lkdtm: add "WRITE_KERN" test
Add "WRITE_KERN" crash target to validate that kernel executable memory
is not writable.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index d6ee1aa..d303011 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -102,6 +102,7 @@
CT_EXEC_USERSPACE,
CT_ACCESS_USERSPACE,
CT_WRITE_RO,
+ CT_WRITE_KERN,
};
static char* cp_name[] = {
@@ -138,6 +139,7 @@
"EXEC_USERSPACE",
"ACCESS_USERSPACE",
"WRITE_RO",
+ "WRITE_KERN",
};
static struct jprobe lkdtm;
@@ -317,6 +319,13 @@
return;
}
+/* Must immediately follow do_nothing for size calculuations to work out. */
+static void do_overwritten(void)
+{
+ pr_info("do_overwritten wasn't overwritten!\n");
+ return;
+}
+
static noinline void corrupt_stack(void)
{
/* Use default char array length that triggers stack protection. */
@@ -496,6 +505,22 @@
break;
}
+ case CT_WRITE_KERN: {
+ size_t size;
+ unsigned char *ptr;
+
+ size = (unsigned long)do_overwritten -
+ (unsigned long)do_nothing;
+ ptr = (unsigned char *)do_overwritten;
+
+ pr_info("attempting bad %zu byte write at %p\n", size, ptr);
+ memcpy(ptr, (unsigned char *)do_nothing, size);
+ flush_icache_range((unsigned long)ptr,
+ (unsigned long)(ptr + size));
+
+ do_overwritten();
+ break;
+ }
case CT_NONE:
default:
break;