[PATCH 26/43] x86/mm/kaiser: Allow NX poison to be set in p4d/pgd

[Ingo Molnar]

From: Dave Hansen <dave.han...@linux.intel.com>

The user portion of the kernel page tables use the NX bit to
poison them for userspace.  But, that trips the p4d/pgd_bad()
checks.  Make sure it does not do that.

Signed-off-by: Dave Hansen <dave.han...@linux.intel.com>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Brian Gerst <brge...@gmail.com>
Cc: Daniel Gruss <daniel.gr...@iaik.tugraz.at>
Cc: Denys Vlasenko <dvlas...@redhat.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Hugh Dickins <hu...@google.com>
Cc: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Kees Cook <keesc...@google.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Michael Schwarz <michael.schw...@iaik.tugraz.at>
Cc: Moritz Lipp <moritz.l...@iaik.tugraz.at>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Richard Fellner <richard.fell...@student.tugraz.at>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: linux...@kvack.org
Link: http://lkml.kernel.org/r/20171123003448.c6ab3...@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
 arch/x86/include/asm/pgtable.h | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index d3901124143f..9cceaf6c0405 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -846,7 +846,12 @@ static inline pud_t *pud_offset(p4d_t *p4d, unsigned long 
address)
 
 static inline int p4d_bad(p4d_t p4d)
 {
-       return (p4d_flags(p4d) & ~(_KERNPG_TABLE | _PAGE_USER)) != 0;
+       unsigned long ignore_flags = _KERNPG_TABLE | _PAGE_USER;
+
+       if (IS_ENABLED(CONFIG_KAISER))
+               ignore_flags |= _PAGE_NX;
+
+       return (p4d_flags(p4d) & ~ignore_flags) != 0;
 }
 #endif  /* CONFIG_PGTABLE_LEVELS > 3 */
 
@@ -880,7 +885,12 @@ static inline p4d_t *p4d_offset(pgd_t *pgd, unsigned long 
address)
 
 static inline int pgd_bad(pgd_t pgd)
 {
-       return (pgd_flags(pgd) & ~_PAGE_USER) != _KERNPG_TABLE;
+       unsigned long ignore_flags = _PAGE_USER;
+
+       if (IS_ENABLED(CONFIG_KAISER))
+               ignore_flags |= _PAGE_NX;
+
+       return (pgd_flags(pgd) & ~ignore_flags) != _KERNPG_TABLE;
 }
 
 static inline int pgd_none(pgd_t pgd)
-- 
2.14.1