linux-kernel - [34-longterm 056/209] KVM: x86: fix information leak to userland

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Date:	Thu, 14 Apr 2011 13:41:26 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, Vasiliy Kulikov <segooon@...il.com>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 056/209] KVM: x86: fix information leak to userland

From: Vasiliy Kulikov <segooon@...il.com>

  =====================================================================
  | This is a commit scheduled for the next v2.6.34 longterm release. |
  | If you see a problem with using this for longterm, please comment.|
  =====================================================================

commit 97e69aa62f8b5d338d6cff49be09e37cc1262838 upstream.

Structures kvm_vcpu_events, kvm_debugregs, kvm_pit_state2 and
kvm_clock_data are copied to userland with some padding and reserved
fields unitialized.  It leads to leaking of contents of kernel stack
memory.  We have to initialize them to zero.

In patch v1 Jan Kiszka suggested to fill reserved fields with zeros
instead of memset'ting the whole struct.  It makes sense as these
fields are explicitly marked as padding.  No more fields need zeroing.

[PG: 34 doesn't have the dbgregs section to be memset, so drop that bit]

KVM-Stable-Tag.
Signed-off-by: Vasiliy Kulikov <segooon@...il.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 arch/x86/kvm/x86.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7ea2888..8ced130 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2115,6 +2115,7 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
 	events->exception.injected = vcpu->arch.exception.pending;
 	events->exception.nr = vcpu->arch.exception.nr;
 	events->exception.has_error_code = vcpu->arch.exception.has_error_code;
+	events->exception.pad = 0;
 	events->exception.error_code = vcpu->arch.exception.error_code;
 
 	events->interrupt.injected = vcpu->arch.interrupt.pending;
@@ -2124,11 +2125,13 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
 	events->nmi.injected = vcpu->arch.nmi_injected;
 	events->nmi.pending = vcpu->arch.nmi_pending;
 	events->nmi.masked = kvm_x86_ops->get_nmi_mask(vcpu);
+	events->nmi.pad = 0;
 
 	events->sipi_vector = vcpu->arch.sipi_vector;
 
 	events->flags = (KVM_VCPUEVENT_VALID_NMI_PENDING
 			 | KVM_VCPUEVENT_VALID_SIPI_VECTOR);
+	memset(&events->reserved, 0, sizeof(events->reserved));
 
 	vcpu_put(vcpu);
 }
@@ -2589,6 +2592,7 @@ static int kvm_vm_ioctl_get_pit2(struct kvm *kvm, struct kvm_pit_state2 *ps)
 		sizeof(ps->channels));
 	ps->flags = kvm->arch.vpit->pit_state.flags;
 	mutex_unlock(&kvm->arch.vpit->pit_state.lock);
+	memset(&ps->reserved, 0, sizeof(ps->reserved));
 	return r;
 }
 
@@ -2983,6 +2987,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		now_ns = timespec_to_ns(&now);
 		user_ns.clock = kvm->arch.kvmclock_offset + now_ns;
 		user_ns.flags = 0;
+		memset(&user_ns.pad, 0, sizeof(user_ns.pad));
 
 		r = -EFAULT;
 		if (copy_to_user(argp, &user_ns, sizeof(user_ns)))
-- 
1.7.4.4

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