Unfortunately, list_empty() is not usable with an entry that has been removed from a list with list_del_rcu() as ->next must be left pointing at the following entry so as not to break traversal under RCU.
Solve this by moving on_list_rcu() from AppArmor to linux/list.h, and turning it into an inline function. Also add an on_list() counterpart (functionally, this is just an antonym for list_empty()), but the name looks less awkward when applied to a non-head element. We probably don't want to use on_list_rcu() generally because it requires an extra check as ->prev is set differently in the two cases. Signed-off-by: David Howells <[email protected]> cc: Mathieu Desnoyers <[email protected]> cc: John Johansen <[email protected]> cc: Marc Dionne <[email protected]> cc: Eric Dumazet <[email protected]> cc: "David S. Miller" <[email protected]> cc: Jakub Kicinski <[email protected]> cc: Paolo Abeni <[email protected]> cc: Simon Horman <[email protected]> cc: [email protected] cc: [email protected] cc: [email protected] cc: [email protected] --- include/linux/list.h | 26 ++++++++++++++++++++++++++ security/apparmor/include/policy.h | 2 -- 2 files changed, 26 insertions(+), 2 deletions(-) diff --git a/include/linux/list.h b/include/linux/list.h index 00ea8e5fb88b..d224e7210d1b 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -381,6 +381,32 @@ static inline int list_empty(const struct list_head *head) return READ_ONCE(head->next) == head; } +/** + * on_list - Test whether an entry is on a list. + * @entry: The entry to check + * + * Test whether an entry is on a list. Safe to use on an entry initialised + * with INIT_LIST_HEAD() or LIST_HEAD() or removed with things like + * list_del_init(). Not safe for use with list_del() or list_del_rcu(). + */ +static inline bool on_list(const struct list_head *entry) +{ + return !list_empty(entry); +} + +/** + * on_list_rcu - Test whether an entry is on a list (RCU-del safe). + * @entry: The entry to check + * + * Test whether an entry is on a list. Safe to use on an entry initialised + * with INIT_LIST_HEAD() or LIST_HEAD() or removed with things like + * list_del_init(). Also safe for use with list_del() or list_del_rcu(). + */ +static inline bool on_list_rcu(const struct list_head *entry) +{ + return !list_empty(entry) && entry->prev != LIST_POISON2; +} + /** * list_del_init_careful - deletes entry from list and reinitialize it. * @entry: the element to delete from the list. diff --git a/security/apparmor/include/policy.h b/security/apparmor/include/policy.h index 3895f8774a3f..c3697c23bbed 100644 --- a/security/apparmor/include/policy.h +++ b/security/apparmor/include/policy.h @@ -57,8 +57,6 @@ extern const char *const aa_profile_mode_names[]; #define profile_is_stale(_profile) (label_is_stale(&(_profile)->label)) -#define on_list_rcu(X) (!list_empty(X) && (X)->prev != LIST_POISON2) - /* flags in the dfa accept2 table */ enum dfa_accept_flags { ACCEPT_FLAG_OWNER = 1,
