Messages in this thread Patch in this message | | | Subject | [PATCH 10/30] x86, kaiser: allow NX to be set in p4d/pgd | From | Dave Hansen <> | Date | Wed, 08 Nov 2017 11:47:04 -0800 |
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From: Dave Hansen <dave.hansen@linux.intel.com>
We protect user portion of the kernel page tables with the NX bit to cripple it. But, that trips the p4d/pgd_bad() checks. Make sure it does not do that.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Moritz Lipp <moritz.lipp@iaik.tugraz.at> Cc: Daniel Gruss <daniel.gruss@iaik.tugraz.at> Cc: Michael Schwarz <michael.schwarz@iaik.tugraz.at> Cc: Richard Fellner <richard.fellner@student.tugraz.at> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Kees Cook <keescook@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: x86@kernel.org ---
b/arch/x86/include/asm/pgtable.h | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)
diff -puN arch/x86/include/asm/pgtable.h~kaiser-p4d-allow-nx arch/x86/include/asm/pgtable.h --- a/arch/x86/include/asm/pgtable.h~kaiser-p4d-allow-nx 2017-11-08 10:45:31.308681390 -0800 +++ b/arch/x86/include/asm/pgtable.h 2017-11-08 10:45:31.312681390 -0800 @@ -845,7 +845,12 @@ static inline pud_t *pud_offset(p4d_t *p 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 */ @@ -879,7 +884,12 @@ static inline p4d_t *p4d_offset(pgd_t *p 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) _
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