Commit 41e84562 authored by Mateusz Guzik's avatar Mateusz Guzik Committed by Paul Moore
Browse files

cred: add get_cred_many and put_cred_many 



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: default avatarMateusz Guzik <mjguzik@gmail.com>
[PM: removed changelog from commit description]
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent 20a2aa47

include/linux/cred.h

+50 −9
Original line number Diff line number Diff line
@@ -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

 *

kernel/cred.c

+15 −11
Original line number Diff line number Diff line
@@ -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);

	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);