From: Mateusz Guzik mjguzik@gmail.com
Some of the frequent consumers of get_cred and put_cred operate on 2 references on the same creds back-to-back.
Switch them to doing the work in one go instead.
Signed-off-by: Mateusz Guzik mjguzik@gmail.com [PM: removed changelog from commit description] Signed-off-by: Paul Moore paul@paul-moore.com Signed-off-by: Felix Fu fuzhen5@huawei.com --- include/linux/cred.h | 59 +++++++++++++++++++++++++++++++++++++------- kernel/cred.c | 26 ++++++++++--------- 2 files changed, 65 insertions(+), 20 deletions(-)
diff --git a/include/linux/cred.h b/include/linux/cred.h index f923528d5cc4..56bc432fe49b 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -218,6 +218,20 @@ static inline bool cap_ambient_invariant_ok(const struct cred *cred) cred->cap_inheritable)); }
+/** + * get_new_cred_many - Get references on a new set of credentials + * @cred: The new credentials to reference + * @nr: Number of references to acquire + * + * Get references on the specified set of new credentials. The caller must + * release all acquired references. + */ +static inline struct cred *get_new_cred_many(struct cred *cred, int nr) +{ + atomic_add(nr, &cred->usage); + return cred; +} + /** * get_new_cred - Get a reference on a new set of credentials * @cred: The new credentials to reference @@ -227,16 +241,16 @@ static inline bool cap_ambient_invariant_ok(const struct cred *cred) */ static inline struct cred *get_new_cred(struct cred *cred) { - atomic_inc(&cred->usage); - return cred; + return get_new_cred_many(cred, 1); }
/** - * get_cred - Get a reference on a set of credentials + * get_cred_many - Get references on a set of credentials * @cred: The credentials to reference + * @nr: Number of references to acquire * - * Get a reference on the specified set of credentials. The caller must - * release the reference. If %NULL is passed, it is returned with no action. + * Get references on the specified set of credentials. The caller must release + * all acquired reference. If %NULL is passed, it is returned with no action. * * This is used to deal with a committed set of credentials. Although the * pointer is const, this will temporarily discard the const and increment the @@ -244,14 +258,28 @@ static inline struct cred *get_new_cred(struct cred *cred) * accidental alteration of a set of credentials that should be considered * immutable. */ -static inline const struct cred *get_cred(const struct cred *cred) +static inline const struct cred *get_cred_many(const struct cred *cred, int nr) { struct cred *nonconst_cred = (struct cred *) cred; if (!cred) return cred; validate_creds(cred); nonconst_cred->non_rcu = 0; - return get_new_cred(nonconst_cred); + return get_new_cred_many(nonconst_cred, nr); +} + +/* + * get_cred - Get a reference on a set of credentials + * @cred: The credentials to reference + * + * Get a reference on the specified set of credentials. The caller must + * release the reference. If %NULL is passed, it is returned with no action. + * + * This is used to deal with a committed set of credentials. + */ +static inline const struct cred *get_cred(const struct cred *cred) +{ + return get_cred_many(cred, 1); }
static inline const struct cred *get_cred_rcu(const struct cred *cred) @@ -269,6 +297,7 @@ static inline const struct cred *get_cred_rcu(const struct cred *cred) /** * put_cred - Release a reference to a set of credentials * @cred: The credentials to release + * @nr: Number of references to release * * Release a reference to a set of credentials, deleting them when the last ref * is released. If %NULL is passed, nothing is done. @@ -277,17 +306,29 @@ static inline const struct cred *get_cred_rcu(const struct cred *cred) * on task_struct are attached by const pointers to prevent accidental * alteration of otherwise immutable credential sets. */ -static inline void put_cred(const struct cred *_cred) +static inline void put_cred_many(const struct cred *_cred, int nr) { struct cred *cred = (struct cred *) _cred;
if (cred) { validate_creds(cred); - if (atomic_dec_and_test(&(cred)->usage)) + if (atomic_sub_and_test(nr, &cred->usage)) __put_cred(cred); } }
+/* + * put_cred - Release a reference to a set of credentials + * @cred: The credentials to release + * + * Release a reference to a set of credentials, deleting them when the last ref + * is released. If %NULL is passed, nothing is done. + */ +static inline void put_cred(const struct cred *cred) +{ + put_cred_many(cred, 1); +} + /** * current_cred - Access the current task's subjective credentials * diff --git a/kernel/cred.c b/kernel/cred.c index 98cb4eca23fb..9398e534b997 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -162,23 +162,29 @@ EXPORT_SYMBOL(__put_cred); */ void exit_creds(struct task_struct *tsk) { - struct cred *cred; + struct cred *real_cred, *cred;
kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred, atomic_read(&tsk->cred->usage), read_cred_subscribers(tsk->cred));
- cred = (struct cred *) tsk->real_cred; + real_cred = (struct cred *) tsk->real_cred; tsk->real_cred = NULL; - validate_creds(cred); - alter_cred_subscribers(cred, -1); - put_cred(cred);
cred = (struct cred *) tsk->cred; tsk->cred = NULL; + validate_creds(cred); - alter_cred_subscribers(cred, -1); - put_cred(cred); + if (real_cred == cred) { + alter_cred_subscribers(cred, -2); + put_cred_many(cred, 2); + } else { + validate_creds(real_cred); + alter_cred_subscribers(real_cred, -1); + put_cred(real_cred); + alter_cred_subscribers(cred, -1); + put_cred(cred); + }
#ifdef CONFIG_KEYS_REQUEST_CACHE key_put(tsk->cached_requested_key); @@ -355,8 +361,7 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags) #endif clone_flags & CLONE_THREAD ) { - p->real_cred = get_cred(p->cred); - get_cred(p->cred); + p->real_cred = get_cred_many(p->cred, 2); alter_cred_subscribers(p->cred, 2); kdebug("share_creds(%p{%d,%d})", p->cred, atomic_read(&p->cred->usage), @@ -520,8 +525,7 @@ int commit_creds(struct cred *new) proc_id_connector(task, PROC_EVENT_GID);
/* release the old obj and subj refs both */ - put_cred(old); - put_cred(old); + put_cred_many(old, 2); return 0; } EXPORT_SYMBOL(commit_creds);