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 <[email protected]> Fixes: 64c80759408f ("x86/mm: Do not auto-massage page protections") Cc: Tom Lendacky <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Arjan van de Ven <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dan Williams <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Greg Kroah-Hartman <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Juergen Gross <[email protected]> Cc: Kees Cook <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Nadav Amit <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] --- 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 "@" _
