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authorKees Cook <keescook@chromium.org>2016-02-17 14:41:16 -0800
committerIngo Molnar <mingo@kernel.org>2016-02-22 08:51:38 +0100
commit7cca071ccbd2a293ea69168ace6abbcdce53098e (patch)
tree33821bcd6ae1a50e176d715f174e96bd573045e4 /drivers/misc/lkdtm.c
parentc74ba8b3480da6ddaea17df2263ec09b869ac496 (diff)
downloadlinux-7cca071ccbd2a293ea69168ace6abbcdce53098e.tar.gz
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@chromium.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: David Brown <david.brown@linaro.org> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Emese Revfy <re.emese@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mathias Krause <minipli@googlemail.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: PaX Team <pageexec@freemail.hu> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: kernel-hardening@lists.openwall.com Cc: linux-arch <linux-arch@vger.kernel.org> Link: http://lkml.kernel.org/r/1455748879-21872-6-git-send-email-keescook@chromium.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'drivers/misc/lkdtm.c')
-rw-r--r--drivers/misc/lkdtm.c29
1 files 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) {