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SUSE:SLE-12-SP1:GA
xen.10697
56d0339f-x86emul-limit-check-branch-targets.patch
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File 56d0339f-x86emul-limit-check-branch-targets.patch of Package xen.10697
# Commit 81d3a0b26c1672c60b2a54dd8780e6f6472d2328 # Date 2016-02-26 12:14:39 +0100 # Author Jan Beulich <jbeulich@suse.com> # Committer Jan Beulich <jbeulich@suse.com> x86emul: limit-check branch targets All branches need to #GP when their target violates the segment limit (in 16- and 32-bit modes) or is non-canonical (in 64-bit mode). For near branches facilitate this via a zero-byte instruction fetch from the target address (resulting in address translation and validation without an actual read from memory), while far branches get dealt with by breaking up the segment register loading into a read-and-validate part and a write one. The latter at once allows correcting some ordering issues in how the individual emulation steps get carried out: Before updating machine state, all exceptions unrelated to that state updating should have got raised (i.e. the only ones possibly resulting in partly updated state are faulting memory writes [pushes]). Note that while not immediately needed here, write and distinct read emulation routines get updated to deal with zero byte accesses too, for overall consistency. Reported-by: 刘令 <liuling-it@360.cn> Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> Acked-by: Tim Deegan <tim@xen.org> --- a/tools/tests/x86_emulator/x86_emulate.c +++ b/tools/tests/x86_emulator/x86_emulate.c @@ -8,6 +8,8 @@ typedef bool bool_t; +#define is_canonical_address(x) (((int64_t)(x) >> 47) == ((int64_t)(x) >> 63)) + #define BUG() abort() #define ASSERT assert --- a/xen/arch/x86/hvm/emulate.c +++ b/xen/arch/x86/hvm/emulate.c @@ -480,7 +480,7 @@ static int __hvmemul_read( rc = hvmemul_virtual_to_linear( seg, offset, bytes, &reps, access_type, hvmemul_ctxt, &addr); - if ( rc != X86EMUL_OKAY ) + if ( rc != X86EMUL_OKAY || !bytes ) return rc; off = addr & (PAGE_SIZE - 1); /* @@ -590,13 +590,17 @@ static int hvmemul_insn_fetch( container_of(ctxt, struct hvm_emulate_ctxt, ctxt); unsigned int insn_off = offset - hvmemul_ctxt->insn_buf_eip; - /* Fall back if requested bytes are not in the prefetch cache. */ - if ( unlikely((insn_off + bytes) > hvmemul_ctxt->insn_buf_bytes) ) + /* + * Fall back if requested bytes are not in the prefetch cache. + * But always perform the (fake) read when bytes == 0. + */ + if ( !bytes || + unlikely((insn_off + bytes) > hvmemul_ctxt->insn_buf_bytes) ) { int rc = __hvmemul_read(seg, offset, p_data, bytes, hvm_access_insn_fetch, hvmemul_ctxt); - if ( rc == X86EMUL_OKAY ) + if ( rc == X86EMUL_OKAY && bytes ) { ASSERT(insn_off + bytes <= sizeof(hvmemul_ctxt->insn_buf)); memcpy(&hvmemul_ctxt->insn_buf[insn_off], p_data, bytes); @@ -630,7 +634,7 @@ static int hvmemul_write( rc = hvmemul_virtual_to_linear( seg, offset, bytes, &reps, hvm_access_write, hvmemul_ctxt, &addr); - if ( rc != X86EMUL_OKAY ) + if ( rc != X86EMUL_OKAY || !bytes ) return rc; off = addr & (PAGE_SIZE - 1); /* See the respective comment in __hvmemul_read(). */ --- a/xen/arch/x86/hvm/hvm.c +++ b/xen/arch/x86/hvm/hvm.c @@ -2139,7 +2139,7 @@ int hvm_virtual_to_linear_addr( * Certain of them are not done in native real mode anyway. */ addr = (uint32_t)(addr + reg->base); - last_byte = (uint32_t)addr + bytes - 1; + last_byte = (uint32_t)addr + bytes - !!bytes; if ( last_byte < addr ) return 0; } @@ -2163,7 +2163,7 @@ int hvm_virtual_to_linear_addr( break; } - last_byte = (uint32_t)offset + bytes - 1; + last_byte = (uint32_t)offset + bytes - !!bytes; /* Is this a grows-down data segment? Special limit check if so. */ if ( (reg->attr.fields.type & 0xc) == 0x4 ) @@ -2194,7 +2194,7 @@ int hvm_virtual_to_linear_addr( if ( (seg == x86_seg_fs) || (seg == x86_seg_gs) ) addr += reg->base; - last_byte = addr + bytes - 1; + last_byte = addr + bytes - !!bytes; if ( !is_canonical_address(addr) || last_byte < addr || !is_canonical_address(last_byte) ) return 0; --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -4944,10 +4944,11 @@ static int ptwr_emulated_read( unsigned int bytes, struct x86_emulate_ctxt *ctxt) { - unsigned int rc; + unsigned int rc = bytes; unsigned long addr = offset; - if ( (rc = copy_from_user(p_data, (void *)addr, bytes)) != 0 ) + if ( !__addr_ok(addr) || + (rc = __copy_from_user(p_data, (void *)addr, bytes)) ) { propagate_page_fault(addr + bytes - rc, 0); /* read fault */ return X86EMUL_EXCEPTION; @@ -5096,7 +5097,7 @@ static int ptwr_emulated_write( { paddr_t val = 0; - if ( (bytes > sizeof(paddr_t)) || (bytes & (bytes -1)) ) + if ( (bytes > sizeof(paddr_t)) || (bytes & (bytes - 1)) || !bytes ) { MEM_LOG("ptwr_emulate: bad write size (addr=%lx, bytes=%u)", offset, bytes); @@ -5226,7 +5227,8 @@ static int mmio_ro_emulated_write( container_of(ctxt, struct mmio_ro_emulate_ctxt, ctxt); /* Only allow naturally-aligned stores at the original %cr2 address. */ - if ( ((bytes | offset) & (bytes - 1)) || offset != mmio_ro_ctxt->cr2 ) + if ( ((bytes | offset) & (bytes - 1)) || !bytes || + offset != mmio_ro_ctxt->cr2 ) { MEM_LOG("mmio_ro_emulate: bad access (cr2=%lx, addr=%lx, bytes=%u)", mmio_ro_ctxt->cr2, offset, bytes); --- a/xen/arch/x86/mm/shadow/common.c +++ b/xen/arch/x86/mm/shadow/common.c @@ -155,7 +155,7 @@ hvm_read(enum x86_segment seg, rc = hvm_translate_linear_addr( seg, offset, bytes, access_type, sh_ctxt, &addr); - if ( rc ) + if ( rc || !bytes ) return rc; if ( access_type == hvm_access_insn_fetch ) @@ -239,7 +239,7 @@ hvm_emulate_write(enum x86_segment seg, rc = hvm_translate_linear_addr( seg, offset, bytes, hvm_access_write, sh_ctxt, &addr); - if ( rc ) + if ( rc || !bytes ) return rc; return v->arch.paging.mode->shadow.x86_emulate_write( --- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -647,14 +647,26 @@ do { #define jmp_rel(rel) \ do { \ - int _rel = (int)(rel); \ - _regs.eip += _rel; \ + unsigned long ip = _regs.eip + (int)(rel); \ if ( op_bytes == 2 ) \ - _regs.eip = (uint16_t)_regs.eip; \ + ip = (uint16_t)ip; \ else if ( !mode_64bit() ) \ - _regs.eip = (uint32_t)_regs.eip; \ + ip = (uint32_t)ip; \ + rc = ops->insn_fetch(x86_seg_cs, ip, NULL, 0, ctxt); \ + if ( rc ) goto done; \ + _regs.eip = ip; \ } while (0) +#define validate_far_branch(cs, ip) \ + generate_exception_if(in_longmode(ctxt, ops) && (cs)->attr.fields.l \ + ? !is_canonical_address(ip) \ + : (ip) > (cs)->limit, EXC_GP, 0) + +#define commit_far_branch(cs, ip) ({ \ + validate_far_branch(cs, ip); \ + ops->write_segment(x86_seg_cs, cs, ctxt); \ +}) + struct fpu_insn_ctxt { uint8_t insn_bytes; uint8_t exn_raised; @@ -1099,29 +1111,30 @@ static int realmode_load_seg( enum x86_segment seg, uint16_t sel, + struct segment_register *sreg, struct x86_emulate_ctxt *ctxt, const struct x86_emulate_ops *ops) { - struct segment_register reg; - int rc; + int rc = ops->read_segment(seg, sreg, ctxt); - if ( (rc = ops->read_segment(seg, ®, ctxt)) != 0 ) - return rc; - - reg.sel = sel; - reg.base = (uint32_t)sel << 4; + if ( !rc ) + { + sreg->sel = sel; + sreg->base = (uint32_t)sel << 4; + } - return ops->write_segment(seg, ®, ctxt); + return rc; } static int protmode_load_seg( enum x86_segment seg, uint16_t sel, bool_t is_ret, + struct segment_register *sreg, struct x86_emulate_ctxt *ctxt, const struct x86_emulate_ops *ops) { - struct segment_register desctab, ss, segr; + struct segment_register desctab, ss; struct { uint32_t a, b; } desc; uint8_t dpl, rpl, cpl; uint32_t new_desc_b, a_flag = 0x100; @@ -1132,8 +1145,8 @@ protmode_load_seg( { if ( (seg == x86_seg_cs) || (seg == x86_seg_ss) ) goto raise_exn; - memset(&segr, 0, sizeof(segr)); - return ops->write_segment(seg, &segr, ctxt); + memset(sreg, 0, sizeof(*sreg)); + return X86EMUL_OKAY; } /* System segment descriptors must reside in the GDT. */ @@ -1242,16 +1255,16 @@ protmode_load_seg( desc.b |= a_flag; skip_accessed_flag: - segr.base = (((desc.b << 0) & 0xff000000u) | - ((desc.b << 16) & 0x00ff0000u) | - ((desc.a >> 16) & 0x0000ffffu)); - segr.attr.bytes = (((desc.b >> 8) & 0x00ffu) | - ((desc.b >> 12) & 0x0f00u)); - segr.limit = (desc.b & 0x000f0000u) | (desc.a & 0x0000ffffu); - if ( segr.attr.fields.g ) - segr.limit = (segr.limit << 12) | 0xfffu; - segr.sel = sel; - return ops->write_segment(seg, &segr, ctxt); + sreg->base = (((desc.b << 0) & 0xff000000u) | + ((desc.b << 16) & 0x00ff0000u) | + ((desc.a >> 16) & 0x0000ffffu)); + sreg->attr.bytes = (((desc.b >> 8) & 0x00ffu) | + ((desc.b >> 12) & 0x0f00u)); + sreg->limit = (desc.b & 0x000f0000u) | (desc.a & 0x0000ffffu); + if ( sreg->attr.fields.g ) + sreg->limit = (sreg->limit << 12) | 0xfffu; + sreg->sel = sel; + return X86EMUL_OKAY; raise_exn: if ( ops->inject_hw_exception == NULL ) @@ -1265,17 +1278,29 @@ static int load_seg( enum x86_segment seg, uint16_t sel, bool_t is_ret, + struct segment_register *sreg, struct x86_emulate_ctxt *ctxt, const struct x86_emulate_ops *ops) { + struct segment_register reg; + int rc; + if ( (ops->read_segment == NULL) || (ops->write_segment == NULL) ) return X86EMUL_UNHANDLEABLE; + if ( !sreg ) + sreg = ® + if ( in_protmode(ctxt, ops) ) - return protmode_load_seg(seg, sel, is_ret, ctxt, ops); + rc = protmode_load_seg(seg, sel, is_ret, sreg, ctxt, ops); + else + rc = realmode_load_seg(seg, sel, sreg, ctxt, ops); + + if ( !rc && sreg == ® ) + rc = ops->write_segment(seg, sreg, ctxt); - return realmode_load_seg(seg, sel, ctxt, ops); + return rc; } void * @@ -1849,6 +1874,8 @@ x86_emulate( switch ( b ) { + struct segment_register cs; + case 0x00 ... 0x05: add: /* add */ emulate_2op_SrcV("add", src, dst, _regs.eflags); break; @@ -1910,7 +1937,7 @@ x86_emulate( if ( (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes), &dst.val, op_bytes, ctxt, ops)) != 0 ) goto done; - if ( (rc = load_seg(src.val, dst.val, 0, ctxt, ops)) != 0 ) + if ( (rc = load_seg(src.val, dst.val, 0, NULL, ctxt, ops)) != 0 ) return rc; break; @@ -2264,7 +2291,7 @@ x86_emulate( enum x86_segment seg = decode_segment(modrm_reg); generate_exception_if(seg == decode_segment_failed, EXC_UD, -1); generate_exception_if(seg == x86_seg_cs, EXC_UD, -1); - if ( (rc = load_seg(seg, src.val, 0, ctxt, ops)) != 0 ) + if ( (rc = load_seg(seg, src.val, 0, NULL, ctxt, ops)) != 0 ) goto done; if ( seg == x86_seg_ss ) ctxt->retire.flags.mov_ss = 1; @@ -2339,14 +2366,15 @@ x86_emulate( sel = insn_fetch_type(uint16_t); if ( (rc = ops->read_segment(x86_seg_cs, ®, ctxt)) || - (rc = ops->write(x86_seg_ss, sp_pre_dec(op_bytes), + (rc = load_seg(x86_seg_cs, sel, 0, &cs, ctxt, ops)) || + (validate_far_branch(&cs, eip), + rc = ops->write(x86_seg_ss, sp_pre_dec(op_bytes), ®.sel, op_bytes, ctxt)) || (rc = ops->write(x86_seg_ss, sp_pre_dec(op_bytes), - &_regs.eip, op_bytes, ctxt)) ) + &_regs.eip, op_bytes, ctxt)) || + (rc = ops->write_segment(x86_seg_cs, &cs, ctxt)) ) goto done; - if ( (rc = load_seg(x86_seg_cs, sel, 0, ctxt, ops)) != 0 ) - goto done; _regs.eip = eip; break; } @@ -2554,7 +2582,8 @@ x86_emulate( int offset = (b == 0xc2) ? insn_fetch_type(uint16_t) : 0; op_bytes = ((op_bytes == 4) && mode_64bit()) ? 8 : op_bytes; if ( (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes + offset), - &dst.val, op_bytes, ctxt, ops)) != 0 ) + &dst.val, op_bytes, ctxt, ops)) != 0 || + (rc = ops->insn_fetch(x86_seg_cs, dst.val, NULL, 0, ctxt)) ) goto done; _regs.eip = dst.val; break; @@ -2569,7 +2598,7 @@ x86_emulate( if ( (rc = read_ulong(src.mem.seg, src.mem.off + src.bytes, &sel, 2, ctxt, ops)) != 0 ) goto done; - if ( (rc = load_seg(dst.val, sel, 0, ctxt, ops)) != 0 ) + if ( (rc = load_seg(dst.val, sel, 0, NULL, ctxt, ops)) != 0 ) goto done; dst.val = src.val; break; @@ -2643,7 +2672,8 @@ x86_emulate( &dst.val, op_bytes, ctxt, ops)) || (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes + offset), &src.val, op_bytes, ctxt, ops)) || - (rc = load_seg(x86_seg_cs, src.val, 1, ctxt, ops)) ) + (rc = load_seg(x86_seg_cs, src.val, 1, &cs, ctxt, ops)) || + (rc = commit_far_branch(&cs, dst.val)) ) goto done; _regs.eip = dst.val; break; @@ -2670,7 +2700,7 @@ x86_emulate( goto swint; case 0xcf: /* iret */ { - unsigned long cs, eip, eflags; + unsigned long sel, eip, eflags; uint32_t mask = EFLG_VIP | EFLG_VIF | EFLG_VM; if ( !mode_ring0() ) mask |= EFLG_IOPL; @@ -2680,7 +2710,7 @@ x86_emulate( if ( (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes), &eip, op_bytes, ctxt, ops)) || (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes), - &cs, op_bytes, ctxt, ops)) || + &sel, op_bytes, ctxt, ops)) || (rc = read_ulong(x86_seg_ss, sp_post_inc(op_bytes), &eflags, op_bytes, ctxt, ops)) ) goto done; @@ -2690,7 +2720,8 @@ x86_emulate( _regs.eflags &= mask; _regs.eflags |= (uint32_t)(eflags & ~mask) | 0x02; _regs.eip = eip; - if ( (rc = load_seg(x86_seg_cs, cs, 1, ctxt, ops)) != 0 ) + if ( (rc = load_seg(x86_seg_cs, sel, 1, &cs, ctxt, ops)) || + (rc = commit_far_branch(&cs, eip)) ) goto done; break; } @@ -3320,7 +3351,8 @@ x86_emulate( generate_exception_if(mode_64bit(), EXC_UD, -1); eip = insn_fetch_bytes(op_bytes); sel = insn_fetch_type(uint16_t); - if ( (rc = load_seg(x86_seg_cs, sel, 0, ctxt, ops)) != 0 ) + if ( (rc = load_seg(x86_seg_cs, sel, 0, &cs, ctxt, ops)) || + (rc = commit_far_branch(&cs, eip)) ) goto done; _regs.eip = eip; break; @@ -3589,10 +3621,14 @@ x86_emulate( break; case 2: /* call (near) */ dst.val = _regs.eip; + if ( (rc = ops->insn_fetch(x86_seg_cs, src.val, NULL, 0, ctxt)) ) + goto done; _regs.eip = src.val; src.val = dst.val; goto push; case 4: /* jmp (near) */ + if ( (rc = ops->insn_fetch(x86_seg_cs, src.val, NULL, 0, ctxt)) ) + goto done; _regs.eip = src.val; dst.type = OP_NONE; break; @@ -3611,14 +3647,17 @@ x86_emulate( struct segment_register reg; fail_if(ops->read_segment == NULL); if ( (rc = ops->read_segment(x86_seg_cs, ®, ctxt)) || - (rc = ops->write(x86_seg_ss, sp_pre_dec(op_bytes), + (rc = load_seg(x86_seg_cs, sel, 0, &cs, ctxt, ops)) || + (validate_far_branch(&cs, src.val), + rc = ops->write(x86_seg_ss, sp_pre_dec(op_bytes), ®.sel, op_bytes, ctxt)) || (rc = ops->write(x86_seg_ss, sp_pre_dec(op_bytes), - &_regs.eip, op_bytes, ctxt)) ) + &_regs.eip, op_bytes, ctxt)) || + (rc = ops->write_segment(x86_seg_cs, &cs, ctxt)) ) goto done; } - - if ( (rc = load_seg(x86_seg_cs, sel, 0, ctxt, ops)) != 0 ) + else if ( (rc = load_seg(x86_seg_cs, sel, 0, &cs, ctxt, ops)) || + (rc = commit_far_branch(&cs, src.val)) ) goto done; _regs.eip = src.val; @@ -3700,7 +3739,7 @@ x86_emulate( generate_exception_if(!in_protmode(ctxt, ops), EXC_UD, -1); generate_exception_if(!mode_ring0(), EXC_GP, 0); if ( (rc = load_seg((modrm_reg & 1) ? x86_seg_tr : x86_seg_ldtr, - src.val, 0, ctxt, ops)) != 0 ) + src.val, 0, NULL, ctxt, ops)) != 0 ) goto done; break; @@ -4104,6 +4143,9 @@ x86_emulate( goto done; generate_exception_if(!(msr_content & 0xfffc), EXC_GP, 0); + generate_exception_if(user64 && (!is_canonical_address(_regs.edx) || + !is_canonical_address(_regs.ecx)), + EXC_GP, 0); cs.sel = (msr_content | 3) + /* SELECTOR_RPL_MASK */ (user64 ? 32 : 16);
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