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Message-Id: <1471381865-25724-2-git-send-email-keescook@chromium.org>
Date: Tue, 16 Aug 2016 14:11:01 -0700
From: Kees Cook <keescook@...omium.org>
To: "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: Kees Cook <keescook@...omium.org>,
Stephen Boyd <sboyd@...eaurora.org>,
Daniel Micay <danielmicay@...il.com>,
Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Josh Triplett <josh@...htriplett.org>,
Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Tejun Heo <tj@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dan Williams <dan.j.williams@...el.com>,
Jan Kara <jack@...e.cz>,
Josef Bacik <jbacik@...com>,
Thomas Gleixner <tglx@...utronix.de>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH 1/5] 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 only the debug checks are the different part. This
extracts the checking into a separate function and consolidates
__list_add(). Additionally this __list_add_debug() 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@...omium.org>
---
include/linux/list.h | 22 ++++++++++++++++------
lib/list_debug.c | 35 ++++++++++++++++++-----------------
2 files changed, 34 insertions(+), 23 deletions(-)
diff --git a/include/linux/list.h b/include/linux/list.h
index 5183138aa932..c38ff652ab59 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_debug(struct list_head *new,
+ struct list_head *prev,
+ struct list_head *next);
+#else
+static inline bool __list_add_debug(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_debug(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 3859bf63561c..5d78982eeb99 100644
--- a/lib/list_debug.c
+++ b/lib/list_debug.c
@@ -19,27 +19,28 @@
* the prev/next entries already!
*/
-void __list_add(struct list_head *new,
+bool __list_add_debug(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_debug);
void __list_del_entry(struct list_head *entry)
{
--
2.7.4
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