4.14-stable review patch. If anyone has any objections, please let me know.
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From: Dave Hansen dave.hansen@linux.intel.com
commit 1c4de1ff4fe50453b968579ee86fac3da80dd783 upstream.
With PAGE_TABLE_ISOLATION the user portion of the kernel page tables is poisoned with the NX bit so if the entry code exits with the kernel page tables selected in CR3, userspace crashes.
But doing so trips the p4d/pgd_bad() checks. Make sure it does not do that.
Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Borislav Petkov bp@suse.de Cc: Andy Lutomirski luto@kernel.org Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Borislav Petkov bp@alien8.de Cc: Brian Gerst brgerst@gmail.com Cc: David Laight David.Laight@aculab.com Cc: Denys Vlasenko dvlasenk@redhat.com Cc: Eduardo Valentin eduval@amazon.com Cc: Greg KH gregkh@linuxfoundation.org Cc: H. Peter Anvin hpa@zytor.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Juergen Gross jgross@suse.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Will Deacon will.deacon@arm.com Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/include/asm/pgtable.h | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)
--- 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 *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_PAGE_TABLE_ISOLATION)) + 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 *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_PAGE_TABLE_ISOLATION)) + ignore_flags |= _PAGE_NX; + + return (pgd_flags(pgd) & ~ignore_flags) != _KERNPG_TABLE; }
static inline int pgd_none(pgd_t pgd)