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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: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Acked-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: James Morris <jmorris@namei.org>
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@ -234,6 +234,10 @@ struct tomoyo_acl_info {
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* name of the domain to be created was too long or it could not allocate
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* memory. If set to true, more than one process continued execve()
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* without domain transition.
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* (9) "users" is an atomic_t that holds how many "struct cred"->security
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* are referring this "struct tomoyo_domain_info". If is_deleted == true
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* and users == 0, this struct will be kfree()d upon next garbage
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* collection.
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*
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* A domain's lifecycle is an analogy of files on / directory.
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* Multiple domains with the same domainname cannot be created (as with
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@ -252,6 +256,7 @@ struct tomoyo_domain_info {
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bool quota_warned; /* Quota warnning flag. */
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bool ignore_global_allow_read; /* Ignore "allow_read" flag. */
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bool transition_failed; /* Domain transition failed flag. */
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atomic_t users; /* Number of referring credentials. */
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};
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/*
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@ -817,6 +817,8 @@ int tomoyo_find_next_domain(struct linux_binprm *bprm)
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out:
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if (!domain)
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domain = old_domain;
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/* Update reference count on "struct tomoyo_domain_info". */
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atomic_inc(&domain->users);
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bprm->cred->security = domain;
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kfree(real_program_name);
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kfree(symlink_program_name);
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@ -21,21 +21,23 @@ static int tomoyo_cred_alloc_blank(struct cred *new, gfp_t gfp)
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static int tomoyo_cred_prepare(struct cred *new, const struct cred *old,
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gfp_t gfp)
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{
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/*
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* Since "struct tomoyo_domain_info *" is a sharable pointer,
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* we don't need to duplicate.
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*/
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new->security = old->security;
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struct tomoyo_domain_info *domain = old->security;
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new->security = domain;
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if (domain)
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atomic_inc(&domain->users);
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return 0;
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}
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static void tomoyo_cred_transfer(struct cred *new, const struct cred *old)
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{
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/*
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* Since "struct tomoyo_domain_info *" is a sharable pointer,
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* we don't need to duplicate.
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*/
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new->security = old->security;
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tomoyo_cred_prepare(new, old, 0);
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}
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static void tomoyo_cred_free(struct cred *cred)
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{
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struct tomoyo_domain_info *domain = cred->security;
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if (domain)
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atomic_dec(&domain->users);
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}
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static int tomoyo_bprm_set_creds(struct linux_binprm *bprm)
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@ -58,6 +60,14 @@ static int tomoyo_bprm_set_creds(struct linux_binprm *bprm)
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*/
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if (!tomoyo_policy_loaded)
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tomoyo_load_policy(bprm->filename);
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/*
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* Release reference to "struct tomoyo_domain_info" stored inside
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* "bprm->cred->security". New reference to "struct tomoyo_domain_info"
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* stored inside "bprm->cred->security" will be acquired later inside
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* tomoyo_find_next_domain().
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*/
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atomic_dec(&((struct tomoyo_domain_info *)
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bprm->cred->security)->users);
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/*
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* Tell tomoyo_bprm_check_security() is called for the first time of an
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* execve operation.
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@ -75,12 +85,6 @@ static int tomoyo_bprm_check_security(struct linux_binprm *bprm)
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* using current domain.
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*/
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if (!domain) {
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/*
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* We will need to protect whole execve() operation when GC
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* starts kfree()ing "struct tomoyo_domain_info" because
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* bprm->cred->security points to "struct tomoyo_domain_info"
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* but "struct tomoyo_domain_info" does not have a refcounter.
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*/
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const int idx = tomoyo_read_lock();
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const int err = tomoyo_find_next_domain(bprm);
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tomoyo_read_unlock(idx);
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@ -265,6 +269,7 @@ static struct security_operations tomoyo_security_ops = {
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.cred_alloc_blank = tomoyo_cred_alloc_blank,
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.cred_prepare = tomoyo_cred_prepare,
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.cred_transfer = tomoyo_cred_transfer,
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.cred_free = tomoyo_cred_free,
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.bprm_set_creds = tomoyo_bprm_set_creds,
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.bprm_check_security = tomoyo_bprm_check_security,
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.file_fcntl = tomoyo_file_fcntl,
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