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authorAvi Kivity <avi@redhat.com>2010-10-19 16:46:55 +0200
committerMarcelo Tosatti <mtosatti@redhat.com>2010-10-19 14:21:45 -0200
commit9581d442b9058d3699b4be568b6e5eae38a41493 (patch)
tree76d1b596d873514fdb9b3bf75d6d7b3cbfada85d
parent2b666ca4a68cbc22483b0f2e1ba3c0e59b01ae9e (diff)
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KVM: Fix fs/gs reload oops with invalid ldt
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 <avi@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
-rw-r--r--arch/x86/include/asm/kvm_host.h24
-rw-r--r--arch/x86/kvm/svm.c15
-rw-r--r--arch/x86/kvm/vmx.c24
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 502e53f999c..c52e2eb40a1 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -652,20 +652,6 @@ 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;
@@ -673,16 +659,6 @@ 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 81ed28cb36e..8a3f9f64f86 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3163,8 +3163,8 @@ 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 */
@@ -3251,10 +3251,15 @@ 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 49b25eee25a..7bddfab1201 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -803,7 +803,7 @@ 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;
@@ -811,7 +811,7 @@ 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 {
@@ -841,27 +841,21 @@ 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
@@ -2589,8 +2583,8 @@ 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);