[PATCH] x86, boot: initialize __default_kernel_pte_mask in KASLR code

[Dave Hansen]

The somewhat discrete arch/x86/boot/compressed code shares headers with
the main kernel, but needs its own copies of some variables.  The copy
of __default_kernel_pte_mask did not get initialized correctly and has
been reported to cause boot failures when KASLR is in use by Tom
Lendacky and Mike Galibrath.

I've oddly been unable to reproduce these, but the fix is simple and
confirmed to work by Tom and Mike.

Signed-off-by: Dave Hansen 
Fixes: 64c80759408f ("x86/mm: Do not auto-massage page protections")
Cc: Tom Lendacky 
Cc: Mike Galbraith 
Cc: Andy Lutomirski 
Cc: Arjan van de Ven 
Cc: Borislav Petkov 
Cc: Dan Williams 
Cc: David Woodhouse 
Cc: Greg Kroah-Hartman 
Cc: Hugh Dickins 
Cc: Josh Poimboeuf 
Cc: Juergen Gross 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Nadav Amit 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux...@kvack.org
---

 b/arch/x86/boot/compressed/kaslr.c |4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN 
arch/x86/boot/compressed/kaslr.c~x86-boot-initialize-__default_kernel_pte_mask 
arch/x86/boot/compressed/kaslr.c
--- 
a/arch/x86/boot/compressed/kaslr.c~x86-boot-initialize-__default_kernel_pte_mask
2018-04-10 13:02:22.359914088 -0700
+++ b/arch/x86/boot/compressed/kaslr.c  2018-04-10 13:02:40.389914043 -0700
@@ -54,8 +54,8 @@ unsigned int ptrs_per_p4d __ro_after_ini
 
 extern unsigned long get_cmd_line_ptr(void);
 
-/* Used by PAGE_KERN* macros: */
-pteval_t __default_kernel_pte_mask __read_mostly;
+/* Used by PAGE_KERN* macros, do not mask off any bits by default: */
+pteval_t __default_kernel_pte_mask __read_mostly = ~0;
 
 /* Simplified build-specific string for starting entropy. */
 static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
_

[PATCH] x86, boot: initialize __default_kernel_pte_mask in KASLR code

[Dave Hansen]

The somewhat discrete arch/x86/boot/compressed code shares headers with
the main kernel, but needs its own copies of some variables.  The copy
of __default_kernel_pte_mask did not get initialized correctly and has
been reported to cause boot failures when KASLR is in use by Tom
Lendacky and Mike Galibrath.

I've oddly been unable to reproduce these, but the fix is simple and
confirmed to work by Tom and Mike.

Signed-off-by: Dave Hansen 
Fixes: 64c80759408f ("x86/mm: Do not auto-massage page protections")
Cc: Tom Lendacky 
Cc: Mike Galbraith 
Cc: Andy Lutomirski 
Cc: Arjan van de Ven 
Cc: Borislav Petkov 
Cc: Dan Williams 
Cc: David Woodhouse 
Cc: Greg Kroah-Hartman 
Cc: Hugh Dickins 
Cc: Josh Poimboeuf 
Cc: Juergen Gross 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Nadav Amit 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux...@kvack.org
---

 b/arch/x86/boot/compressed/kaslr.c |4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN 
arch/x86/boot/compressed/kaslr.c~x86-boot-initialize-__default_kernel_pte_mask 
arch/x86/boot/compressed/kaslr.c
--- 
a/arch/x86/boot/compressed/kaslr.c~x86-boot-initialize-__default_kernel_pte_mask
2018-04-10 13:02:22.359914088 -0700
+++ b/arch/x86/boot/compressed/kaslr.c  2018-04-10 13:02:40.389914043 -0700
@@ -54,8 +54,8 @@ unsigned int ptrs_per_p4d __ro_after_ini
 
 extern unsigned long get_cmd_line_ptr(void);
 
-/* Used by PAGE_KERN* macros: */
-pteval_t __default_kernel_pte_mask __read_mostly;
+/* Used by PAGE_KERN* macros, do not mask off any bits by default: */
+pteval_t __default_kernel_pte_mask __read_mostly = ~0;
 
 /* Simplified build-specific string for starting entropy. */
 static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
_