From: Jan Beulich Date: Fri, 22 May 2015 08:50:14 +0000 (+0200) Subject: x86: switch default mapping attributes to non-executable X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~3167 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=abcf15fa8f8b6e22430a364391d5d4ca20de999f;p=xen.git x86: switch default mapping attributes to non-executable Only a very limited subset of mappings need to be done as executable ones; in particular the direct mapping should not be executable to limit the damage attackers can cause by exploiting security relevant bugs. The EFI change at once includes an adjustment to set NX only when supported by the hardware. Signed-off-by: Jan Beulich Reviewed-by: Andrew Cooper --- diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c index 6e9464c77b..db073a61d1 100644 --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -293,7 +293,7 @@ struct vcpu_guest_context *alloc_vcpu_guest_context(void) free_vcpu_guest_context(NULL); return NULL; } - __set_fixmap(idx - i, page_to_mfn(pg), __PAGE_HYPERVISOR); + __set_fixmap(idx - i, page_to_mfn(pg), __PAGE_HYPERVISOR_RW); per_cpu(vgc_pages[i], cpu) = pg; } return (void *)fix_to_virt(idx); diff --git a/xen/arch/x86/domain_page.c b/xen/arch/x86/domain_page.c index 158a1645d7..5f6f3974c3 100644 --- a/xen/arch/x86/domain_page.c +++ b/xen/arch/x86/domain_page.c @@ -160,7 +160,7 @@ void *map_domain_page(unsigned long mfn) spin_unlock(&dcache->lock); - l1e_write(&MAPCACHE_L1ENT(idx), l1e_from_pfn(mfn, __PAGE_HYPERVISOR)); + l1e_write(&MAPCACHE_L1ENT(idx), l1e_from_pfn(mfn, __PAGE_HYPERVISOR_RW)); out: local_irq_restore(flags); diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index 74e146d027..7a7a85402d 100644 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -4412,7 +4412,7 @@ long set_gdt(struct vcpu *v, for ( i = 0; i < nr_pages; i++ ) { v->arch.pv_vcpu.gdt_frames[i] = frames[i]; - l1e_write(&pl1e[i], l1e_from_pfn(frames[i], __PAGE_HYPERVISOR)); + l1e_write(&pl1e[i], l1e_from_pfn(frames[i], __PAGE_HYPERVISOR_RW)); } xfree(pfns); @@ -6003,7 +6003,7 @@ int create_perdomain_mapping(struct domain *d, unsigned long va, if ( !IS_NIL(ppg) ) *ppg++ = pg; l1tab[l1_table_offset(va)] = - l1e_from_page(pg, __PAGE_HYPERVISOR | _PAGE_AVAIL0); + l1e_from_page(pg, __PAGE_HYPERVISOR_RW | _PAGE_AVAIL0); l2e_add_flags(*pl2e, _PAGE_AVAIL0); } else @@ -6132,7 +6132,7 @@ void memguard_init(void) (unsigned long)__va(start), start >> PAGE_SHIFT, (__pa(&_end) + PAGE_SIZE - 1 - start) >> PAGE_SHIFT, - __PAGE_HYPERVISOR|MAP_SMALL_PAGES); + __PAGE_HYPERVISOR_RW|MAP_SMALL_PAGES); BUG_ON(start != xen_phys_start); map_pages_to_xen( XEN_VIRT_START, @@ -6145,7 +6145,7 @@ static void __memguard_change_range(void *p, unsigned long l, int guard) { unsigned long _p = (unsigned long)p; unsigned long _l = (unsigned long)l; - unsigned int flags = __PAGE_HYPERVISOR | MAP_SMALL_PAGES; + unsigned int flags = __PAGE_HYPERVISOR_RW | MAP_SMALL_PAGES; /* Ensure we are dealing with a page-aligned whole number of pages. */ ASSERT((_p&~PAGE_MASK) == 0); diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c index e808ea905f..8e21859bf2 100644 --- a/xen/arch/x86/setup.c +++ b/xen/arch/x86/setup.c @@ -901,7 +901,7 @@ void __init noreturn __start_xen(unsigned long mbi_p) /* The only data mappings to be relocated are in the Xen area. */ pl2e = __va(__pa(l2_xenmap)); *pl2e++ = l2e_from_pfn(xen_phys_start >> PAGE_SHIFT, - PAGE_HYPERVISOR | _PAGE_PSE); + PAGE_HYPERVISOR_RWX | _PAGE_PSE); for ( i = 1; i < L2_PAGETABLE_ENTRIES; i++, pl2e++ ) { if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) ) @@ -1088,7 +1088,7 @@ void __init noreturn __start_xen(unsigned long mbi_p) /* This range must not be passed to the boot allocator and * must also not be mapped with _PAGE_GLOBAL. */ map_pages_to_xen((unsigned long)__va(map_e), PFN_DOWN(map_e), - PFN_DOWN(e - map_e), __PAGE_HYPERVISOR); + PFN_DOWN(e - map_e), __PAGE_HYPERVISOR_RW); } if ( s < map_s ) { @@ -1424,6 +1424,10 @@ void __init noreturn __start_xen(unsigned long mbi_p) if ( cpu_has_smap ) write_cr4(read_cr4() & ~X86_CR4_SMAP); + printk("%sNX (Execute Disable) protection %sactive\n", + cpu_has_nx ? XENLOG_INFO : XENLOG_WARNING "Warning: ", + cpu_has_nx ? "" : "not "); + /* * We're going to setup domain0 using the module(s) that we stashed safely * above our heap. The second module, if present, is an initrd ramdisk. diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c index a771a014fd..e58de58bec 100644 --- a/xen/arch/x86/x86_64/mm.c +++ b/xen/arch/x86/x86_64/mm.c @@ -895,6 +895,33 @@ void __init subarch_init_memory(void) share_xen_page_with_privileged_guests(page, XENSHARE_readonly); } } + + /* Mark low 16Mb of direct map NX if hardware supports it. */ + if ( !cpu_has_nx ) + return; + + v = DIRECTMAP_VIRT_START + (1UL << 20); + l3e = l4e_to_l3e(idle_pg_table[l4_table_offset(v)])[l3_table_offset(v)]; + ASSERT(l3e_get_flags(l3e) & _PAGE_PRESENT); + do { + l2e = l3e_to_l2e(l3e)[l2_table_offset(v)]; + ASSERT(l2e_get_flags(l2e) & _PAGE_PRESENT); + if ( l2e_get_flags(l2e) & _PAGE_PSE ) + { + l2e_add_flags(l2e, _PAGE_NX_BIT); + l3e_to_l2e(l3e)[l2_table_offset(v)] = l2e; + v += 1 << L2_PAGETABLE_SHIFT; + } + else + { + l1_pgentry_t l1e = l2e_to_l1e(l2e)[l1_table_offset(v)]; + + ASSERT(l1e_get_flags(l1e) & _PAGE_PRESENT); + l1e_add_flags(l1e, _PAGE_NX_BIT); + l2e_to_l1e(l2e)[l1_table_offset(v)] = l1e; + v += 1 << L1_PAGETABLE_SHIFT; + } + } while ( v < DIRECTMAP_VIRT_START + (16UL << 20) ); } long subarch_memory_op(unsigned long cmd, XEN_GUEST_HANDLE_PARAM(void) arg) @@ -1359,7 +1386,7 @@ int memory_add(unsigned long spfn, unsigned long epfn, unsigned int pxm) if ( i < spfn ) i = spfn; ret = map_pages_to_xen((unsigned long)mfn_to_virt(i), i, - epfn - i, __PAGE_HYPERVISOR); + epfn - i, __PAGE_HYPERVISOR_RW); if ( ret ) return ret; } diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c index f5e179beac..ef8476c676 100644 --- a/xen/common/efi/boot.c +++ b/xen/common/efi/boot.c @@ -1162,7 +1162,7 @@ void __init efi_init_memory(void) EFI_MEMORY_DESCRIPTOR *desc = efi_memmap + i; u64 len = desc->NumberOfPages << EFI_PAGE_SHIFT; unsigned long smfn, emfn; - unsigned int prot = PAGE_HYPERVISOR; + unsigned int prot = PAGE_HYPERVISOR_RWX; printk(XENLOG_INFO " %013" PRIx64 "-%013" PRIx64 " type=%u attr=%016" PRIx64 "\n", @@ -1195,7 +1195,7 @@ void __init efi_init_memory(void) if ( desc->Attribute & EFI_MEMORY_WP ) prot &= _PAGE_RW; if ( desc->Attribute & EFI_MEMORY_XP ) - prot |= _PAGE_NX_BIT; + prot |= _PAGE_NX; if ( pfn_to_pdx(emfn - 1) < (DIRECTMAP_SIZE >> PAGE_SHIFT) && !(smfn & pfn_hole_mask) && diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h index ef1e86fb1c..e26daafc8b 100644 --- a/xen/include/asm-x86/page.h +++ b/xen/include/asm-x86/page.h @@ -306,7 +306,8 @@ void efi_update_l4_pgtable(unsigned int l4idx, l4_pgentry_t); #define _PAGE_AVAIL1 _AC(0x400,U) #define _PAGE_AVAIL2 _AC(0x800,U) #define _PAGE_AVAIL _AC(0xE00,U) -#define _PAGE_PSE_PAT _AC(0x1000,U) +#define _PAGE_PSE_PAT _AC(0x1000,U) +#define _PAGE_NX (cpu_has_nx ? _PAGE_NX_BIT : 0) /* non-architectural flags */ #define _PAGE_PAGED 0x2000U #define _PAGE_SHARED 0x4000U @@ -323,6 +324,9 @@ void efi_update_l4_pgtable(unsigned int l4idx, l4_pgentry_t); #define _PAGE_GNTTAB 0 #endif +#define __PAGE_HYPERVISOR_RO (_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_NX) +#define __PAGE_HYPERVISOR_RW (__PAGE_HYPERVISOR_RO | \ + _PAGE_DIRTY | _PAGE_RW) #define __PAGE_HYPERVISOR_RX (_PAGE_PRESENT | _PAGE_ACCESSED) #define __PAGE_HYPERVISOR (__PAGE_HYPERVISOR_RX | \ _PAGE_DIRTY | _PAGE_RW) diff --git a/xen/include/asm-x86/x86_64/page.h b/xen/include/asm-x86/x86_64/page.h index fd2f700ee8..19ab4d05b4 100644 --- a/xen/include/asm-x86/x86_64/page.h +++ b/xen/include/asm-x86/x86_64/page.h @@ -147,9 +147,20 @@ typedef l4_pgentry_t root_pgentry_t; */ #define _PAGE_GUEST_KERNEL (1U<<12) -#define PAGE_HYPERVISOR (__PAGE_HYPERVISOR | _PAGE_GLOBAL) +#define PAGE_HYPERVISOR_RO (__PAGE_HYPERVISOR_RO | _PAGE_GLOBAL) +#define PAGE_HYPERVISOR_RW (__PAGE_HYPERVISOR_RW | _PAGE_GLOBAL) #define PAGE_HYPERVISOR_RX (__PAGE_HYPERVISOR_RX | _PAGE_GLOBAL) -#define PAGE_HYPERVISOR_NOCACHE (__PAGE_HYPERVISOR_NOCACHE | _PAGE_GLOBAL) +#define PAGE_HYPERVISOR_RWX (__PAGE_HYPERVISOR | _PAGE_GLOBAL) + +#ifdef __ASSEMBLY__ +/* Dependency on NX being available can't be expressed. */ +# define PAGE_HYPERVISOR PAGE_HYPERVISOR_RWX +# define PAGE_HYPERVISOR_NOCACHE (__PAGE_HYPERVISOR_NOCACHE | _PAGE_GLOBAL) +#else +# define PAGE_HYPERVISOR PAGE_HYPERVISOR_RW +# define PAGE_HYPERVISOR_NOCACHE (__PAGE_HYPERVISOR_NOCACHE | \ + _PAGE_GLOBAL | _PAGE_NX) +#endif #endif /* __X86_64_PAGE_H__ */