On Sun, 2014-11-02 at 10:44 +0200, Nadav Amit wrote: > Sorry, but this patch is incomplete due to a bug. > The following patch - http://www.spinics.net/lists/kvm/msg109664.html - is needed as well (on top of the previous one). Thanks, I've added that (commit 7e46dddd6f6c). Ben. > Nadav > > > On Nov 2, 2014, at 00:28, Ben Hutchings <ben@xxxxxxxxxxxxxxx> wrote: > > > > 3.2.64-rc1 review patch. If anyone has any objections, please let me know. > > > > ------------------ > > > > From: Nadav Amit <namit@xxxxxxxxxxxxxxxxx> > > > > 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 <namit@xxxxxxxxxxxxxxxxx> > > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > > [bwh: Backported to 3.2: > > - Adjust context > > - Use ctxt->regs[] instead of reg_read(), reg_write(), reg_rmw()] > > Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> > > --- > > arch/x86/kvm/emulate.c | 78 ++++++++++++++++++++++++++++++++++---------------- > > 1 file changed, 54 insertions(+), 24 deletions(-) > > > > --- a/arch/x86/kvm/emulate.c > > +++ b/arch/x86/kvm/emulate.c > > @@ -529,7 +529,8 @@ static int emulate_nm(struct x86_emulate > > 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: > > @@ -539,16 +540,25 @@ static inline void assign_eip_near(struc > > 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) > > @@ -1787,13 +1797,15 @@ static int em_grp45(struct x86_emulate_c > > 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); > > @@ -1825,10 +1837,14 @@ static int em_grp9(struct x86_emulate_ct > > > > 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) > > @@ -2060,7 +2076,7 @@ static int em_sysexit(struct x86_emulate > > { > > 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; > > > > @@ -2076,6 +2092,9 @@ static int em_sysexit(struct x86_emulate > > 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); > > @@ -2093,6 +2112,9 @@ static int em_sysexit(struct x86_emulate > > 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; > > @@ -2101,8 +2123,8 @@ static int em_sysexit(struct x86_emulate > > 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; > > } > > @@ -2555,10 +2577,13 @@ static int em_das(struct x86_emulate_ctx > > > > 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); > > } > > > > @@ -2590,11 +2615,12 @@ static int em_call_far(struct x86_emulat > > 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); > > @@ -2840,20 +2866,24 @@ static int em_lmsw(struct x86_emulate_ct > > > > 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_cli(struct x86_emulate_ctxt *ctxt) > > @@ -3946,7 +3976,7 @@ 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; > > @@ -3994,7 +4024,7 @@ special_insn: > > goto do_io_out; > > 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 0xec: /* in al,dx */ > > @@ -4160,7 +4190,7 @@ 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); > > > -- Ben Hutchings Power corrupts. Absolute power is kind of neat. - John Lehman, Secretary of the US Navy 1981-1987
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