This is a note to let you know that I've just added the patch titled
KVM: x86: invalid opcode oops on SET_SREGS with OSXSAVE bit set (CVE-2012-4461)
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-invalid-opcode-oops-on-set_sregs-with-osxsave-bit-set-cve-2012-4461.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From jslaby@xxxxxxx Mon Apr 1 16:38:00 2013
From: Jiri Slaby <jslaby@xxxxxxx>
Date: Tue, 19 Mar 2013 12:36:59 +0100
Subject: KVM: x86: invalid opcode oops on SET_SREGS with OSXSAVE bit set (CVE-2012-4461)
To: gregkh@xxxxxxxxxxxxxxxxxxx
Cc: jirislaby@xxxxxxxxx, stable@xxxxxxxxxxxxxxx, Petr Matousek <pmatouse@xxxxxxxxxx>, Marcelo Tosatti <mtosatti@xxxxxxxxxx>, Jiri Slaby <jslaby@xxxxxxx>
Message-ID: <1363693019-14812-14-git-send-email-jslaby@xxxxxxx>
From: Petr Matousek <pmatouse@xxxxxxxxxx>
commit 6d1068b3a98519247d8ba4ec85cd40ac136dbdf9 upstream.
On hosts without the XSAVE support unprivileged local user can trigger
oops similar to the one below by setting X86_CR4_OSXSAVE bit in guest
cr4 register using KVM_SET_SREGS ioctl and later issuing KVM_RUN
ioctl.
invalid opcode: 0000 [#2] SMP
Modules linked in: tun ip6table_filter ip6_tables ebtable_nat ebtables
...
Pid: 24935, comm: zoog_kvm_monito Tainted: G D 3.2.0-3-686-pae
EIP: 0060:[<f8b9550c>] EFLAGS: 00210246 CPU: 0
EIP is at kvm_arch_vcpu_ioctl_run+0x92a/0xd13 [kvm]
EAX: 00000001 EBX: 000f387e ECX: 00000000 EDX: 00000000
ESI: 00000000 EDI: 00000000 EBP: ef5a0060 ESP: d7c63e70
DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
Process zoog_kvm_monito (pid: 24935, ti=d7c62000 task=ed84a0c0
task.ti=d7c62000)
Stack:
00000001 f70a1200 f8b940a9 ef5a0060 00000000 00200202 f8769009 00000000
ef5a0060 000f387e eda5c020 8722f9c8 00015bae 00000000 ed84a0c0 ed84a0c0
c12bf02d 0000ae80 ef7f8740 fffffffb f359b740 ef5a0060 f8b85dc1 0000ae80
Call Trace:
[<f8b940a9>] ? kvm_arch_vcpu_ioctl_set_sregs+0x2fe/0x308 [kvm]
...
[<c12bfb44>] ? syscall_call+0x7/0xb
Code: 89 e8 e8 14 ee ff ff ba 00 00 04 00 89 e8 e8 98 48 ff ff 85 c0 74
1e 83 7d 48 00 75 18 8b 85 08 07 00 00 31 c9 8b 95 0c 07 00 00 <0f> 01
d1 c7 45 48 01 00 00 00 c7 45 1c 01 00 00 00 0f ae f0 89
EIP: [<f8b9550c>] kvm_arch_vcpu_ioctl_run+0x92a/0xd13 [kvm] SS:ESP
0068:d7c63e70
QEMU first retrieves the supported features via KVM_GET_SUPPORTED_CPUID
and then sets them later. So guest's X86_FEATURE_XSAVE should be masked
out on hosts without X86_FEATURE_XSAVE, making kvm_set_cr4 with
X86_CR4_OSXSAVE fail. Userspaces that allow specifying guest cpuid with
X86_FEATURE_XSAVE even on hosts that do not support it, might be
susceptible to this attack from inside the guest as well.
Allow setting X86_CR4_OSXSAVE bit only if host has XSAVE support.
Signed-off-by: Petr Matousek <pmatouse@xxxxxxxxxx>
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -575,6 +575,9 @@ static bool guest_cpuid_has_xsave(struct
{
struct kvm_cpuid_entry2 *best;
+ if (!cpu_has_xsave)
+ return 0;
+
best = kvm_find_cpuid_entry(vcpu, 1, 0);
return best && (best->ecx & bit(X86_FEATURE_XSAVE));
}
@@ -5854,6 +5857,9 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct
int pending_vec, max_bits, idx;
struct desc_ptr dt;
+ if (!guest_cpuid_has_xsave(vcpu) && (sregs->cr4 & X86_CR4_OSXSAVE))
+ return -EINVAL;
+
dt.size = sregs->idt.limit;
dt.address = sregs->idt.base;
kvm_x86_ops->set_idt(vcpu, &dt);
Patches currently in stable-queue which might be from jslaby@xxxxxxx are
queue-3.0/kvm-x86-prevent-starting-pit-timers-in-the-absence-of-irqchip-support.patch
queue-3.0/kvm-x86-invalid-opcode-oops-on-set_sregs-with-osxsave-bit-set-cve-2012-4461.patch
queue-3.0/mm-hotplug-correctly-add-new-zone-to-all-other-nodes-zone-lists.patch
queue-3.0/macvtap-zerocopy-validate-vectors-before-building-skb.patch
queue-3.0/x25-validate-incoming-call-user-data-lengths.patch
queue-3.0/batman-adv-bat_socket_read-missing-checks.patch
queue-3.0/kvm-fix-buffer-overflow-in-kvm_set_irq.patch
queue-3.0/x25-handle-undersized-fragmented-skbs.patch
queue-3.0/nfsv4-include-bitmap-in-nfsv4-get-acl-data.patch
queue-3.0/nfs-nfs_getaclargs.acl_len-is-a-size_t.patch
queue-3.0/nfsv4-fix-an-oops-in-the-nfsv4-getacl-code.patch
queue-3.0/kvm-clean-up-error-handling-during-vcpu-creation.patch
queue-3.0/kvm-ensure-all-vcpus-are-consistent-with-in-kernel-irqchip-settings.patch
queue-3.0/batman-adv-only-write-requested-number-of-byte-to-user-buffer.patch
--
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