x86/mm/pti: Clone entry-text again in pti_finalize()

CVE-2017-5754

The mapping for entry-text might have changed in the kernel after it was
cloned to the user page-table. Clone again to update the user page-table to
bring the mapping in sync with the kernel again.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Pavel Machek <pavel@ucw.cz>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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: 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: Andrea Arcangeli <aarcange@redhat.com>
Cc: Waiman Long <llong@redhat.com>
Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca>
Cc: joro@8bytes.org
Link: https://lkml.kernel.org/r/1531906876-13451-31-git-send-email-joro@8bytes.org
(cherry picked from commit ba0364e260ab37c02975557dbecc014a26072236)
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index dfc545ced03333eba3b654615ddbc609463426ab..6aab99307c3425b62f0b9cc6985eeadb7bf8fbe9 100644 (file)
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -405,7 +405,7 @@ static void __init pti_setup_espfix64(void)
 /*
  * Clone the populated PMDs of the entry and irqentry text and force it RO.
  */
-static void __init pti_clone_entry_text(void)
+static void pti_clone_entry_text(void)
 {
        pti_clone_pmds((unsigned long) __entry_text_start,
                        (unsigned long) __irqentry_text_end,
@@ -529,13 +529,18 @@ void __init pti_init(void)
 }
 
 /*
- * Finalize the kernel mappings in the userspace page-table.
+ * Finalize the kernel mappings in the userspace page-table. Some of the
+ * mappings for the kernel image might have changed since pti_init()
+ * cloned them. This is because parts of the kernel image have been
+ * mapped RO and/or NX.  These changes need to be cloned again to the
+ * userspace page-table.
  */
 void pti_finalize(void)
 {
        /*
-        * Do this after all of the manipulation of the
-        * kernel text page tables are complete.
+        * We need to clone everything (again) that maps parts of the
+        * kernel image.
         */
+       pti_clone_entry_text();
        pti_clone_kernel_text();
 }