linux-kernel - [tip:mm/readonly] lkdtm: Verify that '__ro_after

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tip-7cca071ccbd2a293ea69168ace6abbcdce53098e@git.kernel.org>
Date:	Mon, 22 Feb 2016 04:19:57 -0800
From:	tip-bot for Kees Cook <tipbot@...or.com>@zytor.com
To:	linux-tip-commits@...r.kernel.org@...or.com
Cc:	linux-kernel@...r.kernel.org, brgerst@...il.com, bp@...en8.de,
	peterz@...radead.org, mingo@...nel.org, dvlasenk@...hat.com,
	minipli@...glemail.com, linux-arch@...r.kernel.org,
	torvalds@...ux-foundation.org, mpe@...erman.id.au, hpa@...or.com,
	tglx@...utronix.de, arnd@...db.de, david.brown@...aro.org,
	luto@...capital.net, pageexec@...email.hu, keescook@...omium.org,
	re.emese@...il.com
Subject: [tip:mm/readonly] lkdtm: Verify that '__ro_after_init' works correctly

Commit-ID:  7cca071ccbd2a293ea69168ace6abbcdce53098e
Gitweb:     http://git.kernel.org/tip/7cca071ccbd2a293ea69168ace6abbcdce53098e
Author:     Kees Cook <keescook@...omium.org>
AuthorDate: Wed, 17 Feb 2016 14:41:16 -0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 22 Feb 2016 08:51:38 +0100

lkdtm: Verify that '__ro_after_init' works correctly

The new __ro_after_init section should be writable before init, but
not after. Validate that it gets updated at init and can't be written
to afterwards.

Signed-off-by: Kees Cook <keescook@...omium.org>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: David Brown <david.brown@...aro.org>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Emese Revfy <re.emese@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mathias Krause <minipli@...glemail.com>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: PaX Team <pageexec@...email.hu>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: kernel-hardening@...ts.openwall.com
Cc: linux-arch <linux-arch@...r.kernel.org>
Link: http://lkml.kernel.org/r/1455748879-21872-6-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 drivers/misc/lkdtm.c | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index 11fdadc..2a6eaf1 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -103,6 +103,7 @@ enum ctype {
 	CT_EXEC_USERSPACE,
 	CT_ACCESS_USERSPACE,
 	CT_WRITE_RO,
+	CT_WRITE_RO_AFTER_INIT,
 	CT_WRITE_KERN,
 };
 
@@ -140,6 +141,7 @@ static char* cp_type[] = {
 	"EXEC_USERSPACE",
 	"ACCESS_USERSPACE",
 	"WRITE_RO",
+	"WRITE_RO_AFTER_INIT",
 	"WRITE_KERN",
 };
 
@@ -162,6 +164,7 @@ static DEFINE_SPINLOCK(lock_me_up);
 static u8 data_area[EXEC_SIZE];
 
 static const unsigned long rodata = 0xAA55AA55;
+static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
 
 module_param(recur_count, int, 0644);
 MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test");
@@ -503,11 +506,28 @@ static void lkdtm_do_action(enum ctype which)
 		break;
 	}
 	case CT_WRITE_RO: {
-		unsigned long *ptr;
+		/* Explicitly cast away "const" for the test. */
+		unsigned long *ptr = (unsigned long *)&rodata;
 
-		ptr = (unsigned long *)&rodata;
+		pr_info("attempting bad rodata write at %p\n", ptr);
+		*ptr ^= 0xabcd1234;
 
-		pr_info("attempting bad write at %p\n", ptr);
+		break;
+	}
+	case CT_WRITE_RO_AFTER_INIT: {
+		unsigned long *ptr = &ro_after_init;
+
+		/*
+		 * Verify we were written to during init. Since an Oops
+		 * is considered a "success", a failure is to just skip the
+		 * real test.
+		 */
+		if ((*ptr & 0xAA) != 0xAA) {
+			pr_info("%p was NOT written during init!?\n", ptr);
+			break;
+		}
+
+		pr_info("attempting bad ro_after_init write at %p\n", ptr);
 		*ptr ^= 0xabcd1234;
 
 		break;
@@ -817,6 +837,9 @@ static int __init lkdtm_module_init(void)
 	int n_debugfs_entries = 1; /* Assume only the direct entry */
 	int i;
 
+	/* Make sure we can write to __ro_after_init values during __init */
+	ro_after_init |= 0xAA;
+
 	/* Register debugfs interface */
 	lkdtm_debugfs_root = debugfs_create_dir("provoke-crash", NULL);
 	if (!lkdtm_debugfs_root) {