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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 4/4] 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 <jbeulich@xxxxxxxx>
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -293,7 +293,7 @@ struct vcpu_guest_context *alloc_vcpu_gu
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);
--- 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);
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -4416,7 +4416,7 @@ 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);
@@ -6004,7 +6004,7 @@ int create_perdomain_mapping(struct doma
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
@@ -6133,7 +6133,7 @@ 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,
@@ -6146,7 +6146,7 @@ static void __memguard_change_range(void
{
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);
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -900,7 +900,7 @@ void __init noreturn __start_xen(unsigne
/* 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) )
@@ -1087,7 +1087,7 @@ void __init noreturn __start_xen(unsigne
/* 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 )
{
--- 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, unsig
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;
}
--- 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) &&
--- a/xen/include/asm-x86/page.h
+++ b/xen/include/asm-x86/page.h
@@ -303,7 +303,8 @@ void paging_init(void);
#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
@@ -320,6 +321,9 @@ void paging_init(void);
#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)
--- 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__ */
Attachment:
x86-map-noexec.patch _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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