Commit-ID: d7c816733d501b59dbdc2483f2cc8e4431fd9160
Gitweb: http://git.kernel.org/tip/d7c816733d501b59dbdc2483f2cc8e4431fd9160
Author: Kees Cook <keescook@xxxxxxxxxxxx>
AuthorDate: Wed, 17 Aug 2016 14:42:08 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Mon, 31 Oct 2016 13:01:56 -0700
list: Split list_add() debug checking into separate function
Right now, __list_add() code is repeated either in list.h or in
list_debug.c, but the only differences between the two versions
are the debug checks. This commit therefore extracts these debug
checks into a separate __list_add_valid() function and consolidates
__list_add(). Additionally this new __list_add_valid() function will stop
list manipulations if a corruption is detected, instead of allowing for
further corruption that may lead to even worse conditions.
This is slight refactoring of the same hardening done in PaX and Grsecurity.
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
---
include/linux/list.h | 22 ++++++++++++++++------
lib/list_debug.c | 48 +++++++++++++++++++++++-------------------------
2 files changed, 39 insertions(+), 31 deletions(-)
diff --git a/include/linux/list.h b/include/linux/list.h
index 5809e9a..b6da9b1 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -28,27 +28,37 @@ static inline void INIT_LIST_HEAD(struct list_head *list)
list->prev = list;
}
+#ifdef CONFIG_DEBUG_LIST
+extern bool __list_add_valid(struct list_head *new,
+ struct list_head *prev,
+ struct list_head *next);
+#else
+static inline bool __list_add_valid(struct list_head *new,
+ struct list_head *prev,
+ struct list_head *next)
+{
+ return true;
+}
+#endif
+
/*
* Insert a new entry between two known consecutive entries.
*
* This is only for internal list manipulation where we know
* the prev/next entries already!
*/
-#ifndef CONFIG_DEBUG_LIST
static inline void __list_add(struct list_head *new,
struct list_head *prev,
struct list_head *next)
{
+ if (!__list_add_valid(new, prev, next))
+ return;
+
next->prev = new;
new->next = next;
new->prev = prev;
WRITE_ONCE(prev->next, new);
}
-#else
-extern void __list_add(struct list_head *new,
- struct list_head *prev,
- struct list_head *next);
-#endif
/**
* list_add - add a new entry
diff --git a/lib/list_debug.c b/lib/list_debug.c
index 3859bf6..149dd57 100644
--- a/lib/list_debug.c
+++ b/lib/list_debug.c
@@ -2,8 +2,7 @@
* Copyright 2006, Red Hat, Inc., Dave Jones
* Released under the General Public License (GPL).
*
- * This file contains the linked list implementations for
- * DEBUG_LIST.
+ * This file contains the linked list validation for DEBUG_LIST.
*/
#include <linux/export.h>
@@ -13,33 +12,32 @@
#include <linux/rculist.h>
/*
- * Insert a new entry between two known consecutive entries.
- *
- * This is only for internal list manipulation where we know
- * the prev/next entries already!
+ * Check that the data structures for the list manipulations are reasonably
+ * valid. Failures here indicate memory corruption (and possibly an exploit
+ * attempt).
*/
-void __list_add(struct list_head *new,
- struct list_head *prev,
- struct list_head *next)
+bool __list_add_valid(struct list_head *new, struct list_head *prev,
+ struct list_head *next)
{
- WARN(next->prev != prev,
- "list_add corruption. next->prev should be "
- "prev (%p), but was %p. (next=%p).\n",
- prev, next->prev, next);
- WARN(prev->next != next,
- "list_add corruption. prev->next should be "
- "next (%p), but was %p. (prev=%p).\n",
- next, prev->next, prev);
- WARN(new == prev || new == next,
- "list_add double add: new=%p, prev=%p, next=%p.\n",
- new, prev, next);
- next->prev = new;
- new->next = next;
- new->prev = prev;
- WRITE_ONCE(prev->next, new);
+ if (unlikely(next->prev != prev)) {
+ WARN(1, "list_add corruption. next->prev should be prev (%p), but was %p. (next=%p).\n",
+ prev, next->prev, next);
+ return false;
+ }
+ if (unlikely(prev->next != next)) {
+ WARN(1, "list_add corruption. prev->next should be next (%p), but was %p. (prev=%p).\n",
+ next, prev->next, prev);
+ return false;
+ }
+ if (unlikely(new == prev || new == next)) {
+ WARN(1, "list_add double add: new=%p, prev=%p, next=%p.\n",
+ new, prev, next);
+ return false;
+ }
+ return true;
}
-EXPORT_SYMBOL(__list_add);
+EXPORT_SYMBOL(__list_add_valid);
void __list_del_entry(struct list_head *entry)
{
--
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