Paul E. McKenney wrote:
> On Sat, Nov 12, 2016 at 11:26:15PM +0900, Tetsuo Handa wrote:
> > Both head->r.acl and
> > &tomoyo_kernel_namespace.policy_list[TOMOYO_ID_MANAGER]->next
> > refer normal kernel address space. Thus, I think that this warning is a
> > false positive.
> >
> > This warning goes away if I disable rcu_dereference_sparse() call in
> > __rcu_dereference_check() from srcu_dereference_check() from
> > srcu_dereference().
> >
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -605,7 +605,7 @@ static inline void rcu_preempt_sleep_check(void)
> > /* Dependency order vs. p above. */ \
> > typeof(*p) *________p1 = (typeof(*p)
> > *__force)lockless_dereference(p); \
> > RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage");
> > \
> > - rcu_dereference_sparse(p, space); \
> > + /*rcu_dereference_sparse(p, space); */ \
> > ((typeof(*p) __force __kernel *)(________p1)); \
> > })
> > #define __rcu_dereference_protected(p, c, space) \
>
> OK.
>
> One approach would be for you to replace your:
>
> pos = srcu_dereference((head)->next, &tomoyo_ss);
>
> with:
>
> pos = ecu_dereference_raw((head)->next);
>
> This will suppress the sparse complaint, but would also suppress the
> lockdep complaint about using list_for_each_cookie() unprotected by an
> SRCU read-side critical section. But this can be handled by placing an
> appropriate RCU_LOCKDEP_WARN() in list_for_each_cookie().
>
> Does that work for you?
Yes, I can use below approach. Thank you.
--- a/security/tomoyo/common.h
+++ b/security/tomoyo/common.h
@@ -1317,14 +1317,20 @@ static inline int tomoyo_round2(size_t size)
#endif
+static inline void tomoyo_read_lock_check(void)
+{
+ RCU_LOCKDEP_WARN(!srcu_read_lock_held(&tomoyo_ss),
+ "tomoyo_ss lock is not held.");
+}
+
/**
* list_for_each_cookie - iterate over a list with cookie.
* @pos: the &struct list_head to use as a loop cursor.
* @head: the head for your list.
*/
#define list_for_each_cookie(pos, head)
\
- if (!pos) \
- pos = srcu_dereference((head)->next, &tomoyo_ss); \
- for ( ; pos != (head); pos = srcu_dereference(pos->next, &tomoyo_ss))
+ for (pos = pos ? pos : rcu_dereference_raw((head)->next); \
+ tomoyo_read_lock_check(), pos != (head); \
+ pos = rcu_dereference_raw(pos->next))
#endif /* !defined(_SECURITY_TOMOYO_COMMON_H) */
