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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen stable-4.2] x86: limit checks in hypercall_xlat_continuation() to actual arguments
commit 7d80d71da3369ddfed5ec4cb822194cfd0faf23e
Author: Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Nov 27 14:17:32 2014 +0100
Commit: Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Nov 27 14:17:32 2014 +0100
x86: limit checks in hypercall_xlat_continuation() to actual arguments
HVM/PVH guests can otherwise trigger the final BUG_ON() in that
function by entering 64-bit mode, setting the high halves of affected
registers to non-zero values, leaving 64-bit mode, and issuing a
hypercall that might get preempted and hence become subject to
continuation argument translation (HYPERVISOR_memory_op being the only
one possible for HVM, PVH also having the option of using
HYPERVISOR_mmuext_op). This issue got introduced when HVM code was
switched to use compat_memory_op() - neither that nor
hypercall_xlat_continuation() were originally intended to be used by
other than PV guests (which can't enter 64-bit mode and hence have no
way to alter the high halves of 64-bit registers).
This is CVE-2014-8866 / XSA-111.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Tim Deegan <tim@xxxxxxx>
---
xen/arch/x86/domain.c | 12 ++++++++----
xen/arch/x86/x86_64/compat/mm.c | 8 ++++----
xen/common/compat/memory.c | 2 +-
xen/include/xen/compat.h | 5 ++++-
4 files changed, 17 insertions(+), 10 deletions(-)
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 2799e86..8599655 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1921,7 +1921,8 @@ unsigned long hypercall_create_continuation(
}
#ifdef CONFIG_COMPAT
-int hypercall_xlat_continuation(unsigned int *id, unsigned int mask, ...)
+int hypercall_xlat_continuation(unsigned int *id, unsigned int nr,
+ unsigned int mask, ...)
{
int rc = 0;
struct mc_state *mcs = ¤t->mc_state;
@@ -1930,7 +1931,10 @@ int hypercall_xlat_continuation(unsigned int *id,
unsigned int mask, ...)
unsigned long nval = 0;
va_list args;
- BUG_ON(id && *id > 5);
+ ASSERT(nr <= ARRAY_SIZE(mcs->call.args));
+ ASSERT(!(mask >> nr));
+
+ BUG_ON(id && *id >= nr);
BUG_ON(id && (mask & (1U << *id)));
va_start(args, mask);
@@ -1939,7 +1943,7 @@ int hypercall_xlat_continuation(unsigned int *id,
unsigned int mask, ...)
{
if ( !test_bit(_MCSF_call_preempted, &mcs->flags) )
return 0;
- for ( i = 0; i < 6; ++i, mask >>= 1 )
+ for ( i = 0; i < nr; ++i, mask >>= 1 )
{
if ( mask & 1 )
{
@@ -1967,7 +1971,7 @@ int hypercall_xlat_continuation(unsigned int *id,
unsigned int mask, ...)
else
{
regs = guest_cpu_user_regs();
- for ( i = 0; i < 6; ++i, mask >>= 1 )
+ for ( i = 0; i < nr; ++i, mask >>= 1 )
{
unsigned long *reg;
diff --git a/xen/arch/x86/x86_64/compat/mm.c b/xen/arch/x86/x86_64/compat/mm.c
index ef7822b..8cf3c3a 100644
--- a/xen/arch/x86/x86_64/compat/mm.c
+++ b/xen/arch/x86/x86_64/compat/mm.c
@@ -78,7 +78,7 @@ int compat_arch_memory_op(int op, XEN_GUEST_HANDLE(void) arg)
}
if ( rc == __HYPERVISOR_memory_op )
- hypercall_xlat_continuation(NULL, 0x2, nat, arg);
+ hypercall_xlat_continuation(NULL, 2, 0x2, nat, arg);
break;
}
@@ -144,7 +144,7 @@ int compat_arch_memory_op(int op, XEN_GUEST_HANDLE(void)
arg)
break;
if ( rc == __HYPERVISOR_memory_op )
- hypercall_xlat_continuation(NULL, 0x2, nat, arg);
+ hypercall_xlat_continuation(NULL, 2, 0x2, nat, arg);
XLAT_pod_target(&cmp, nat);
@@ -379,7 +379,7 @@ int compat_mmuext_op(XEN_GUEST_HANDLE(mmuext_op_compat_t)
cmp_uops,
left = 1;
if ( arg1 != MMU_UPDATE_PREEMPTED )
{
- BUG_ON(!hypercall_xlat_continuation(&left, 0x01, nat_ops,
+ BUG_ON(!hypercall_xlat_continuation(&left, 4, 0x01,
nat_ops,
cmp_uops));
if ( !test_bit(_MCSF_in_multicall, &mcs->flags) )
regs->_ecx += count - i;
@@ -387,7 +387,7 @@ int compat_mmuext_op(XEN_GUEST_HANDLE(mmuext_op_compat_t)
cmp_uops,
mcs->compat_call.args[1] += count - i;
}
else
- BUG_ON(hypercall_xlat_continuation(&left, 0));
+ BUG_ON(hypercall_xlat_continuation(&left, 4, 0));
BUG_ON(left != arg1);
}
else
diff --git a/xen/common/compat/memory.c b/xen/common/compat/memory.c
index 2355cb9..3c8b97d 100644
--- a/xen/common/compat/memory.c
+++ b/xen/common/compat/memory.c
@@ -208,7 +208,7 @@ int compat_memory_op(unsigned int cmd,
XEN_GUEST_HANDLE(void) compat)
break;
cmd = 0;
- if ( hypercall_xlat_continuation(&cmd, 0x02, nat.hnd, compat) )
+ if ( hypercall_xlat_continuation(&cmd, 2, 0x02, nat.hnd, compat) )
{
BUG_ON(rc != __HYPERVISOR_memory_op);
BUG_ON((cmd & MEMOP_CMD_MASK) != op);
diff --git a/xen/include/xen/compat.h b/xen/include/xen/compat.h
index 857cbc7..4f6af70 100644
--- a/xen/include/xen/compat.h
+++ b/xen/include/xen/compat.h
@@ -192,6 +192,8 @@ static inline int name(k xen_ ## n *x, k compat_ ## n *c) \
* This option is useful for extracting the "op" argument or similar from the
* hypercall to enable further xlat processing.
*
+ * nr: Total number of arguments the hypercall has.
+ *
* mask: Specifies which of the hypercall arguments require compat translation.
* bit 0 indicates that the 0'th argument requires translation, bit 1 indicates
* that the first argument requires translation and so on. Native and compat
@@ -211,7 +213,8 @@ static inline int name(k xen_ ## n *x, k compat_ ## n *c) \
*
* Return: Number of arguments which were actually translated.
*/
-int hypercall_xlat_continuation(unsigned int *id, unsigned int mask, ...);
+int hypercall_xlat_continuation(unsigned int *id, unsigned int nr,
+ unsigned int mask, ...);
/* In-place translation functons: */
struct start_info;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.2
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