lkdtm: Add tests for struct list corruption

When building under CONFIG_DEBUG_LIST, list addition and removal will be
sanity-checked. This validates that the check is working as expected by
setting up classic corruption attacks against list manipulations, available
with the new lkdtm tests CORRUPT_LIST_ADD and CORRUPT_LIST_DEL.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Rik van Riel <riel@redhat.com>

3 files changed, 72 insertions, 0 deletions

diff --git a/drivers/misc/lkdtm.h b/drivers/misc/lkdtm.h
index fdf954c2107f..cfa1039c62e7 100644
--- a/drivers/misc/lkdtm.h
+++ b/drivers/misc/lkdtm.h
@@ -21,6 +21,8 @@ void lkdtm_SPINLOCKUP(void);
 void lkdtm_HUNG_TASK(void);
 void lkdtm_ATOMIC_UNDERFLOW(void);
 void lkdtm_ATOMIC_OVERFLOW(void);
+void lkdtm_CORRUPT_LIST_ADD(void);
+void lkdtm_CORRUPT_LIST_DEL(void);
 
 /* lkdtm_heap.c */
 void lkdtm_OVERWRITE_ALLOCATION(void);
diff --git a/drivers/misc/lkdtm_bugs.c b/drivers/misc/lkdtm_bugs.c
index 182ae1894b32..f336206d4b1f 100644
--- a/drivers/misc/lkdtm_bugs.c
+++ b/drivers/misc/lkdtm_bugs.c
@@ -5,8 +5,13 @@
  * test source files.
  */
 #include "lkdtm.h"
+#include <linux/list.h>
 #include <linux/sched.h>
 
+struct lkdtm_list {
+        struct list_head node;
+};
+
 /*
  * Make sure our attempts to over run the kernel stack doesn't trigger
  * a compiler warning when CONFIG_FRAME_WARN is set. Then make sure we
@@ -146,3 +151,66 @@ void lkdtm_ATOMIC_OVERFLOW(void)
         pr_info("attempting bad atomic overflow\n");
         atomic_inc(&over);
 }
+
+void lkdtm_CORRUPT_LIST_ADD(void)
+{
+        /*
+         * Initially, an empty list via LIST_HEAD:
+         *      test_head.next = &test_head
+         *      test_head.prev = &test_head
+         */
+        LIST_HEAD(test_head);
+        struct lkdtm_list good, bad;
+        void *target[2] = { };
+        void *redirection = &target;
+
+        pr_info("attempting good list addition\n");
+
+        /*
+         * Adding to the list performs these actions:
+         *      test_head.next->prev = &good.node
+         *      good.node.next = test_head.next
+         *      good.node.prev = test_head
+         *      test_head.next = good.node
+         */
+        list_add(&good.node, &test_head);
+
+        pr_info("attempting corrupted list addition\n");
+        /*
+         * In simulating this "write what where" primitive, the "what" is
+         * the address of &bad.node, and the "where" is the address held
+         * by "redirection".
+         */
+        test_head.next = redirection;
+        list_add(&bad.node, &test_head);
+
+        if (target[0] == NULL && target[1] == NULL)
+                pr_err("Overwrite did not happen, but no BUG?!\n");
+        else
+                pr_err("list_add() corruption not detected!\n");
+}
+
+void lkdtm_CORRUPT_LIST_DEL(void)
+{
+        LIST_HEAD(test_head);
+        struct lkdtm_list item;
+        void *target[2] = { };
+        void *redirection = &target;
+
+        list_add(&item.node, &test_head);
+
+        pr_info("attempting good list removal\n");
+        list_del(&item.node);
+
+        pr_info("attempting corrupted list removal\n");
+        list_add(&item.node, &test_head);
+
+        /* As with the list_add() test above, this corrupts "next". */
+        item.node.next = redirection;
+        list_del(&item.node);
+
+        if (target[0] == NULL && target[1] == NULL)
+                pr_err("Overwrite did not happen, but no BUG?!\n");
+        else
+                pr_err("list_del() corruption not detected!\n");
+}
diff --git a/drivers/misc/lkdtm_core.c b/drivers/misc/lkdtm_core.c
index f9154b8d67f6..7eeb71a75549 100644
--- a/drivers/misc/lkdtm_core.c
+++ b/drivers/misc/lkdtm_core.c
@@ -197,6 +197,8 @@ struct crashtype crashtypes[] = {
         CRASHTYPE(EXCEPTION),
         CRASHTYPE(LOOP),
         CRASHTYPE(OVERFLOW),
+        CRASHTYPE(CORRUPT_LIST_ADD),
+        CRASHTYPE(CORRUPT_LIST_DEL),
         CRASHTYPE(CORRUPT_STACK),
         CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
         CRASHTYPE(OVERWRITE_ALLOCATION),