[tip:x86/pti] x86/mm/pti: Move user W+X check into pti_finalize()

From: tip-bot for Joerg Roedel
Date: Thu Aug 09 2018 - 14:48:37 EST

Commit-ID: a13c600e15de44ccf03df28d3311ef3cb754ed9b
Gitweb: https://git.kernel.org/tip/a13c600e15de44ccf03df28d3311ef3cb754ed9b
Author: Joerg Roedel <jroedel@xxxxxxx>
AuthorDate: Wed, 8 Aug 2018 13:16:40 +0200
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Thu, 9 Aug 2018 20:42:07 +0200

x86/mm/pti: Move user W+X check into pti_finalize()

The user page-table gets the updated kernel mappings in pti_finalize(),
which runs after the RO+X permissions got applied to the kernel page-table
in mark_readonly().

But with CONFIG_DEBUG_WX enabled, the user page-table is already checked in
mark_readonly() for insecure mappings. This causes false-positive
warnings, because the user page-table did not get the updated mappings yet.

Move the W+X check for the user page-table into pti_finalize() after it
updated all required mappings.

Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "H . Peter Anvin" <hpa@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Jiri Kosina <jkosina@xxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: David Laight <David.Laight@xxxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Eduardo Valentin <eduval@xxxxxxxxxx>
Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: aliguori@xxxxxxxxxx
Cc: daniel.gruss@xxxxxxxxxxxxxx
Cc: hughd@xxxxxxxxxx
Cc: keescook@xxxxxxxxxx
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Waiman Long <llong@xxxxxxxxxx>
Cc: Pavel Machek <pavel@xxxxxx>
Cc: "David H . Gutteridge" <dhgutteridge@xxxxxxxxxxxx>
Cc: joro@xxxxxxxxxx
Link: https://lkml.kernel.org/r/1533727000-9172-1-git-send-email-joro@xxxxxxxxxx

arch/x86/include/asm/pgtable.h | 7 +++++--
arch/x86/mm/dump_pagetables.c | 3 +--
arch/x86/mm/pti.c | 2 ++
3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index e39088cb59ab..a1cb3339da8d 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -30,11 +30,14 @@ int __init __early_make_pgtable(unsigned long address, pmdval_t pmd);
void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd);
void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user);
void ptdump_walk_pgd_level_checkwx(void);
+void ptdump_walk_user_pgd_level_checkwx(void);

-#define debug_checkwx() ptdump_walk_pgd_level_checkwx()
+#define debug_checkwx() ptdump_walk_pgd_level_checkwx()
+#define debug_checkwx_user() ptdump_walk_user_pgd_level_checkwx()
-#define debug_checkwx() do { } while (0)
+#define debug_checkwx() do { } while (0)
+#define debug_checkwx_user() do { } while (0)

diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index ccd92c4da57c..b8ab9012ffd6 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -569,7 +569,7 @@ void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user)

-static void ptdump_walk_user_pgd_level_checkwx(void)
+void ptdump_walk_user_pgd_level_checkwx(void)
pgd_t *pgd = INIT_PGD;
@@ -586,7 +586,6 @@ static void ptdump_walk_user_pgd_level_checkwx(void)
void ptdump_walk_pgd_level_checkwx(void)
ptdump_walk_pgd_level_core(NULL, NULL, true, false);
- ptdump_walk_user_pgd_level_checkwx();

static int __init pt_dump_init(void)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 1dc5c683e7a5..d58b4aba9510 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -646,4 +646,6 @@ void pti_finalize(void)
+ debug_checkwx_user();