File xsa273-4.patch of Package xen.openSUSE_Leap_42.3_Update
x86/mm: Plumbing to allow any PTE update to fail with -ERESTART
Switching to shadow mode is performed in tasklet context. To facilitate this,
we schedule the tasklet, then create a hypercall continuation to allow the
switch to take place.
As a consequence, the x86 mm code needs to cope with an L1e operation being
continuable. do_mmu{,ext}_op() may no longer assert that a continuation
doesn't happen on the final iteration.
To handle the arguments correctly on continuation, compat_update_va_mapping*()
may no longer call into their non-compat counterparts. Move the compat
functions into mm.c rather than exporting __do_update_va_mapping() and
{get,put}_pg_owner(), and fix an unsigned long/int inconsistency with
compat_update_va_mapping_otherdomain().
This is part of XSA-273 / CVE-2018-3620.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -762,6 +762,9 @@ static int get_page_from_pagenr(unsigned
}
+static int __get_page_type(struct page_info *page, unsigned long type,
+ int preemptible);
+
static int get_page_and_type_from_pagenr(unsigned long page_nr,
unsigned long type,
struct domain *d,
@@ -775,9 +778,7 @@ static int get_page_and_type_from_pagenr
unlikely(!get_page_from_pagenr(page_nr, d)) )
return -EINVAL;
- rc = (preemptible ?
- get_page_type_preemptible(page, type) :
- (get_page_type(page, type) ? 0 : -EINVAL));
+ rc = __get_page_type(page, type, preemptible);
if ( unlikely(rc) && partial >= 0 &&
(!preemptible || page != current->arch.old_guest_table) )
@@ -1636,8 +1637,7 @@ static int create_pae_xen_mappings(struc
return 1;
}
-static int alloc_l2_table(struct page_info *page, unsigned long type,
- int preemptible)
+static int alloc_l2_table(struct page_info *page, unsigned long type)
{
struct domain *d = page_get_owner(page);
unsigned long pfn = page_to_mfn(page);
@@ -1649,8 +1649,7 @@ static int alloc_l2_table(struct page_in
for ( i = page->nr_validated_ptes; i < L2_PAGETABLE_ENTRIES; i++ )
{
- if ( preemptible && i > page->nr_validated_ptes
- && hypercall_preempt_check() )
+ if ( i > page->nr_validated_ptes && hypercall_preempt_check() )
{
page->nr_validated_ptes = i;
rc = -ERESTART;
@@ -1661,6 +1660,12 @@ static int alloc_l2_table(struct page_in
(rc = get_page_from_l2e(pl2e[i], pfn, d)) > 0 )
continue;
+ if ( unlikely(rc == -ERESTART) )
+ {
+ page->nr_validated_ptes = i;
+ break;
+ }
+
if ( rc < 0 )
{
gdprintk(XENLOG_WARNING, "Failure in alloc_l2_table: slot %#x\n", i);
@@ -1886,7 +1891,7 @@ static void free_l1_table(struct page_in
}
-static int free_l2_table(struct page_info *page, int preemptible)
+static int free_l2_table(struct page_info *page)
{
struct domain *d = page_get_owner(page);
unsigned long pfn = page_to_mfn(page);
@@ -1900,7 +1905,7 @@ static int free_l2_table(struct page_inf
do {
if ( is_guest_l2_slot(d, page->u.inuse.type_info, i) &&
put_page_from_l2e(pl2e[i], pfn) == 0 &&
- preemptible && i && hypercall_preempt_check() )
+ i && hypercall_preempt_check() )
{
page->nr_validated_ptes = i;
err = -ERESTART;
@@ -2510,7 +2515,8 @@ static int alloc_page_type(struct page_i
rc = alloc_l1_table(page);
break;
case PGT_l2_page_table:
- rc = alloc_l2_table(page, type, preemptible);
+ ASSERT(preemptible);
+ rc = alloc_l2_table(page, type);
break;
case PGT_l3_page_table:
ASSERT(preemptible);
@@ -2602,7 +2608,8 @@ int free_page_type(struct page_info *pag
rc = 0;
break;
case PGT_l2_page_table:
- rc = free_l2_table(page, preemptible);
+ ASSERT(preemptible);
+ rc = free_l2_table(page);
break;
case PGT_l3_page_table:
ASSERT(preemptible);
@@ -3901,12 +3908,9 @@ long do_mmuext_op(
}
if ( rc == -ERESTART )
- {
- ASSERT(i < count);
rc = hypercall_create_continuation(
__HYPERVISOR_mmuext_op, "hihi",
uops, (count - i) | MMU_UPDATE_PREEMPTED, pdone, foreigndom);
- }
else if ( curr->arch.old_guest_table )
{
XEN_GUEST_HANDLE_PARAM(void) null;
@@ -4197,12 +4201,9 @@ long do_mmu_update(
}
if ( rc == -ERESTART )
- {
- ASSERT(i < count);
rc = hypercall_create_continuation(
__HYPERVISOR_mmu_update, "hihi",
ureqs, (count - i) | MMU_UPDATE_PREEMPTED, pdone, foreigndom);
- }
else if ( curr->arch.old_guest_table )
{
XEN_GUEST_HANDLE_PARAM(void) null;
@@ -4927,7 +4928,13 @@ static int __do_update_va_mapping(
long do_update_va_mapping(unsigned long va, u64 val64,
unsigned long flags)
{
- return __do_update_va_mapping(va, val64, flags, current->domain);
+ int rc = __do_update_va_mapping(va, val64, flags, current->domain);
+
+ if ( rc == -ERESTART )
+ rc = hypercall_create_continuation(
+ __HYPERVISOR_update_va_mapping, "lll", va, val64, flags);
+
+ return rc;
}
long do_update_va_mapping_otherdomain(unsigned long va, u64 val64,
@@ -4944,6 +4951,46 @@ long do_update_va_mapping_otherdomain(un
put_pg_owner(pg_owner);
+ if ( rc == -ERESTART )
+ rc = hypercall_create_continuation(
+ __HYPERVISOR_update_va_mapping_otherdomain,
+ "llli", va, val64, flags, domid);
+
+ return rc;
+}
+
+int compat_update_va_mapping(unsigned int va, uint32_t lo, uint32_t hi,
+ unsigned int flags)
+{
+ int rc = __do_update_va_mapping(va, ((uint64_t)hi << 32) | lo,
+ flags, current->domain);
+
+ if ( rc == -ERESTART )
+ rc = hypercall_create_continuation(
+ __HYPERVISOR_update_va_mapping, "iiii", va, lo, hi, flags);
+
+ return rc;
+}
+
+int compat_update_va_mapping_otherdomain(unsigned int va,
+ uint32_t lo, uint32_t hi,
+ unsigned int flags, domid_t domid)
+{
+ struct domain *pg_owner;
+ int rc;
+
+ if ( (pg_owner = get_pg_owner(domid)) == NULL )
+ return -ESRCH;
+
+ rc = __do_update_va_mapping(va, ((uint64_t)hi << 32) | lo, flags, pg_owner);
+
+ put_pg_owner(pg_owner);
+
+ if ( rc == -ERESTART )
+ rc = hypercall_create_continuation(
+ __HYPERVISOR_update_va_mapping_otherdomain,
+ "iiiii", va, lo, hi, flags, domid);
+
return rc;
}
--- a/xen/arch/x86/x86_64/compat/mm.c
+++ b/xen/arch/x86/x86_64/compat/mm.c
@@ -200,19 +200,6 @@ int compat_arch_memory_op(unsigned long
return rc;
}
-int compat_update_va_mapping(unsigned int va, u32 lo, u32 hi,
- unsigned int flags)
-{
- return do_update_va_mapping(va, lo | ((u64)hi << 32), flags);
-}
-
-int compat_update_va_mapping_otherdomain(unsigned long va, u32 lo, u32 hi,
- unsigned long flags,
- domid_t domid)
-{
- return do_update_va_mapping_otherdomain(va, lo | ((u64)hi << 32), flags, domid);
-}
-
DEFINE_XEN_GUEST_HANDLE(mmuext_op_compat_t);
int compat_mmuext_op(XEN_GUEST_HANDLE_PARAM(void) arg,
--- a/xen/include/asm-x86/hypercall.h
+++ b/xen/include/asm-x86/hypercall.h
@@ -160,7 +160,7 @@ extern int compat_update_va_mapping(
unsigned int va, u32 lo, u32 hi, unsigned int flags);
extern int compat_update_va_mapping_otherdomain(
- unsigned long va, u32 lo, u32 hi, unsigned long flags, domid_t domid);
+ unsigned int va, u32 lo, u32 hi, unsigned int flags, domid_t domid);
DEFINE_XEN_GUEST_HANDLE(trap_info_compat_t);
extern int compat_set_trap_table(XEN_GUEST_HANDLE(trap_info_compat_t) traps);
