From: Kees Cook <keescook@chromium.org>
To: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>,
Andy Lutomirski <luto@amacapital.net>,
"H. Peter Anvin" <hpa@zytor.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Mathias Krause <minipli@googlemail.com>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
x86@kernel.org, Arnd Bergmann <arnd@arndb.de>,
PaX Team <pageexec@freemail.hu>, Emese Revfy <re.emese@gmail.com>,
kernel-hardening@lists.openwall.com,
linux-arch <linux-arch@vger.kernel.org>
Subject: [kernel-hardening] [PATCH v2 3/4] lkdtm: verify that __ro_after_init works correctly
Date: Wed, 25 Nov 2015 15:31:25 -0800 [thread overview]
Message-ID: <1448494286-16029-4-git-send-email-keescook@chromium.org> (raw)
In-Reply-To: <1448494286-16029-1-git-send-email-keescook@chromium.org>
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@chromium.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 11fdadc68e53..2a6eaf1122b4 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) {
--
1.9.1
next prev parent reply other threads:[~2015-11-25 23:31 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-25 23:31 [kernel-hardening] [PATCH v2 0/4] introduce post-init read-only memory Kees Cook
2015-11-25 23:31 ` [kernel-hardening] [PATCH v2 1/4] init: create cmdline param to disable readonly Kees Cook
2015-11-26 0:37 ` [kernel-hardening] " PaX Team
2015-11-26 0:44 ` [kernel-hardening] " Greg KH
2015-11-26 7:51 ` [kernel-hardening] " Ingo Molnar
2015-11-30 21:52 ` Kees Cook
2015-11-30 22:24 ` Russell King - ARM Linux
2015-11-30 22:34 ` Kees Cook
2015-12-01 7:24 ` Ingo Molnar
2015-12-01 7:19 ` Heiko Carstens
2015-11-25 23:31 ` [kernel-hardening] [PATCH v2 2/4] introduce post-init read-only memory Kees Cook
2015-11-26 0:15 ` [kernel-hardening] " PaX Team
2015-11-30 22:24 ` H. Peter Anvin
2015-12-09 19:35 ` Kees Cook
2015-11-25 23:31 ` Kees Cook [this message]
2015-11-25 23:31 ` [kernel-hardening] [PATCH v2 4/4] x86, vdso: mark vDSO read-only after init Kees Cook
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