lkdtm: add bad USER_DS test
This adds CORRUPT_USER_DS to check that the get_fs() test on syscall
return (via __VERIFY_PRE_USERMODE_STATE) still sees USER_DS. Since
trying to deal with values other than USER_DS and KERNEL_DS across all
architectures in a safe way is not sensible, this sets KERNEL_DS, but
since that could be extremely dangerous if the protection is not present,
it also raises SIGKILL for current, so that no matter what, the process
will die. A successful test will be visible with a BUG(), like all the
other LKDTM tests.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/misc/lkdtm_bugs.c b/drivers/misc/lkdtm_bugs.c
index e3f4cd8..ed4f4c5 100644
--- a/drivers/misc/lkdtm_bugs.c
+++ b/drivers/misc/lkdtm_bugs.c
@@ -8,6 +8,8 @@
#include <linux/list.h>
#include <linux/refcount.h>
#include <linux/sched.h>
+#include <linux/sched/signal.h>
+#include <linux/uaccess.h>
struct lkdtm_list {
struct list_head node;
@@ -279,3 +281,12 @@
else
pr_err("list_del() corruption not detected!\n");
}
+
+void lkdtm_CORRUPT_USER_DS(void)
+{
+ pr_info("setting bad task size limit\n");
+ set_fs(KERNEL_DS);
+
+ /* Make sure we do not keep running with a KERNEL_DS! */
+ force_sig(SIGKILL, current);
+}