From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 4 Dec 2017 15:08:05 +0100
Subject: [PATCH] x86/mm/dump_pagetables: Check user space page table for WX
 pages
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CVE-2017-5754

ptdump_walk_pgd_level_checkwx() checks the kernel page table for WX pages,
but does not check the PAGE_TABLE_ISOLATION user space page table.

Restructure the code so that dmesg output is selected by an explicit
argument and not implicit via checking the pgd argument for !NULL.

Add the check for the user space page table.

Signed-off-by: Thomas Gleixner <tglx@linutronix.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: Dave Hansen <dave.hansen@linux.intel.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-mm@kvack.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit b4bf4f924b1d7bade38fd51b2e401d20d0956e4d)
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
(cherry picked from commit 1adfe82e8fe5afa2fae59efe498c461d5a52cb6c)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
 arch/x86/include/asm/pgtable.h |  1 +
 arch/x86/mm/debug_pagetables.c |  2 +-
 arch/x86/mm/dump_pagetables.c  | 30 +++++++++++++++++++++++++-----
 3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 25604b8a251a..4f5eb81cf8be 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -17,6 +17,7 @@
 #include <asm/x86_init.h>
 
 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);
 void ptdump_walk_pgd_level_checkwx(void);
 
 #ifdef CONFIG_DEBUG_WX
diff --git a/arch/x86/mm/debug_pagetables.c b/arch/x86/mm/debug_pagetables.c
index d1449fb6dc7a..8e70c1599e51 100644
--- a/arch/x86/mm/debug_pagetables.c
+++ b/arch/x86/mm/debug_pagetables.c
@@ -5,7 +5,7 @@
 
 static int ptdump_show(struct seq_file *m, void *v)
 {
-	ptdump_walk_pgd_level(m, NULL);
+	ptdump_walk_pgd_level_debugfs(m, NULL);
 	return 0;
 }
 
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index eed93dd4cb4a..7b022ad37c4e 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -457,7 +457,7 @@ static inline bool is_hypervisor_range(int idx)
 }
 
 static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
-				       bool checkwx)
+				       bool checkwx, bool dmesg)
 {
 #ifdef CONFIG_X86_64
 	pgd_t *start = (pgd_t *) &init_top_pgt;
@@ -470,7 +470,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 
 	if (pgd) {
 		start = pgd;
-		st.to_dmesg = true;
+		st.to_dmesg = dmesg;
 	}
 
 	st.check_wx = checkwx;
@@ -508,13 +508,33 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd,
 
 void ptdump_walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 {
-	ptdump_walk_pgd_level_core(m, pgd, false);
+	ptdump_walk_pgd_level_core(m, pgd, false, true);
+}
+
+void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd)
+{
+	ptdump_walk_pgd_level_core(m, pgd, false, false);
+}
+EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs);
+
+static void ptdump_walk_user_pgd_level_checkwx(void)
+{
+#ifdef CONFIG_PAGE_TABLE_ISOLATION
+	pgd_t *pgd = (pgd_t *) &init_top_pgt;
+
+	if (!static_cpu_has(X86_FEATURE_PTI))
+		return;
+
+	pr_info("x86/mm: Checking user space page tables\n");
+	pgd = kernel_to_user_pgdp(pgd);
+	ptdump_walk_pgd_level_core(NULL, pgd, true, false);
+#endif
 }
-EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level);
 
 void ptdump_walk_pgd_level_checkwx(void)
 {
-	ptdump_walk_pgd_level_core(NULL, NULL, true);
+	ptdump_walk_pgd_level_core(NULL, NULL, true, false);
+	ptdump_walk_user_pgd_level_checkwx();
 }
 
 static int __init pt_dump_init(void)
-- 
2.14.2

