linux-kernel - [59/80] KVM: VMX: Fix host GDT.LIMIT corruption

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Message-Id: <20100924162620.022536179@clark.site>
Date:	Fri, 24 Sep 2010 09:24:47 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org, greg@...ah.com
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	avi@...hat.com, mtosatti@...hat.com
Subject: [59/80] KVM: VMX: Fix host GDT.LIMIT corruption

2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------


From: Avi Kivity <avi@...hat.com>

commit 3444d7da1839b851eefedd372978d8a982316c36 upstream.

vmx does not restore GDT.LIMIT to the host value, instead it sets it to 64KB.
This means host userspace can learn a few bits of host memory.

Fix by reloading GDTR when we load other host state.

Signed-off-by: Avi Kivity <avi@...hat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 arch/x86/kvm/vmx.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -177,6 +177,7 @@ static u64 construct_eptp(unsigned long
 static DEFINE_PER_CPU(struct vmcs *, vmxarea);
 static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
 static DEFINE_PER_CPU(struct list_head, vcpus_on_cpu);
+static DEFINE_PER_CPU(struct desc_ptr, host_gdt);
 
 static unsigned long *vmx_io_bitmap_a;
 static unsigned long *vmx_io_bitmap_b;
@@ -812,6 +813,7 @@ static void __vmx_load_host_state(struct
 		wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
 	}
 #endif
+	load_gdt(&__get_cpu_var(host_gdt));
 }
 
 static void vmx_load_host_state(struct vcpu_vmx *vmx)
@@ -1314,6 +1316,8 @@ static int hardware_enable(void *garbage
 
 	ept_sync_global();
 
+	store_gdt(&__get_cpu_var(host_gdt));
+
 	return 0;
 }
 


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