[patch] xsa183-unstable.patch

xsa183-unstable.patch (text/plain), 2.21 KB, created by Aaron Bauman (RETIRED) on 2016-07-13 19:41:11 UTC

From afbbdd41edcdaf1b575d976aed493ac449727154 Mon Sep 17 00:00:00 2001
From: Andrew Cooper <[e-mail]>
Date: Wed, 15 Jun 2016 18:32:14 +0100
Subject: [PATCH] x86/entry: Avoid SMAP violation in
 compat_create_bounce_frame()

A 32bit guest kernel might be running on user mappings.
compat_create_bounce_frame() must whitelist its guest accesses to avoid
risking a SMAP violation.

For both variants of create_bounce_frame(), re-blacklist user accesses if
execution exits via an exception table redirection.

This is XSA-183

Signed-off-by: Andrew Cooper <[e-mail]>
Reviewed-by: George Dunlap <[e-mail]>
---
 xen/arch/x86/x86_64/compat/entry.S | 3 +++
 xen/arch/x86/x86_64/entry.S        | 1 +
 2 files changed, 4 insertions(+)

diff --git a/xen/arch/x86/x86_64/compat/entry.S b/xen/arch/x86/x86_64/compat/entry.S
index 7f02afd..d9cfc17 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -319,6 +319,7 @@ compat_create_bounce_frame:
         ASSERT_INTERRUPTS_ENABLED
         mov   %fs,%edi
         testb $2,UREGS_cs+8(%rsp)
+        ASM_STAC
         jz    1f
         /* Push new frame at registered guest-OS stack base. */
         movl  VCPU_kernel_sp(%rbx),%esi
@@ -364,6 +365,7 @@ compat_create_bounce_frame:
         movl  TRAPBOUNCE_error_code(%rdx),%eax
 .Lft8:  movl  %eax,%fs:(%rsi)           # ERROR CODE
 1:
+        ASM_CLAC
         /* Rewrite our stack frame and return to guest-OS mode. */
         /* IA32 Ref. Vol. 3: TF, VM, RF and NT flags are cleared on trap. */
         andl  $~(X86_EFLAGS_VM|X86_EFLAGS_RF|\
@@ -403,6 +405,7 @@ compat_crash_page_fault_4:
         addl  $4,%esi
 compat_crash_page_fault:
 .Lft14: mov   %edi,%fs
+        ASM_CLAC
         movl  %esi,%edi
         call  show_page_walk
         jmp   dom_crash_sync_extable
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index ad8c64c..88adb2d 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -420,6 +420,7 @@ domain_crash_page_fault_16:
 domain_crash_page_fault_8:
         addq  $8,%rsi
 domain_crash_page_fault:
+        ASM_CLAC
         movq  %rsi,%rdi
         call  show_page_walk
 ENTRY(dom_crash_sync_extable)
-- 
2.1.4