_fs(u16 sel) -{ - asm("mov %0, %%fs" : : "rm"(sel)); -} - -static inline void kvm_load_gs(u16 sel) -{ - asm("mov %0, %%gs" : : "rm"(sel)); -} - static inline void kvm_load_ldt(u16 sel) { asm("lldt %0" : : "rm"(sel)); diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 80453d4..0d93929 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -2821,8 +2821,8 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) sync_lapic_to_cr8(vcpu); save_host_msrs(vcpu); - fs_selector = kvm_read_fs(); - gs_selector = kvm_read_gs(); + savesegment(fs, fs_selector); + savesegment(gs, gs_selector); ldt_selector = kvm_read_ldt(); svm->vmcb->save.cr2 = vcpu->arch.cr2; /* required for live migration with NPT */ @@ -2909,10 +2909,15 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu) vcpu->arch.regs[VCPU_REGS_RSP] = svm->vmcb->save.rsp; vcpu->arch.regs[VCPU_REGS_RIP] = svm->vmcb->save.rip; - kvm_load_fs(fs_selector); - kvm_load_gs(gs_selector); - kvm_load_ldt(ldt_selector); load_host_msrs(vcpu); + loadsegment(fs, fs_selector); +#ifdef CONFIG_X86_64 + load_gs_index(gs_selector); + wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs); +#else + loadsegment(gs, gs_selector); +#endif + kvm_load_ldt(ldt_selector); reload_tss(vcpu); diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 11db911..2cfa656 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -651,7 +651,7 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu) */ vmx->host_state.ldt_sel = kvm_read_ldt(); vmx->host_state.gs_ldt_reload_needed = vmx->host_state.ldt_sel; - vmx->host_state.fs_sel = kvm_read_fs(); + savesegment(fs, vmx->host_state.fs_sel); if (!(vmx->host_state.fs_sel & 7)) { vmcs_write16(HOST_FS_SELECTOR, vmx->host_state.fs_sel); vmx->host_state.fs_reload_needed = 0; @@ -659,7 +659,7 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu) vmcs_write16(HOST_FS_SELECTOR, 0); vmx->host_state.fs_reload_needed = 1; } - vmx->host_state.gs_sel = kvm_read_gs(); + savesegment(gs, vmx->host_state.gs_sel); if (!(vmx->host_state.gs_sel & 7)) vmcs_write16(HOST_GS_SELECTOR, vmx->host_state.gs_sel); else { @@ -689,27 +689,21 @@ static void vmx_save_host_state(struct kvm_vcpu *vcpu) static void __vmx_load_host_state(struct vcpu_vmx *vmx) { - unsigned long flags; - if (!vmx->host_state.loaded) return; ++vmx->vcpu.stat.host_state_reload; vmx->host_state.loaded = 0; if (vmx->host_state.fs_reload_needed) - kvm_load_fs(vmx->host_state.fs_sel); + loadsegment(fs, vmx->host_state.fs_sel); if (vmx->host_state.gs_ldt_reload_needed) { kvm_load_ldt(vmx->host_state.ldt_sel); - /* - * If we have to reload gs, we must take care to - * preserve our gs base. - */ - local_irq_save(flags); - kvm_load_gs(vmx->host_state.gs_sel); #ifdef CONFIG_X86_64 - wrmsrl(MSR_GS_BASE, vmcs_readl(HOST_GS_BASE)); + load_gs_index(vmx->host_state.gs_sel); + wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs); +#else + loadsegment(gs, vmx->host_state.gs_sel); #endif - local_irq_restore(flags); } reload_tss(); #ifdef CONFIG_X86_64 @@ -2414,8 +2408,8 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx) vmcs_write16(HOST_CS_SELECTOR, __KERNEL_CS); /* 22.2.4 */ vmcs_write16(HOST_DS_SELECTOR, __KERNEL_DS); /* 22.2.4 */ vmcs_write16(HOST_ES_SELECTOR, __KERNEL_DS); /* 22.2.4 */ - vmcs_write16(HOST_FS_SELECTOR, kvm_read_fs()); /* 22.2.4 */ - vmcs_write16(HOST_GS_SELECTOR, kvm_read_gs()); /* 22.2.4 */ + vmcs_write16(HOST_FS_SELECTOR, 0); /* 22.2.4 */ + vmcs_write16(HOST_GS_SELECTOR, 0); /* 22.2.4 */ vmcs_write16(HOST_SS_SELECTOR, __KERNEL_DS); /* 22.2.4 */ #ifdef CONFIG_X86_64 rdmsrl(MSR_FS_BASE, a); -- 1.7.3.3