CRED: Separate per-task-group keyrings from signal_struct
Separate per-task-group keyrings from signal_struct and dangle their anchor
from the cred struct rather than the signal_struct.
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 166ce4d..62b9e53 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -72,6 +72,21 @@
extern int in_egroup_p(gid_t);
/*
+ * The common credentials for a thread group
+ * - shared by CLONE_THREAD
+ */
+#ifdef CONFIG_KEYS
+struct thread_group_cred {
+ atomic_t usage;
+ pid_t tgid; /* thread group process ID */
+ spinlock_t lock;
+ struct key *session_keyring; /* keyring inherited over fork */
+ struct key *process_keyring; /* keyring private to this process */
+ struct rcu_head rcu; /* RCU deletion hook */
+};
+#endif
+
+/*
* The security context of a task
*
* The parts of the context break down into two categories:
@@ -114,6 +129,7 @@
* keys to */
struct key *thread_keyring; /* keyring private to this thread */
struct key *request_key_auth; /* assumed request_key authority */
+ struct thread_group_cred *tgcred; /* thread-group shared credentials */
#endif
#ifdef CONFIG_SECURITY
void *security; /* subjective LSM security */
diff --git a/include/linux/key.h b/include/linux/key.h
index df709e1..0836cc8 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -278,9 +278,7 @@
*/
extern void switch_uid_keyring(struct user_struct *new_user);
extern int copy_keys(unsigned long clone_flags, struct task_struct *tsk);
-extern int copy_thread_group_keys(struct task_struct *tsk);
extern void exit_keys(struct task_struct *tsk);
-extern void exit_thread_group_keys(struct signal_struct *tg);
extern int suid_keys(struct task_struct *tsk);
extern int exec_keys(struct task_struct *tsk);
extern void key_fsuid_changed(struct task_struct *tsk);
@@ -289,8 +287,8 @@
#define __install_session_keyring(keyring) \
({ \
- struct key *old_session = current->signal->session_keyring; \
- current->signal->session_keyring = keyring; \
+ struct key *old_session = current->cred->tgcred->session_keyring; \
+ current->cred->tgcred->session_keyring = keyring; \
old_session; \
})
@@ -308,9 +306,7 @@
#define switch_uid_keyring(u) do { } while(0)
#define __install_session_keyring(k) ({ NULL; })
#define copy_keys(f,t) 0
-#define copy_thread_group_keys(t) 0
#define exit_keys(t) do { } while(0)
-#define exit_thread_group_keys(tg) do { } while(0)
#define suid_keys(t) do { } while(0)
#define exec_keys(t) do { } while(0)
#define key_fsuid_changed(t) do { } while(0)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 740cf94..2913252 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -571,12 +571,6 @@
*/
struct rlimit rlim[RLIM_NLIMITS];
- /* keep the process-shared keyrings here so that they do the right
- * thing in threads created with CLONE_THREAD */
-#ifdef CONFIG_KEYS
- struct key *session_keyring; /* keyring inherited over fork */
- struct key *process_keyring; /* keyring private to this process */
-#endif
#ifdef CONFIG_BSD_PROCESS_ACCT
struct pacct_struct pacct; /* per-process accounting information */
#endif
diff --git a/kernel/cred.c b/kernel/cred.c
index 833244a..ac73e36 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -17,6 +17,17 @@
#include <linux/security.h>
/*
+ * The common credentials for the initial task's thread group
+ */
+#ifdef CONFIG_KEYS
+static struct thread_group_cred init_tgcred = {
+ .usage = ATOMIC_INIT(2),
+ .tgid = 0,
+ .lock = SPIN_LOCK_UNLOCKED,
+};
+#endif
+
+/*
* The initial credentials for the initial task
*/
struct cred init_cred = {
@@ -28,9 +39,42 @@
.cap_bset = CAP_INIT_BSET,
.user = INIT_USER,
.group_info = &init_groups,
+#ifdef CONFIG_KEYS
+ .tgcred = &init_tgcred,
+#endif
};
/*
+ * Dispose of the shared task group credentials
+ */
+#ifdef CONFIG_KEYS
+static void release_tgcred_rcu(struct rcu_head *rcu)
+{
+ struct thread_group_cred *tgcred =
+ container_of(rcu, struct thread_group_cred, rcu);
+
+ BUG_ON(atomic_read(&tgcred->usage) != 0);
+
+ key_put(tgcred->session_keyring);
+ key_put(tgcred->process_keyring);
+ kfree(tgcred);
+}
+#endif
+
+/*
+ * Release a set of thread group credentials.
+ */
+static void release_tgcred(struct cred *cred)
+{
+#ifdef CONFIG_KEYS
+ struct thread_group_cred *tgcred = cred->tgcred;
+
+ if (atomic_dec_and_test(&tgcred->usage))
+ call_rcu(&tgcred->rcu, release_tgcred_rcu);
+#endif
+}
+
+/*
* The RCU callback to actually dispose of a set of credentials
*/
static void put_cred_rcu(struct rcu_head *rcu)
@@ -41,6 +85,7 @@
key_put(cred->thread_keyring);
key_put(cred->request_key_auth);
+ release_tgcred(cred);
put_group_info(cred->group_info);
free_uid(cred->user);
security_cred_free(cred);
@@ -71,12 +116,30 @@
if (!pcred)
return -ENOMEM;
+#ifdef CONFIG_KEYS
+ if (clone_flags & CLONE_THREAD) {
+ atomic_inc(&pcred->tgcred->usage);
+ } else {
+ pcred->tgcred = kmalloc(sizeof(struct cred), GFP_KERNEL);
+ if (!pcred->tgcred) {
+ kfree(pcred);
+ return -ENOMEM;
+ }
+ atomic_set(&pcred->tgcred->usage, 1);
+ spin_lock_init(&pcred->tgcred->lock);
+ pcred->tgcred->process_keyring = NULL;
+ pcred->tgcred->session_keyring =
+ key_get(p->cred->tgcred->session_keyring);
+ }
+#endif
+
#ifdef CONFIG_SECURITY
pcred->security = NULL;
#endif
ret = security_cred_alloc(pcred);
if (ret < 0) {
+ release_tgcred(pcred);
kfree(pcred);
return ret;
}
diff --git a/kernel/fork.c b/kernel/fork.c
index c932e28..ded1972 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -802,12 +802,6 @@
if (!sig)
return -ENOMEM;
- ret = copy_thread_group_keys(tsk);
- if (ret < 0) {
- kmem_cache_free(signal_cachep, sig);
- return ret;
- }
-
atomic_set(&sig->count, 1);
atomic_set(&sig->live, 1);
init_waitqueue_head(&sig->wait_chldexit);
@@ -852,7 +846,6 @@
void __cleanup_signal(struct signal_struct *sig)
{
thread_group_cputime_free(sig);
- exit_thread_group_keys(sig);
tty_kref_put(sig->tty);
kmem_cache_free(signal_cachep, sig);
}
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index 212601e..70ee934 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -189,7 +189,7 @@
might_sleep();
- if (!tsk->signal->process_keyring) {
+ if (!tsk->cred->tgcred->process_keyring) {
sprintf(buf, "_pid.%u", tsk->tgid);
keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk,
@@ -200,12 +200,12 @@
}
/* attach keyring */
- spin_lock_irq(&tsk->sighand->siglock);
- if (!tsk->signal->process_keyring) {
- tsk->signal->process_keyring = keyring;
+ spin_lock_irq(&tsk->cred->tgcred->lock);
+ if (!tsk->cred->tgcred->process_keyring) {
+ tsk->cred->tgcred->process_keyring = keyring;
keyring = NULL;
}
- spin_unlock_irq(&tsk->sighand->siglock);
+ spin_unlock_irq(&tsk->cred->tgcred->lock);
key_put(keyring);
}
@@ -235,11 +235,11 @@
sprintf(buf, "_ses.%u", tsk->tgid);
flags = KEY_ALLOC_QUOTA_OVERRUN;
- if (tsk->signal->session_keyring)
+ if (tsk->cred->tgcred->session_keyring)
flags = KEY_ALLOC_IN_QUOTA;
- keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk,
- flags, NULL);
+ keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid,
+ tsk, flags, NULL);
if (IS_ERR(keyring))
return PTR_ERR(keyring);
}
@@ -248,10 +248,10 @@
}
/* install the keyring */
- spin_lock_irq(&tsk->sighand->siglock);
- old = tsk->signal->session_keyring;
- rcu_assign_pointer(tsk->signal->session_keyring, keyring);
- spin_unlock_irq(&tsk->sighand->siglock);
+ spin_lock_irq(&tsk->cred->tgcred->lock);
+ old = tsk->cred->tgcred->session_keyring;
+ rcu_assign_pointer(tsk->cred->tgcred->session_keyring, keyring);
+ spin_unlock_irq(&tsk->cred->tgcred->lock);
/* we're using RCU on the pointer, but there's no point synchronising
* on it if it didn't previously point to anything */
@@ -266,28 +266,6 @@
/*****************************************************************************/
/*
- * copy the keys in a thread group for fork without CLONE_THREAD
- */
-int copy_thread_group_keys(struct task_struct *tsk)
-{
- key_check(current->thread_group->session_keyring);
- key_check(current->thread_group->process_keyring);
-
- /* no process keyring yet */
- tsk->signal->process_keyring = NULL;
-
- /* same session keyring */
- rcu_read_lock();
- tsk->signal->session_keyring =
- key_get(rcu_dereference(current->signal->session_keyring));
- rcu_read_unlock();
-
- return 0;
-
-} /* end copy_thread_group_keys() */
-
-/*****************************************************************************/
-/*
* copy the keys for fork
*/
int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
@@ -307,17 +285,6 @@
/*****************************************************************************/
/*
- * dispose of thread group keys upon thread group destruction
- */
-void exit_thread_group_keys(struct signal_struct *tg)
-{
- key_put(tg->session_keyring);
- key_put(tg->process_keyring);
-
-} /* end exit_thread_group_keys() */
-
-/*****************************************************************************/
-/*
* dispose of per-thread keys upon thread exit
*/
void exit_keys(struct task_struct *tsk)
@@ -344,10 +311,10 @@
key_put(old);
/* discard the process keyring from a newly exec'd task */
- spin_lock_irq(&tsk->sighand->siglock);
- old = tsk->signal->process_keyring;
- tsk->signal->process_keyring = NULL;
- spin_unlock_irq(&tsk->sighand->siglock);
+ spin_lock_irq(&tsk->cred->tgcred->lock);
+ old = tsk->cred->tgcred->process_keyring;
+ tsk->cred->tgcred->process_keyring = NULL;
+ spin_unlock_irq(&tsk->cred->tgcred->lock);
key_put(old);
@@ -452,9 +419,9 @@
}
/* search the process keyring second */
- if (context->signal->process_keyring) {
+ if (cred->tgcred->process_keyring) {
key_ref = keyring_search_aux(
- make_key_ref(context->signal->process_keyring, 1),
+ make_key_ref(cred->tgcred->process_keyring, 1),
context, type, description, match);
if (!IS_ERR(key_ref))
goto found;
@@ -473,11 +440,11 @@
}
/* search the session keyring */
- if (context->signal->session_keyring) {
+ if (cred->tgcred->session_keyring) {
rcu_read_lock();
key_ref = keyring_search_aux(
make_key_ref(rcu_dereference(
- context->signal->session_keyring),
+ cred->tgcred->session_keyring),
1),
context, type, description, match);
rcu_read_unlock();
@@ -586,11 +553,13 @@
{
struct request_key_auth *rka;
struct task_struct *t = current;
- struct cred *cred = current_cred();
+ struct cred *cred;
struct key *key;
key_ref_t key_ref, skey_ref;
int ret;
+try_again:
+ cred = get_current_cred();
key_ref = ERR_PTR(-ENOKEY);
switch (id) {
@@ -604,6 +573,7 @@
key = ERR_PTR(ret);
goto error;
}
+ goto reget_creds;
}
key = cred->thread_keyring;
@@ -612,7 +582,7 @@
break;
case KEY_SPEC_PROCESS_KEYRING:
- if (!t->signal->process_keyring) {
+ if (!cred->tgcred->process_keyring) {
if (!create)
goto error;
@@ -621,15 +591,16 @@
key = ERR_PTR(ret);
goto error;
}
+ goto reget_creds;
}
- key = t->signal->process_keyring;
+ key = cred->tgcred->process_keyring;
atomic_inc(&key->usage);
key_ref = make_key_ref(key, 1);
break;
case KEY_SPEC_SESSION_KEYRING:
- if (!t->signal->session_keyring) {
+ if (!cred->tgcred->session_keyring) {
/* always install a session keyring upon access if one
* doesn't exist yet */
ret = install_user_keyrings();
@@ -639,10 +610,11 @@
cred->user->session_keyring);
if (ret < 0)
goto error;
+ goto reget_creds;
}
rcu_read_lock();
- key = rcu_dereference(t->signal->session_keyring);
+ key = rcu_dereference(cred->tgcred->session_keyring);
atomic_inc(&key->usage);
rcu_read_unlock();
key_ref = make_key_ref(key, 1);
@@ -758,6 +730,7 @@
goto invalid_key;
error:
+ put_cred(cred);
return key_ref;
invalid_key:
@@ -765,6 +738,12 @@
key_ref = ERR_PTR(ret);
goto error;
+ /* if we attempted to install a keyring, then it may have caused new
+ * creds to be installed */
+reget_creds:
+ put_cred(cred);
+ goto try_again;
+
} /* end lookup_user_key() */
/*****************************************************************************/
@@ -777,6 +756,7 @@
long join_session_keyring(const char *name)
{
struct task_struct *tsk = current;
+ struct cred *cred = current->cred;
struct key *keyring;
long ret;
@@ -787,7 +767,7 @@
goto error;
rcu_read_lock();
- ret = rcu_dereference(tsk->signal->session_keyring)->serial;
+ ret = rcu_dereference(cred->tgcred->session_keyring)->serial;
rcu_read_unlock();
goto error;
}
@@ -799,7 +779,7 @@
keyring = find_keyring_by_name(name, false);
if (PTR_ERR(keyring) == -ENOKEY) {
/* not found - try and create a new one */
- keyring = keyring_alloc(name, tsk->cred->uid, tsk->cred->gid, tsk,
+ keyring = keyring_alloc(name, cred->uid, cred->gid, tsk,
KEY_ALLOC_IN_QUOTA, NULL);
if (IS_ERR(keyring)) {
ret = PTR_ERR(keyring);
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 0488b0a..3d12558 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -66,7 +66,6 @@
const char *op,
void *aux)
{
- struct task_struct *tsk = current;
const struct cred *cred = current_cred();
key_serial_t prkey, sskey;
struct key *key = cons->key, *authkey = cons->authkey, *keyring;
@@ -109,18 +108,13 @@
cred->thread_keyring->serial : 0);
prkey = 0;
- if (tsk->signal->process_keyring)
- prkey = tsk->signal->process_keyring->serial;
+ if (cred->tgcred->process_keyring)
+ prkey = cred->tgcred->process_keyring->serial;
- sprintf(keyring_str[1], "%d", prkey);
-
- if (tsk->signal->session_keyring) {
- rcu_read_lock();
- sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
- rcu_read_unlock();
- } else {
+ if (cred->tgcred->session_keyring)
+ sskey = rcu_dereference(cred->tgcred->session_keyring)->serial;
+ else
sskey = cred->user->session_keyring->serial;
- }
sprintf(keyring_str[2], "%d", sskey);
@@ -222,7 +216,7 @@
static void construct_get_dest_keyring(struct key **_dest_keyring)
{
struct request_key_auth *rka;
- struct task_struct *tsk = current;
+ const struct cred *cred = current_cred();
struct key *dest_keyring = *_dest_keyring, *authkey;
kenter("%p", dest_keyring);
@@ -234,11 +228,11 @@
} else {
/* use a default keyring; falling through the cases until we
* find one that we actually have */
- switch (tsk->cred->jit_keyring) {
+ switch (cred->jit_keyring) {
case KEY_REQKEY_DEFL_DEFAULT:
case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
- if (tsk->cred->request_key_auth) {
- authkey = tsk->cred->request_key_auth;
+ if (cred->request_key_auth) {
+ authkey = cred->request_key_auth;
down_read(&authkey->sem);
rka = authkey->payload.data;
if (!test_bit(KEY_FLAG_REVOKED,
@@ -251,19 +245,19 @@
}
case KEY_REQKEY_DEFL_THREAD_KEYRING:
- dest_keyring = key_get(tsk->cred->thread_keyring);
+ dest_keyring = key_get(cred->thread_keyring);
if (dest_keyring)
break;
case KEY_REQKEY_DEFL_PROCESS_KEYRING:
- dest_keyring = key_get(tsk->signal->process_keyring);
+ dest_keyring = key_get(cred->tgcred->process_keyring);
if (dest_keyring)
break;
case KEY_REQKEY_DEFL_SESSION_KEYRING:
rcu_read_lock();
dest_keyring = key_get(
- rcu_dereference(tsk->signal->session_keyring));
+ rcu_dereference(cred->tgcred->session_keyring));
rcu_read_unlock();
if (dest_keyring)
@@ -271,11 +265,11 @@
case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
dest_keyring =
- key_get(tsk->cred->user->session_keyring);
+ key_get(cred->user->session_keyring);
break;
case KEY_REQKEY_DEFL_USER_KEYRING:
- dest_keyring = key_get(tsk->cred->user->uid_keyring);
+ dest_keyring = key_get(cred->user->uid_keyring);
break;
case KEY_REQKEY_DEFL_GROUP_KEYRING: