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Subject[PATCH 09/24] CRED: Detach the credentials from task_struct [ver #7]
Date
Detach the credentials from task_struct, duplicating them in copy_process()
and releasing them in __put_task_struct().

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
---
include/linux/cred.h | 29 ++++++++++++++
include/linux/init_task.h | 16 -------
include/linux/sched.h | 1
include/linux/security.h | 26 ++++++------
kernel/Makefile | 2 -
kernel/cred.c | 94 ++++++++++++++++++++++++++++++++++++++++++++
kernel/fork.c | 24 +++--------
security/capability.c | 8 ++--
security/security.c | 8 ++--
security/selinux/hooks.c | 32 +++++++--------
security/smack/smack_lsm.c | 20 +++++----
11 files changed, 177 insertions(+), 83 deletions(-)
create mode 100644 kernel/cred.c

diff --git a/include/linux/cred.h b/include/linux/cred.h
index 17ad725..a0fefc0 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -158,4 +158,33 @@ do { \
*(_gid) = current->cred->fsgid; \
} while(0)

+extern void __put_cred(struct cred *);
+extern int copy_creds(struct task_struct *, unsigned long);
+
+/**
+ * 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.
+ */
+static inline struct cred *get_cred(struct cred *cred)
+{
+ atomic_inc(&cred->usage);
+ return 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.
+ */
+static inline void put_cred(struct cred *cred)
+{
+ if (atomic_dec_and_test(&(cred)->usage))
+ __put_cred(cred);
+}
+
#endif /* _LINUX_CRED_H */
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 0abd837..234c24a 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -115,19 +115,6 @@ extern struct group_info init_groups;

extern struct cred init_cred;

-#define INIT_CRED(p) \
-{ \
- .usage = ATOMIC_INIT(3), \
- .securebits = SECUREBITS_DEFAULT, \
- .cap_inheritable = CAP_INIT_INH_SET, \
- .cap_permitted = CAP_FULL_SET, \
- .cap_effective = CAP_INIT_EFF_SET, \
- .cap_bset = CAP_INIT_BSET, \
- .user = INIT_USER, \
- .group_info = &init_groups, \
- .lock = __SPIN_LOCK_UNLOCKED(p.lock), \
-}
-
/*
* INIT_TASK is used to set up the first task table, touch at
* your own risk!. Base=0, limit=0x1fffff (=2MB)
@@ -162,8 +149,7 @@ extern struct cred init_cred;
.children = LIST_HEAD_INIT(tsk.children), \
.sibling = LIST_HEAD_INIT(tsk.sibling), \
.group_leader = &tsk, \
- .__temp_cred = INIT_CRED(tsk.__temp_cred), \
- .cred = &tsk.__temp_cred, \
+ .cred = &init_cred, \
.comm = "swapper", \
.thread = INIT_THREAD, \
.fs = &init_fs, \
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 304ede6..041b153 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1109,7 +1109,6 @@ struct task_struct {
struct list_head cpu_timers[3];

/* process credentials */
- struct cred __temp_cred __deprecated; /* temporary credentials to be removed */
struct cred *cred; /* actual/objective task credentials */

char comm[TASK_COMM_LEN]; /* executable name excluding path
diff --git a/include/linux/security.h b/include/linux/security.h
index c3eed5a..a0f5886 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -589,15 +589,15 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* manual page for definitions of the @clone_flags.
* @clone_flags contains the flags indicating what should be shared.
* Return 0 if permission is granted.
- * @task_alloc_security:
- * @p contains the task_struct for child process.
- * Allocate and attach a security structure to the p->security field. The
- * security field is initialized to NULL when the task structure is
+ * @cred_alloc_security:
+ * @cred contains the cred struct for child process.
+ * Allocate and attach a security structure to the cred->security field.
+ * The security field is initialized to NULL when the task structure is
* allocated.
* Return 0 if operation was successful.
- * @task_free_security:
- * @p contains the task_struct for process.
- * Deallocate and clear the p->security field.
+ * @cred_free:
+ * @cred points to the credentials.
+ * Deallocate and clear the cred->security field in a set of credentials.
* @task_setuid:
* Check permission before setting one or more of the user identity
* attributes of the current process. The @flags parameter indicates
@@ -1401,8 +1401,8 @@ struct security_operations {
int (*dentry_open) (struct file *file);

int (*task_create) (unsigned long clone_flags);
- int (*task_alloc_security) (struct task_struct *p);
- void (*task_free_security) (struct task_struct *p);
+ int (*cred_alloc_security) (struct cred *cred);
+ void (*cred_free) (struct cred *cred);
int (*task_setuid) (uid_t id0, uid_t id1, uid_t id2, int flags);
int (*task_post_setuid) (uid_t old_ruid /* or fsuid */ ,
uid_t old_euid, uid_t old_suid, int flags);
@@ -1659,8 +1659,8 @@ int security_file_send_sigiotask(struct task_struct *tsk,
int security_file_receive(struct file *file);
int security_dentry_open(struct file *file);
int security_task_create(unsigned long clone_flags);
-int security_task_alloc(struct task_struct *p);
-void security_task_free(struct task_struct *p);
+int security_cred_alloc(struct cred *cred);
+void security_cred_free(struct cred *cred);
int security_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags);
int security_task_post_setuid(uid_t old_ruid, uid_t old_euid,
uid_t old_suid, int flags);
@@ -2170,12 +2170,12 @@ static inline int security_task_create(unsigned long clone_flags)
return 0;
}

-static inline int security_task_alloc(struct task_struct *p)
+static inline int security_cred_alloc(struct cred *cred)
{
return 0;
}

-static inline void security_task_free(struct task_struct *p)
+static inline void security_cred_free(struct cred *cred)
{ }

static inline int security_task_setuid(uid_t id0, uid_t id1, uid_t id2,
diff --git a/kernel/Makefile b/kernel/Makefile
index 4e1d7df..8e6ab9c 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -9,7 +9,7 @@ obj-y = sched.o fork.o exec_domain.o panic.o printk.o \
rcupdate.o extable.o params.o posix-timers.o \
kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
- notifier.o ksysfs.o pm_qos_params.o sched_clock.o
+ notifier.o ksysfs.o pm_qos_params.o sched_clock.o cred.o

CFLAGS_REMOVE_sched.o = -mno-spe

diff --git a/kernel/cred.c b/kernel/cred.c
new file mode 100644
index 0000000..2195841
--- /dev/null
+++ b/kernel/cred.c
@@ -0,0 +1,94 @@
+/* Task credentials management
+ *
+ * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+#include <linux/module.h>
+#include <linux/cred.h>
+#include <linux/sched.h>
+#include <linux/key.h>
+#include <linux/keyctl.h>
+#include <linux/init_task.h>
+#include <linux/security.h>
+
+/*
+ * The initial credentials for the initial task
+ */
+struct cred init_cred = {
+ .usage = ATOMIC_INIT(3),
+ .securebits = SECUREBITS_DEFAULT,
+ .cap_inheritable = CAP_INIT_INH_SET,
+ .cap_permitted = CAP_FULL_SET,
+ .cap_effective = CAP_INIT_EFF_SET,
+ .cap_bset = CAP_INIT_BSET,
+ .user = INIT_USER,
+ .group_info = &init_groups,
+};
+
+/*
+ * The RCU callback to actually dispose of a set of credentials
+ */
+static void put_cred_rcu(struct rcu_head *rcu)
+{
+ struct cred *cred = container_of(rcu, struct cred, rcu);
+
+ BUG_ON(atomic_read(&cred->usage) != 0);
+
+ key_put(cred->thread_keyring);
+ key_put(cred->request_key_auth);
+ put_group_info(cred->group_info);
+ free_uid(cred->user);
+ security_cred_free(cred);
+ kfree(cred);
+}
+
+/**
+ * __put_cred - Destroy a set of credentials
+ * @sec: The record to release
+ *
+ * Destroy a set of credentials on which no references remain.
+ */
+void __put_cred(struct cred *cred)
+{
+ call_rcu(&cred->rcu, put_cred_rcu);
+}
+EXPORT_SYMBOL(__put_cred);
+
+/*
+ * Copy credentials for the new process created by fork()
+ */
+int copy_creds(struct task_struct *p, unsigned long clone_flags)
+{
+ struct cred *pcred;
+ int ret;
+
+ pcred = kmemdup(p->cred, sizeof(*p->cred), GFP_KERNEL);
+ if (!pcred)
+ return -ENOMEM;
+
+#ifdef CONFIG_SECURITY
+ pcred->security = NULL;
+#endif
+
+ ret = security_cred_alloc(pcred);
+ if (ret < 0) {
+ kfree(pcred);
+ return ret;
+ }
+
+ atomic_set(&pcred->usage, 1);
+ get_group_info(pcred->group_info);
+ get_uid(pcred->user);
+ key_get(pcred->thread_keyring);
+ key_get(pcred->request_key_auth);
+
+ /* RCU assignment is unneeded here as no-one can have accessed this
+ * pointer yet, barring us */
+ p->cred = pcred;
+ return 0;
+}
diff --git a/kernel/fork.c b/kernel/fork.c
index be0c716..8993a45 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -145,9 +145,7 @@ void __put_task_struct(struct task_struct *tsk)
WARN_ON(atomic_read(&tsk->usage));
WARN_ON(tsk == current);

- security_task_free(tsk);
- free_uid(tsk->__temp_cred.user);
- put_group_info(tsk->__temp_cred.group_info);
+ put_cred(tsk->cred);
delayacct_tsk_free(tsk);

if (!profile_handoff_task(tsk))
@@ -938,7 +936,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);
DEBUG_LOCKS_WARN_ON(!p->softirqs_enabled);
#endif
- p->cred = &p->__temp_cred;
retval = -EAGAIN;
if (atomic_read(&p->cred->user->processes) >=
p->signal->rlim[RLIMIT_NPROC].rlim_cur) {
@@ -947,9 +944,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
goto bad_fork_free;
}

- atomic_inc(&p->cred->user->__count);
- atomic_inc(&p->cred->user->processes);
- get_group_info(p->cred->group_info);
+ retval = copy_creds(p, clone_flags);
+ if (retval < 0)
+ goto bad_fork_free;

/*
* If multiple threads are within copy_process(), then this check
@@ -1007,9 +1004,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
do_posix_clock_monotonic_gettime(&p->start_time);
p->real_start_time = p->start_time;
monotonic_to_bootbased(&p->real_start_time);
-#ifdef CONFIG_SECURITY
- p->cred->security = NULL;
-#endif
p->io_context = NULL;
p->audit_context = NULL;
cgroup_fork(p);
@@ -1054,10 +1048,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
/* Perform scheduler related setup. Assign this task to a CPU. */
sched_fork(p, clone_flags);

- if ((retval = security_task_alloc(p)))
- goto bad_fork_cleanup_policy;
if ((retval = audit_alloc(p)))
- goto bad_fork_cleanup_security;
+ goto bad_fork_cleanup_policy;
/* copy all the process information */
if ((retval = copy_semundo(clone_flags, p)))
goto bad_fork_cleanup_audit;
@@ -1270,8 +1262,6 @@ bad_fork_cleanup_semundo:
exit_sem(p);
bad_fork_cleanup_audit:
audit_free(p);
-bad_fork_cleanup_security:
- security_task_free(p);
bad_fork_cleanup_policy:
#ifdef CONFIG_NUMA
mpol_put(p->mempolicy);
@@ -1284,9 +1274,7 @@ bad_fork_cleanup_cgroup:
bad_fork_cleanup_put_domain:
module_put(task_thread_info(p)->exec_domain->module);
bad_fork_cleanup_count:
- put_group_info(p->cred->group_info);
- atomic_dec(&p->cred->user->processes);
- free_uid(p->cred->user);
+ put_cred(p->cred);
bad_fork_free:
free_task(p);
fork_out:
diff --git a/security/capability.c b/security/capability.c
index 2458748..6c4b513 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -340,12 +340,12 @@ static int cap_task_create(unsigned long clone_flags)
return 0;
}

-static int cap_task_alloc_security(struct task_struct *p)
+static int cap_cred_alloc_security(struct cred *cred)
{
return 0;
}

-static void cap_task_free_security(struct task_struct *p)
+static void cap_cred_free(struct cred *cred)
{
}

@@ -890,8 +890,8 @@ void security_fixup_ops(struct security_operations *ops)
set_to_cap_if_null(ops, file_receive);
set_to_cap_if_null(ops, dentry_open);
set_to_cap_if_null(ops, task_create);
- set_to_cap_if_null(ops, task_alloc_security);
- set_to_cap_if_null(ops, task_free_security);
+ set_to_cap_if_null(ops, cred_alloc_security);
+ set_to_cap_if_null(ops, cred_free);
set_to_cap_if_null(ops, task_setuid);
set_to_cap_if_null(ops, task_post_setuid);
set_to_cap_if_null(ops, task_setgid);
diff --git a/security/security.c b/security/security.c
index c2203f5..23c3c91 100644
--- a/security/security.c
+++ b/security/security.c
@@ -602,14 +602,14 @@ int security_task_create(unsigned long clone_flags)
return security_ops->task_create(clone_flags);
}

-int security_task_alloc(struct task_struct *p)
+int security_cred_alloc(struct cred *cred)
{
- return security_ops->task_alloc_security(p);
+ return security_ops->cred_alloc_security(cred);
}

-void security_task_free(struct task_struct *p)
+void security_cred_free(struct cred *cred)
{
- security_ops->task_free_security(p);
+ security_ops->cred_free(cred);
}

int security_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3e8900e..1efc990 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -157,7 +157,7 @@ static int selinux_secmark_enabled(void)

/* Allocate and free functions for each kind of security blob. */

-static int task_alloc_security(struct task_struct *task)
+static int cred_alloc_security(struct cred *cred)
{
struct task_security_struct *tsec;

@@ -166,18 +166,11 @@ static int task_alloc_security(struct task_struct *task)
return -ENOMEM;

tsec->osid = tsec->sid = SECINITSID_UNLABELED;
- task->cred->security = tsec;
+ cred->security = tsec;

return 0;
}

-static void task_free_security(struct task_struct *task)
-{
- struct task_security_struct *tsec = task->cred->security;
- task->cred->security = NULL;
- kfree(tsec);
-}
-
static int inode_alloc_security(struct inode *inode)
{
struct task_security_struct *tsec = current->cred->security;
@@ -3188,17 +3181,17 @@ static int selinux_task_create(unsigned long clone_flags)
return task_has_perm(current, current, PROCESS__FORK);
}

-static int selinux_task_alloc_security(struct task_struct *tsk)
+static int selinux_cred_alloc_security(struct cred *cred)
{
struct task_security_struct *tsec1, *tsec2;
int rc;

tsec1 = current->cred->security;

- rc = task_alloc_security(tsk);
+ rc = cred_alloc_security(cred);
if (rc)
return rc;
- tsec2 = tsk->cred->security;
+ tsec2 = cred->security;

tsec2->osid = tsec1->osid;
tsec2->sid = tsec1->sid;
@@ -3212,9 +3205,14 @@ static int selinux_task_alloc_security(struct task_struct *tsk)
return 0;
}

-static void selinux_task_free_security(struct task_struct *tsk)
+/*
+ * detach and free the LSM part of a set of credentials
+ */
+static void selinux_cred_free(struct cred *cred)
{
- task_free_security(tsk);
+ struct task_security_struct *tsec = cred->security;
+ cred->security = NULL;
+ kfree(tsec);
}

static int selinux_task_setuid(uid_t id0, uid_t id1, uid_t id2, int flags)
@@ -5446,8 +5444,8 @@ static struct security_operations selinux_ops = {
.dentry_open = selinux_dentry_open,

.task_create = selinux_task_create,
- .task_alloc_security = selinux_task_alloc_security,
- .task_free_security = selinux_task_free_security,
+ .cred_alloc_security = selinux_cred_alloc_security,
+ .cred_free = selinux_cred_free,
.task_setuid = selinux_task_setuid,
.task_post_setuid = selinux_task_post_setuid,
.task_setgid = selinux_task_setgid,
@@ -5577,7 +5575,7 @@ static __init int selinux_init(void)
printk(KERN_INFO "SELinux: Initializing.\n");

/* Set the security state for the initial task. */
- if (task_alloc_security(current))
+ if (cred_alloc_security(current->cred))
panic("SELinux: Failed to initialize initial task.\n");
tsec = current->cred->security;
tsec->osid = tsec->sid = SECINITSID_KERNEL;
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index ccded56..7da592f 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -975,8 +975,8 @@ static int smack_file_receive(struct file *file)
*/

/**
- * smack_task_alloc_security - "allocate" a task blob
- * @tsk: the task in need of a blob
+ * smack_cred_alloc_security - "allocate" a task cred blob
+ * @cred: the task creds in need of a blob
*
* Smack isn't using copies of blobs. Everyone
* points to an immutable list. No alloc required.
@@ -984,24 +984,24 @@ static int smack_file_receive(struct file *file)
*
* Always returns 0
*/
-static int smack_task_alloc_security(struct task_struct *tsk)
+static int smack_cred_alloc_security(struct cred *cred)
{
- tsk->cred->security = current->cred->security;
+ cred->security = current->cred->security;

return 0;
}

/**
- * smack_task_free_security - "free" a task blob
- * @task: the task with the blob
+ * smack_cred_free - "free" task-level security credentials
+ * @cred: the credentials in question
*
* Smack isn't using copies of blobs. Everyone
* points to an immutable list. The blobs never go away.
* There is no leak here.
*/
-static void smack_task_free_security(struct task_struct *task)
+static void smack_cred_free(struct cred *cred)
{
- task->cred->security = NULL;
+ cred->security = NULL;
}

/**
@@ -2627,8 +2627,8 @@ struct security_operations smack_ops = {
.file_send_sigiotask = smack_file_send_sigiotask,
.file_receive = smack_file_receive,

- .task_alloc_security = smack_task_alloc_security,
- .task_free_security = smack_task_free_security,
+ .cred_alloc_security = smack_cred_alloc_security,
+ .cred_free = smack_cred_free,
.task_post_setuid = cap_task_post_setuid,
.task_setpgid = smack_task_setpgid,
.task_getpgid = smack_task_getpgid,


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