From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762054AbbA1WYZ (ORCPT ); Wed, 28 Jan 2015 17:24:25 -0500 Received: from mail-wi0-f172.google.com ([209.85.212.172]:63451 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752082AbbA1ULm convert rfc822-to-8bit (ORCPT ); Wed, 28 Jan 2015 15:11:42 -0500 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 8.1 \(1993\)) Subject: Re: [PATCH 3.4 081/177] KVM: x86: Emulator fixes for eip canonical checks on near branches From: Nadav Amit In-Reply-To: <1422418236-12852-161-git-send-email-lizf@kernel.org> Date: Wed, 28 Jan 2015 10:49:16 +0200 Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, Nadav Amit , Paolo Bonzini , Zefan Li Content-Transfer-Encoding: 8BIT Message-Id: References: <1422418050-12581-1-git-send-email-lizf@kernel.org> <1422418236-12852-161-git-send-email-lizf@kernel.org> To: lizf@kernel.org X-Mailer: Apple Mail (2.1993) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is a bug in this patch, so please include 7e46dddd6f6cd5dbf3c7bd04a7e75d19475ac9f2 ("KVM: x86: Fix far-jump to non-canonical check”) as well. Regards, Nadav lizf@kernel.org wrote: > From: Nadav Amit > > 3.4.106-rc1 review patch. If anyone has any objections, please let me know. > > ------------------ > > > commit 234f3ce485d54017f15cf5e0699cff4100121601 upstream. > > Before changing rip (during jmp, call, ret, etc.) the target should be asserted > to be canonical one, as real CPUs do. During sysret, both target rsp and rip > should be canonical. If any of these values is noncanonical, a #GP exception > should occur. The exception to this rule are syscall and sysenter instructions > in which the assigned rip is checked during the assignment to the relevant > MSRs. > > This patch fixes the emulator to behave as real CPUs do for near branches. > Far branches are handled by the next patch. > > This fixes CVE-2014-3647. > > Signed-off-by: Nadav Amit > Signed-off-by: Paolo Bonzini > [lizf: Backported to 3.4: > - adjust context > - use ctxt->regs rather than reg_read() and reg_write()] > Signed-off-by: Zefan Li > --- > arch/x86/kvm/emulate.c | 78 ++++++++++++++++++++++++++++++++++---------------- > 1 file changed, 54 insertions(+), 24 deletions(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index fa23346..c3e1942 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -532,7 +532,8 @@ static int emulate_nm(struct x86_emulate_ctxt *ctxt) > return emulate_exception(ctxt, NM_VECTOR, 0, false); > } > > -static inline void assign_eip_near(struct x86_emulate_ctxt *ctxt, ulong dst) > +static inline int assign_eip_far(struct x86_emulate_ctxt *ctxt, ulong dst, > + int cs_l) > { > switch (ctxt->op_bytes) { > case 2: > @@ -542,16 +543,25 @@ static inline void assign_eip_near(struct x86_emulate_ctxt *ctxt, ulong dst) > ctxt->_eip = (u32)dst; > break; > case 8: > + if ((cs_l && is_noncanonical_address(dst)) || > + (!cs_l && (dst & ~(u32)-1))) > + return emulate_gp(ctxt, 0); > ctxt->_eip = dst; > break; > default: > WARN(1, "unsupported eip assignment size\n"); > } > + return X86EMUL_CONTINUE; > +} > + > +static inline int assign_eip_near(struct x86_emulate_ctxt *ctxt, ulong dst) > +{ > + return assign_eip_far(ctxt, dst, ctxt->mode == X86EMUL_MODE_PROT64); > } > > -static inline void jmp_rel(struct x86_emulate_ctxt *ctxt, int rel) > +static inline int jmp_rel(struct x86_emulate_ctxt *ctxt, int rel) > { > - assign_eip_near(ctxt, ctxt->_eip + rel); > + return assign_eip_near(ctxt, ctxt->_eip + rel); > } > > static u16 get_segment_selector(struct x86_emulate_ctxt *ctxt, unsigned seg) > @@ -1802,13 +1812,15 @@ static int em_grp45(struct x86_emulate_ctxt *ctxt) > case 2: /* call near abs */ { > long int old_eip; > old_eip = ctxt->_eip; > - ctxt->_eip = ctxt->src.val; > + rc = assign_eip_near(ctxt, ctxt->src.val); > + if (rc != X86EMUL_CONTINUE) > + break; > ctxt->src.val = old_eip; > rc = em_push(ctxt); > break; > } > case 4: /* jmp abs */ > - ctxt->_eip = ctxt->src.val; > + rc = assign_eip_near(ctxt, ctxt->src.val); > break; > case 5: /* jmp far */ > rc = em_jmp_far(ctxt); > @@ -1840,10 +1852,14 @@ static int em_cmpxchg8b(struct x86_emulate_ctxt *ctxt) > > static int em_ret(struct x86_emulate_ctxt *ctxt) > { > - ctxt->dst.type = OP_REG; > - ctxt->dst.addr.reg = &ctxt->_eip; > - ctxt->dst.bytes = ctxt->op_bytes; > - return em_pop(ctxt); > + int rc; > + unsigned long eip; > + > + rc = emulate_pop(ctxt, &eip, ctxt->op_bytes); > + if (rc != X86EMUL_CONTINUE) > + return rc; > + > + return assign_eip_near(ctxt, eip); > } > > static int em_ret_far(struct x86_emulate_ctxt *ctxt) > @@ -2108,7 +2124,7 @@ static int em_sysexit(struct x86_emulate_ctxt *ctxt) > { > struct x86_emulate_ops *ops = ctxt->ops; > struct desc_struct cs, ss; > - u64 msr_data; > + u64 msr_data, rcx, rdx; > int usermode; > u16 cs_sel = 0, ss_sel = 0; > > @@ -2124,6 +2140,9 @@ static int em_sysexit(struct x86_emulate_ctxt *ctxt) > else > usermode = X86EMUL_MODE_PROT32; > > + rcx = ctxt->regs[VCPU_REGS_RCX]; > + rdx = ctxt->regs[VCPU_REGS_RDX]; > + > cs.dpl = 3; > ss.dpl = 3; > ops->get_msr(ctxt, MSR_IA32_SYSENTER_CS, &msr_data); > @@ -2141,6 +2160,9 @@ static int em_sysexit(struct x86_emulate_ctxt *ctxt) > ss_sel = cs_sel + 8; > cs.d = 0; > cs.l = 1; > + if (is_noncanonical_address(rcx) || > + is_noncanonical_address(rdx)) > + return emulate_gp(ctxt, 0); > break; > } > cs_sel |= SELECTOR_RPL_MASK; > @@ -2149,8 +2171,8 @@ static int em_sysexit(struct x86_emulate_ctxt *ctxt) > ops->set_segment(ctxt, cs_sel, &cs, 0, VCPU_SREG_CS); > ops->set_segment(ctxt, ss_sel, &ss, 0, VCPU_SREG_SS); > > - ctxt->_eip = ctxt->regs[VCPU_REGS_RDX]; > - ctxt->regs[VCPU_REGS_RSP] = ctxt->regs[VCPU_REGS_RCX]; > + ctxt->_eip = rdx; > + ctxt->regs[VCPU_REGS_RSP] = rcx; > > return X86EMUL_CONTINUE; > } > @@ -2646,10 +2668,13 @@ static int em_das(struct x86_emulate_ctxt *ctxt) > > static int em_call(struct x86_emulate_ctxt *ctxt) > { > + int rc; > long rel = ctxt->src.val; > > ctxt->src.val = (unsigned long)ctxt->_eip; > - jmp_rel(ctxt, rel); > + rc = jmp_rel(ctxt, rel); > + if (rc != X86EMUL_CONTINUE) > + return rc; > return em_push(ctxt); > } > > @@ -2681,11 +2706,12 @@ static int em_call_far(struct x86_emulate_ctxt *ctxt) > static int em_ret_near_imm(struct x86_emulate_ctxt *ctxt) > { > int rc; > + unsigned long eip; > > - ctxt->dst.type = OP_REG; > - ctxt->dst.addr.reg = &ctxt->_eip; > - ctxt->dst.bytes = ctxt->op_bytes; > - rc = emulate_pop(ctxt, &ctxt->dst.val, ctxt->op_bytes); > + rc = emulate_pop(ctxt, &eip, ctxt->op_bytes); > + if (rc != X86EMUL_CONTINUE) > + return rc; > + rc = assign_eip_near(ctxt, eip); > if (rc != X86EMUL_CONTINUE) > return rc; > register_address_increment(ctxt, &ctxt->regs[VCPU_REGS_RSP], ctxt->src.val); > @@ -2994,20 +3020,24 @@ static int em_lmsw(struct x86_emulate_ctxt *ctxt) > > static int em_loop(struct x86_emulate_ctxt *ctxt) > { > + int rc = X86EMUL_CONTINUE; > + > register_address_increment(ctxt, &ctxt->regs[VCPU_REGS_RCX], -1); > if ((address_mask(ctxt, ctxt->regs[VCPU_REGS_RCX]) != 0) && > (ctxt->b == 0xe2 || test_cc(ctxt->b ^ 0x5, ctxt->eflags))) > - jmp_rel(ctxt, ctxt->src.val); > + rc = jmp_rel(ctxt, ctxt->src.val); > > - return X86EMUL_CONTINUE; > + return rc; > } > > static int em_jcxz(struct x86_emulate_ctxt *ctxt) > { > + int rc = X86EMUL_CONTINUE; > + > if (address_mask(ctxt, ctxt->regs[VCPU_REGS_RCX]) == 0) > - jmp_rel(ctxt, ctxt->src.val); > + rc = jmp_rel(ctxt, ctxt->src.val); > > - return X86EMUL_CONTINUE; > + return rc; > } > > static int em_in(struct x86_emulate_ctxt *ctxt) > @@ -4185,7 +4215,7 @@ special_insn: > break; > case 0x70 ... 0x7f: /* jcc (short) */ > if (test_cc(ctxt->b, ctxt->eflags)) > - jmp_rel(ctxt, ctxt->src.val); > + rc = jmp_rel(ctxt, ctxt->src.val); > break; > case 0x8d: /* lea r16/r32, m */ > ctxt->dst.val = ctxt->src.addr.mem.ea; > @@ -4224,7 +4254,7 @@ special_insn: > break; > case 0xe9: /* jmp rel */ > case 0xeb: /* jmp rel short */ > - jmp_rel(ctxt, ctxt->src.val); > + rc = jmp_rel(ctxt, ctxt->src.val); > ctxt->dst.type = OP_NONE; /* Disable writeback. */ > break; > case 0xf4: /* hlt */ > @@ -4327,7 +4357,7 @@ twobyte_insn: > break; > case 0x80 ... 0x8f: /* jnz rel, etc*/ > if (test_cc(ctxt->b, ctxt->eflags)) > - jmp_rel(ctxt, ctxt->src.val); > + rc = jmp_rel(ctxt, ctxt->src.val); > break; > case 0x90 ... 0x9f: /* setcc r/m8 */ > ctxt->dst.val = test_cc(ctxt->b, ctxt->eflags); > -- > 1.9.1