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CVE-2015-0239 kvm: insufficient sysenter emulation from 16-bit (rhbz 1186448 1186453)

This commit is contained in:
Josh Boyer 2015-01-27 12:16:46 -05:00
parent aa7180f4aa
commit aaa68966b7
2 changed files with 91 additions and 0 deletions
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81
KVM-x86-SYSENTER-emulation-is-broken.patch Normal file
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@ -0,0 +1,81 @@
From: Nadav Amit <namit@cs.technion.ac.il>
Date: Thu, 1 Jan 2015 23:11:11 +0200
Subject: [PATCH] KVM: x86: SYSENTER emulation is broken
SYSENTER emulation is broken in several ways:
1. It misses the case of 16-bit code segments completely (CVE-2015-0239).
2. MSR_IA32_SYSENTER_CS is checked in 64-bit mode incorrectly (bits 0 and 1 can
still be set without causing #GP).
3. MSR_IA32_SYSENTER_EIP and MSR_IA32_SYSENTER_ESP are not masked in
legacy-mode.
4. There is some unneeded code.
Fix it.
Cc: stable@vger.linux.org
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/emulate.c | 27 ++++++++-------------------
1 file changed, 8 insertions(+), 19 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 22e7ed9e6d8e..ac640d47c28d 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2345,7 +2345,7 @@ static int em_sysenter(struct x86_emulate_ctxt *ctxt)
* Not recognized on AMD in compat mode (but is recognized in legacy
* mode).
*/
- if ((ctxt->mode == X86EMUL_MODE_PROT32) && (efer & EFER_LMA)
+ if ((ctxt->mode != X86EMUL_MODE_PROT64) && (efer & EFER_LMA)
&& !vendor_intel(ctxt))
return emulate_ud(ctxt);
@@ -2358,25 +2358,13 @@ static int em_sysenter(struct x86_emulate_ctxt *ctxt)
setup_syscalls_segments(ctxt, &cs, &ss);
ops->get_msr(ctxt, MSR_IA32_SYSENTER_CS, &msr_data);
- switch (ctxt->mode) {
- case X86EMUL_MODE_PROT32:
- if ((msr_data & 0xfffc) == 0x0)
- return emulate_gp(ctxt, 0);
- break;
- case X86EMUL_MODE_PROT64:
- if (msr_data == 0x0)
- return emulate_gp(ctxt, 0);
- break;
- default:
- break;
- }
+ if ((msr_data & 0xfffc) == 0x0)
+ return emulate_gp(ctxt, 0);
ctxt->eflags &= ~(EFLG_VM | EFLG_IF);
- cs_sel = (u16)msr_data;
- cs_sel &= ~SELECTOR_RPL_MASK;
+ cs_sel = (u16)msr_data & ~SELECTOR_RPL_MASK;
ss_sel = cs_sel + 8;
- ss_sel &= ~SELECTOR_RPL_MASK;
- if (ctxt->mode == X86EMUL_MODE_PROT64 || (efer & EFER_LMA)) {
+ if (efer & EFER_LMA) {
cs.d = 0;
cs.l = 1;
}
@@ -2385,10 +2373,11 @@ static int em_sysenter(struct x86_emulate_ctxt *ctxt)
ops->set_segment(ctxt, ss_sel, &ss, 0, VCPU_SREG_SS);
ops->get_msr(ctxt, MSR_IA32_SYSENTER_EIP, &msr_data);
- ctxt->_eip = msr_data;
+ ctxt->_eip = (efer & EFER_LMA) ? msr_data : (u32)msr_data;
ops->get_msr(ctxt, MSR_IA32_SYSENTER_ESP, &msr_data);
- *reg_write(ctxt, VCPU_REGS_RSP) = msr_data;
+ *reg_write(ctxt, VCPU_REGS_RSP) = (efer & EFER_LMA) ? msr_data :
+ (u32)msr_data;
return X86EMUL_CONTINUE;
}
--
2.1.0

10
kernel.spec
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@ -653,6 +653,10 @@ Patch30001: mpssd-x86-only.patch
Patch30002: stable-3.18.4-queue.patch
Patch30003: xhci-check-if-slot-is-already-in-default-state.patch
#CVE-2015-0239 rhbz 1186448 1186453
Patch30004: KVM-x86-SYSENTER-emulation-is-broken.patch
# END OF PATCH DEFINITIONS
%endif
@ -1411,6 +1415,9 @@ ApplyPatch mpssd-x86-only.patch
ApplyPatch stable-3.18.4-queue.patch
ApplyPatch xhci-check-if-slot-is-already-in-default-state.patch
#CVE-2015-0239 rhbz 1186448 1186453
ApplyPatch KVM-x86-SYSENTER-emulation-is-broken.patch
%if 0%{?aarch64patches}
ApplyPatch kernel-arm64.patch
%ifnarch aarch64 # this is stupid, but i want to notice before secondary koji does.
@ -2281,6 +2288,9 @@ fi
# ||----w |
# || ||
%changelog
* Tue Jan 27 2015 Josh Boyer <jwboyer@fedoraproject.org>
- CVE-2015-0239 kvm: insufficient sysenter emulation from 16-bit (rhbz 1186448 1186453)
* Mon Jan 19 2015 Justin M. Forbes <jforbes@fedoraproject.org> - 3.18.3-201
- Add fixes from 3.18.4 queue to fix i915 issues (rhbz 1183232)
- xhci: Check if slot is already in default state before moving it there (rhbz 1183289)