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list: Split list_add() debug checking into separate function

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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@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>
This commit is contained in:
Kees Cook
2016-08-17 14:42:08 -07:00
committed by Paul E. McKenney
parent 1001354ca3
commit d7c816733d
2 changed files with 39 additions and 31 deletions
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22
include/linux/list.h
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@@ -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