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Commit ec8e6a4e authored by Tetsuo Handa's avatar Tetsuo Handa Committed by James Morris
Browse files

TOMOYO: Add refcounter on domain structure. 



Add refcounter to "struct tomoyo_domain_info" since garbage collector needs to
determine whether this struct is referred by "struct cred"->security or not.

Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
Signed-off-by: default avatarJames Morris <jmorris@namei.org>
parent 76bb0895

security/tomoyo/common.h

+5 −0
Original line number Diff line number Diff line
@@ -234,6 +234,10 @@ struct tomoyo_acl_info { 
 *      name of the domain to be created was too long or it could not allocate

 *      memory. If set to true, more than one process continued execve()

 *      without domain transition.

 *  (9) "users" is an atomic_t that holds how many "struct cred"->security

 *      are referring this "struct tomoyo_domain_info". If is_deleted == true

 *      and users == 0, this struct will be kfree()d upon next garbage

 *      collection.

 *

 * A domain's lifecycle is an analogy of files on / directory.

 * Multiple domains with the same domainname cannot be created (as with
@@ -252,6 +256,7 @@ struct tomoyo_domain_info { 
	bool quota_warned; /* Quota warnning flag.   */

	bool ignore_global_allow_read; /* Ignore "allow_read" flag. */

	bool transition_failed; /* Domain transition failed flag. */

	atomic_t users; /* Number of referring credentials. */

};



/*

security/tomoyo/domain.c

+2 −0
Original line number Diff line number Diff line
@@ -817,6 +817,8 @@ int tomoyo_find_next_domain(struct linux_binprm *bprm) 
 out:

	if (!domain)

		domain = old_domain;

	/* Update reference count on "struct tomoyo_domain_info". */

	atomic_inc(&domain->users);

	bprm->cred->security = domain;

	kfree(real_program_name);

	kfree(symlink_program_name);

security/tomoyo/tomoyo.c

+21 −16
Original line number Diff line number Diff line
@@ -21,21 +21,23 @@ static int tomoyo_cred_alloc_blank(struct cred *new, gfp_t gfp) 
static int tomoyo_cred_prepare(struct cred *new, const struct cred *old,

			       gfp_t gfp)

{

	/*

	 * Since "struct tomoyo_domain_info *" is a sharable pointer,

	 * we don't need to duplicate.

	 */

	new->security = old->security;

	struct tomoyo_domain_info *domain = old->security;

	new->security = domain;

	if (domain)

		atomic_inc(&domain->users);

	return 0;

}



static void tomoyo_cred_transfer(struct cred *new, const struct cred *old)

{

	/*

	 * Since "struct tomoyo_domain_info *" is a sharable pointer,

	 * we don't need to duplicate.

	 */

	new->security = old->security;

	tomoyo_cred_prepare(new, old, 0);

}



static void tomoyo_cred_free(struct cred *cred)

{

	struct tomoyo_domain_info *domain = cred->security;

	if (domain)

		atomic_dec(&domain->users);

}



static int tomoyo_bprm_set_creds(struct linux_binprm *bprm)
@@ -58,6 +60,14 @@ static int tomoyo_bprm_set_creds(struct linux_binprm *bprm) 
	 */

	if (!tomoyo_policy_loaded)

		tomoyo_load_policy(bprm->filename);

	/*

	 * Release reference to "struct tomoyo_domain_info" stored inside

	 * "bprm->cred->security". New reference to "struct tomoyo_domain_info"

	 * stored inside "bprm->cred->security" will be acquired later inside

	 * tomoyo_find_next_domain().

	 */

	atomic_dec(&((struct tomoyo_domain_info *)

		     bprm->cred->security)->users);

	/*

	 * Tell tomoyo_bprm_check_security() is called for the first time of an

	 * execve operation.
@@ -75,12 +85,6 @@ static int tomoyo_bprm_check_security(struct linux_binprm *bprm) 
	 * using current domain.

	 */

	if (!domain) {

		/*

		 * We will need to protect whole execve() operation when GC

		 * starts kfree()ing "struct tomoyo_domain_info" because

		 * bprm->cred->security points to "struct tomoyo_domain_info"

		 * but "struct tomoyo_domain_info" does not have a refcounter.

		 */

		const int idx = tomoyo_read_lock();

		const int err = tomoyo_find_next_domain(bprm);

		tomoyo_read_unlock(idx);
@@ -265,6 +269,7 @@ static struct security_operations tomoyo_security_ops = { 
	.cred_alloc_blank    = tomoyo_cred_alloc_blank,

	.cred_prepare        = tomoyo_cred_prepare,

	.cred_transfer	     = tomoyo_cred_transfer,

	.cred_free           = tomoyo_cred_free,

	.bprm_set_creds      = tomoyo_bprm_set_creds,

	.bprm_check_security = tomoyo_bprm_check_security,

	.file_fcntl          = tomoyo_file_fcntl,