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TOMOYO: Add refcounter on domain structure.

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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>
This commit is contained in:
Tetsuo Handa 2010-02-11 09:43:20 +09:00 committed by James Morris
parent 76bb0895d0
commit ec8e6a4e06
3 changed files with 28 additions and 16 deletions
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5
security/tomoyo/common.h
View file

@ -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. */
};
/*

2
security/tomoyo/domain.c
View file

@ -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);

37
security/tomoyo/tomoyo.c
View file

@ -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,