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Date: Wed, 29 Mar 2017 11:16:01 -0700
From: Kees Cook <keescook@...omium.org>
To: kernel-hardening@...ts.openwall.com
Cc: Kees Cook <keescook@...omium.org>,
Mark Rutland <mark.rutland@....com>,
Andy Lutomirski <luto@...nel.org>,
Hoeun Ryu <hoeun.ryu@...il.com>,
PaX Team <pageexec@...email.hu>,
Emese Revfy <re.emese@...il.com>,
Russell King <linux@...linux.org.uk>,
x86@...nel.org,
linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Subject: [RFC v2][PATCH 09/11] list: add rare_write() list helpers
Some structures that are intended to be made write-rarely are designed to
be linked by lists. As a result, there need to be rare_write()-supported
linked list primitives.
As found in PaX, this adds list management helpers for doing updates to
rarely-changed lists.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
include/linux/list.h | 17 +++++++++++++++++
lib/Makefile | 2 +-
lib/list_debug.c | 37 +++++++++++++++++++++++++++++++++++++
3 files changed, 55 insertions(+), 1 deletion(-)
diff --git a/include/linux/list.h b/include/linux/list.h
index ae537fa46216..50fdd5b737aa 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -126,6 +126,23 @@ static inline void list_del(struct list_head *entry)
entry->prev = LIST_POISON2;
}
+extern void __rare_list_add(struct list_head *new,
+ struct list_head *prev,
+ struct list_head *next);
+
+static inline void
+rare_list_add(__wr_rare_type struct list_head *new, struct list_head *head)
+{
+ __rare_list_add((struct list_head *)new, head, head->next);
+}
+static inline void
+rare_list_add_tail(__wr_rare_type struct list_head *new, struct list_head *head)
+{
+ __rare_list_add((struct list_head *)new, head->prev, head);
+}
+
+extern void rare_list_del(__wr_rare_type struct list_head *entry);
+
/**
* list_replace - replace old entry by new one
* @old : the element to be replaced
diff --git a/lib/Makefile b/lib/Makefile
index 320ac46a8725..cd64fd8f7a21 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -83,7 +83,7 @@ obj-$(CONFIG_BTREE) += btree.o
obj-$(CONFIG_INTERVAL_TREE) += interval_tree.o
obj-$(CONFIG_ASSOCIATIVE_ARRAY) += assoc_array.o
obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
-obj-$(CONFIG_DEBUG_LIST) += list_debug.o
+obj-y += list_debug.o
obj-$(CONFIG_DEBUG_OBJECTS) += debugobjects.o
ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
diff --git a/lib/list_debug.c b/lib/list_debug.c
index a34db8d27667..1add73f9479a 100644
--- a/lib/list_debug.c
+++ b/lib/list_debug.c
@@ -10,7 +10,9 @@
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/rculist.h>
+#include <linux/mm.h>
+#ifdef CONFIG_DEBUG_LIST
/*
* Check that the data structures for the list manipulations are reasonably
* valid. Failures here indicate memory corruption (and possibly an exploit
@@ -60,3 +62,38 @@ bool __list_del_entry_valid(struct list_head *entry)
}
EXPORT_SYMBOL(__list_del_entry_valid);
+
+#endif /* CONFIG_DEBUG_LIST */
+
+void __rare_list_add(struct list_head *new, struct list_head *prev,
+ struct list_head *next)
+{
+ if (!__list_add_valid(new, prev, next))
+ return;
+
+ rare_write_begin();
+ __rare_write(next->prev, new);
+ __rare_write(new->next, next);
+ __rare_write(new->prev, prev);
+ __rare_write(prev->next, new);
+ rare_write_end();
+}
+EXPORT_SYMBOL(__rare_list_add);
+
+void rare_list_del(__wr_rare_type struct list_head *entry_const)
+{
+ struct list_head *entry = (struct list_head *)entry_const;
+ struct list_head *prev = entry->prev;
+ struct list_head *next = entry->next;
+
+ if (!__list_del_entry_valid(entry))
+ return;
+
+ rare_write_begin();
+ __rare_write(next->prev, prev);
+ __rare_write(prev->next, next);
+ __rare_write(entry->next, LIST_POISON1);
+ __rare_write(entry->prev, LIST_POISON2);
+ rare_write_end();
+}
+EXPORT_SYMBOL(rare_list_del);
--
2.7.4
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