From 40d66baa46ca8a9ffa6df3e063a967d08ec92bcf Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 11 Oct 2013 09:28:26 +0200 Subject: x86: correct LDT checks - MMUEXT_SET_LDT should behave as similarly to the LLDT instruction as possible: fail only if the base address is non-canonical - instead LDT descriptor accesses should fault if the descriptor address ends up being non-canonical (by ensuring this we at once avoid reading an entry from the mach-to-phys table and consider it a page table entry) - fault propagation on using LDT selectors must distinguish #PF and #GP (the latter must be raised for a non-canonical descriptor address, which also applies to several other uses of propagate_page_fault(), and hence the problem is being fixed there) - map_ldt_shadow_page() should properly wrap addresses for 32-bit VMs At once remove the odd invokation of map_ldt_shadow_page() from the MMUEXT_SET_LDT handler: There's nothing really telling us that the first LDT page is going to be preferred over others. Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper Acked-by: Keir Fraser --- xen/arch/x86/domain.c | 20 ++++++-------------- xen/arch/x86/mm.c | 9 ++++----- xen/arch/x86/traps.c | 27 ++++++++++++++++++++++----- 3 files changed, 32 insertions(+), 24 deletions(-) (limited to 'xen/arch') diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c index 316ef0452e..52b7a37fec 100644 --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -674,12 +674,7 @@ int arch_set_info_guest( fixup_guest_code_selector(d, c.nat->trap_ctxt[i].cs); } - /* LDT safety checks. */ - if ( ((c.nat->ldt_base & (PAGE_SIZE-1)) != 0) || - (c.nat->ldt_ents > 8192) || - !array_access_ok(c.nat->ldt_base, - c.nat->ldt_ents, - LDT_ENTRY_SIZE) ) + if ( !__addr_ok(c.nat->ldt_base) ) return -EINVAL; } else @@ -692,15 +687,12 @@ int arch_set_info_guest( for ( i = 0; i < ARRAY_SIZE(c.cmp->trap_ctxt); i++ ) fixup_guest_code_selector(d, c.cmp->trap_ctxt[i].cs); - - /* LDT safety checks. */ - if ( ((c.cmp->ldt_base & (PAGE_SIZE-1)) != 0) || - (c.cmp->ldt_ents > 8192) || - !compat_array_access_ok(c.cmp->ldt_base, - c.cmp->ldt_ents, - LDT_ENTRY_SIZE) ) - return -EINVAL; } + + /* LDT safety checks. */ + if ( ((c(ldt_base) & (PAGE_SIZE - 1)) != 0) || + (c(ldt_ents) > 8192) ) + return -EINVAL; } v->fpu_initialised = !!(flags & VGCF_I387_VALID); diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index 7d4215dacc..43aacebe61 100644 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -582,6 +582,8 @@ int map_ldt_shadow_page(unsigned int off) BUG_ON(unlikely(in_irq())); + if ( is_pv_32bit_domain(d) ) + gva = (u32)gva; guest_get_eff_kern_l1e(v, gva, &l1e); if ( unlikely(!(l1e_get_flags(l1e) & _PAGE_PRESENT)) ) return 0; @@ -3229,9 +3231,8 @@ long do_mmuext_op( MEM_LOG("ignoring SET_LDT hypercall from external domain"); okay = 0; } - else if ( ((ptr & (PAGE_SIZE-1)) != 0) || - (ents > 8192) || - !array_access_ok(ptr, ents, LDT_ENTRY_SIZE) ) + else if ( ((ptr & (PAGE_SIZE - 1)) != 0) || !__addr_ok(ptr) || + (ents > 8192) ) { okay = 0; MEM_LOG("Bad args to SET_LDT: ptr=%lx, ents=%lx", ptr, ents); @@ -3244,8 +3245,6 @@ long do_mmuext_op( curr->arch.pv_vcpu.ldt_base = ptr; curr->arch.pv_vcpu.ldt_ents = ents; load_LDT(curr); - if ( ents != 0 ) - (void)map_ldt_shadow_page(0); } break; } diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c index 4a0950280f..35be017dc8 100644 --- a/xen/arch/x86/traps.c +++ b/xen/arch/x86/traps.c @@ -1065,12 +1065,24 @@ static void reserved_bit_page_fault( show_execution_state(regs); } -void propagate_page_fault(unsigned long addr, u16 error_code) +struct trap_bounce *propagate_page_fault(unsigned long addr, u16 error_code) { struct trap_info *ti; struct vcpu *v = current; struct trap_bounce *tb = &v->arch.pv_vcpu.trap_bounce; + if ( unlikely(!is_canonical_address(addr)) ) + { + ti = &v->arch.pv_vcpu.trap_ctxt[TRAP_gp_fault]; + tb->flags = TBF_EXCEPTION | TBF_EXCEPTION_ERRCODE; + tb->error_code = 0; + tb->cs = ti->cs; + tb->eip = ti->address; + if ( TI_GET_IF(ti) ) + tb->flags |= TBF_INTERRUPT; + return tb; + } + v->arch.pv_vcpu.ctrlreg[2] = addr; arch_set_cr2(v, addr); @@ -1097,6 +1109,8 @@ void propagate_page_fault(unsigned long addr, u16 error_code) if ( unlikely(error_code & PFEC_reserved_bit) ) reserved_bit_page_fault(addr, guest_cpu_user_regs()); + + return NULL; } static int handle_gdt_ldt_mapping_fault( @@ -1130,13 +1144,16 @@ static int handle_gdt_ldt_mapping_fault( } else { + struct trap_bounce *tb; + /* In hypervisor mode? Leave it to the #PF handler to fix up. */ if ( !guest_mode(regs) ) return 0; - /* In guest mode? Propagate #PF to guest, with adjusted %cr2. */ - propagate_page_fault( - curr->arch.pv_vcpu.ldt_base + offset, - regs->error_code); + /* In guest mode? Propagate fault to guest, with adjusted %cr2. */ + tb = propagate_page_fault(curr->arch.pv_vcpu.ldt_base + offset, + regs->error_code); + if ( tb ) + tb->error_code = ((u16)offset & ~3) | 4; } } else -- cgit v1.2.3