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

joergroedel · KAGA-KOKO · commit d878efce73fe · 2018-08-10T21:12:45.000+02:00
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. [ tglx: Folded !NX supported fix ] Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> 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: Pavel Machek <pavel@ucw.cz> Cc: "David H . Gutteridge" <dhgutteridge@sympatico.ca> Cc: joro@8bytes.org Link: https://lkml.kernel.org/r/1533727000-9172-1-git-send-email-joro@8bytes.org
diff --git 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);
 
 #ifdef CONFIG_DEBUG_WX
-#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()
 #else
-#define debug_checkwx() do { } while (0)
+#define debug_checkwx()		do { } while (0)
+#define debug_checkwx_user()	do { } while (0)
 #endif
 
 /*
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
@@ -569,12 +569,13 @@ void ptdump_walk_pgd_level_debugfs(struct seq_file *m, pgd_t *pgd, bool user)
 }
 EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs);
 
-static void ptdump_walk_user_pgd_level_checkwx(void)
+void ptdump_walk_user_pgd_level_checkwx(void)
 {
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 	pgd_t *pgd = INIT_PGD;
 
-	if (!static_cpu_has(X86_FEATURE_PTI))
+	if (!(__supported_pte_mask & _PAGE_NX) ||
+	    !static_cpu_has(X86_FEATURE_PTI))
 		return;
 
 	pr_info("x86/mm: Checking user space page tables\n");
@@ -586,7 +587,6 @@ 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
@@ -646,4 +646,6 @@ void pti_finalize(void)
 	 */
 	pti_clone_entry_text();
 	pti_clone_kernel_text();
+
+	debug_checkwx_user();
 }

Original file line number	Diff line number	Diff line change
`@@ -569,12 +569,13 @@ void ptdump_walk_pgd_level_debugfs(struct seq_file m, pgd_t pgd, bool user)`
`569`	`569`	`}`
`570`	`570`	`EXPORT_SYMBOL_GPL(ptdump_walk_pgd_level_debugfs);`
`571`	`571`
`572`		`-static void ptdump_walk_user_pgd_level_checkwx(void)`
	`572`	`+void ptdump_walk_user_pgd_level_checkwx(void)`
`573`	`573`	`{`
`574`	`574`	`#ifdef CONFIG_PAGE_TABLE_ISOLATION`
`575`	`575`	`pgd_t *pgd = INIT_PGD;`
`576`	`576`
`577`		`- if (!static_cpu_has(X86_FEATURE_PTI))`
	`577`	`+ if (!(__supported_pte_mask & _PAGE_NX) \|\|`
	`578`	`+ !static_cpu_has(X86_FEATURE_PTI))`
`578`	`579`	`return;`
`579`	`580`
`580`	`581`	`pr_info("x86/mm: Checking user space page tables\n");`
`@@ -586,7 +587,6 @@ static void ptdump_walk_user_pgd_level_checkwx(void)`
`586`	`587`	`void ptdump_walk_pgd_level_checkwx(void)`
`587`	`588`	`{`
`588`	`589`	`ptdump_walk_pgd_level_core(NULL, NULL, true, false);`
`589`		`- ptdump_walk_user_pgd_level_checkwx();`
`590`	`590`	`}`
`591`	`591`
`592`	`592`	`static int __init pt_dump_init(void)`
Original file line number	Diff line number	Diff line change
`@@ -646,4 +646,6 @@ void pti_finalize(void)`
`646`	`646`	`*/`
`647`	`647`	`pti_clone_entry_text();`
`648`	`648`	`pti_clone_kernel_text();`
	`649`	`+`
	`650`	`+ debug_checkwx_user();`
`649`	`651`	`}`