[GitHub/mt8127/android_kernel_alcatel_ttab.git] / security / yama / yama_lsm.c

/*
 * Yama Linux Security Module
 *
 * Author: Kees Cook <keescook@chromium.org>
 *
 * Copyright (C) 2010 Canonical, Ltd.
 * Copyright (C) 2011 The Chromium OS Authors.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2, as
 * published by the Free Software Foundation.
 *
 */

#include <linux/security.h>
#include <linux/sysctl.h>
#include <linux/ptrace.h>
#include <linux/prctl.h>
#include <linux/ratelimit.h>
#include <linux/workqueue.h>

#define YAMA_SCOPE_DISABLED	0
#define YAMA_SCOPE_RELATIONAL	1
#define YAMA_SCOPE_CAPABILITY	2
#define YAMA_SCOPE_NO_ATTACH	3

static int ptrace_scope = YAMA_SCOPE_RELATIONAL;

/* describe a ptrace relationship for potential exception */
struct ptrace_relation {
	struct task_struct *tracer;
	struct task_struct *tracee;
	bool invalid;
	struct list_head node;
	struct rcu_head rcu;
};

static LIST_HEAD(ptracer_relations);
static DEFINE_SPINLOCK(ptracer_relations_lock);

static void yama_relation_cleanup(struct work_struct *work);
static DECLARE_WORK(yama_relation_work, yama_relation_cleanup);

/**
 * yama_relation_cleanup - remove invalid entries from the relation list
 *
 */
static void yama_relation_cleanup(struct work_struct *work)
{
	struct ptrace_relation *relation;

	spin_lock(&ptracer_relations_lock);
	rcu_read_lock();
	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
		if (relation->invalid) {
			list_del_rcu(&relation->node);
			kfree_rcu(relation, rcu);
		}
	}
	rcu_read_unlock();
	spin_unlock(&ptracer_relations_lock);
}

/**
 * yama_ptracer_add - add/replace an exception for this tracer/tracee pair
 * @tracer: the task_struct of the process doing the ptrace
 * @tracee: the task_struct of the process to be ptraced
 *
 * Each tracee can have, at most, one tracer registered. Each time this
 * is called, the prior registered tracer will be replaced for the tracee.
 *
 * Returns 0 if relationship was added, -ve on error.
 */
static int yama_ptracer_add(struct task_struct *tracer,
			    struct task_struct *tracee)
{
	struct ptrace_relation *relation, *added;

	added = kmalloc(sizeof(*added), GFP_KERNEL);
	if (!added)
		return -ENOMEM;

	added->tracee = tracee;
	added->tracer = tracer;
	added->invalid = false;

	spin_lock(&ptracer_relations_lock);
	rcu_read_lock();
	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
		if (relation->invalid)
			continue;
		if (relation->tracee == tracee) {
			list_replace_rcu(&relation->node, &added->node);
			kfree_rcu(relation, rcu);
			goto out;
		}
	}

	list_add_rcu(&added->node, &ptracer_relations);

out:
	rcu_read_unlock();
	spin_unlock(&ptracer_relations_lock);
	return 0;
}

/**
 * yama_ptracer_del - remove exceptions related to the given tasks
 * @tracer: remove any relation where tracer task matches
 * @tracee: remove any relation where tracee task matches
 */
static void yama_ptracer_del(struct task_struct *tracer,
			     struct task_struct *tracee)
{
	struct ptrace_relation *relation;
	bool marked = false;

	rcu_read_lock();
	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
		if (relation->invalid)
			continue;
		if (relation->tracee == tracee ||
		    (tracer && relation->tracer == tracer)) {
			relation->invalid = true;
			marked = true;
		}
	}
	rcu_read_unlock();

	if (marked)
		schedule_work(&yama_relation_work);
}

/**
 * yama_task_free - check for task_pid to remove from exception list
 * @task: task being removed
 */
void yama_task_free(struct task_struct *task)
{
	yama_ptracer_del(task, task);
}

/**
 * yama_task_prctl - check for Yama-specific prctl operations
 * @option: operation
 * @arg2: argument
 * @arg3: argument
 * @arg4: argument
 * @arg5: argument
 *
 * Return 0 on success, -ve on error.  -ENOSYS is returned when Yama
 * does not handle the given option.
 */
int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
			   unsigned long arg4, unsigned long arg5)
{
	int rc;
	struct task_struct *myself = current;

	rc = cap_task_prctl(option, arg2, arg3, arg4, arg5);
	if (rc != -ENOSYS)
		return rc;

	switch (option) {
	case PR_SET_PTRACER:
		/* Since a thread can call prctl(), find the group leader
		 * before calling _add() or _del() on it, since we want
		 * process-level granularity of control. The tracer group
		 * leader checking is handled later when walking the ancestry
		 * at the time of PTRACE_ATTACH check.
		 */
		rcu_read_lock();
		if (!thread_group_leader(myself))
			myself = rcu_dereference(myself->group_leader);
		get_task_struct(myself);
		rcu_read_unlock();

		if (arg2 == 0) {
			yama_ptracer_del(NULL, myself);
			rc = 0;
		} else if (arg2 == PR_SET_PTRACER_ANY || (int)arg2 == -1) {
			rc = yama_ptracer_add(NULL, myself);
		} else {
			struct task_struct *tracer;

			rcu_read_lock();
			tracer = find_task_by_vpid(arg2);
			if (tracer)
				get_task_struct(tracer);
			else
				rc = -EINVAL;
			rcu_read_unlock();

			if (tracer) {
				rc = yama_ptracer_add(tracer, myself);
				put_task_struct(tracer);
			}
		}

		put_task_struct(myself);
		break;
	}

	return rc;
}

/**
 * task_is_descendant - walk up a process family tree looking for a match
 * @parent: the process to compare against while walking up from child
 * @child: the process to start from while looking upwards for parent
 *
 * Returns 1 if child is a descendant of parent, 0 if not.
 */
static int task_is_descendant(struct task_struct *parent,
			      struct task_struct *child)
{
	int rc = 0;
	struct task_struct *walker = child;

	if (!parent || !child)
		return 0;

	rcu_read_lock();
	if (!thread_group_leader(parent))
		parent = rcu_dereference(parent->group_leader);
	while (walker->pid > 0) {
		if (!thread_group_leader(walker))
			walker = rcu_dereference(walker->group_leader);
		if (walker == parent) {
			rc = 1;
			break;
		}
		walker = rcu_dereference(walker->real_parent);
	}
	rcu_read_unlock();

	return rc;
}

/**
 * ptracer_exception_found - tracer registered as exception for this tracee
 * @tracer: the task_struct of the process attempting ptrace
 * @tracee: the task_struct of the process to be ptraced
 *
 * Returns 1 if tracer has is ptracer exception ancestor for tracee.
 */
static int ptracer_exception_found(struct task_struct *tracer,
				   struct task_struct *tracee)
{
	int rc = 0;
	struct ptrace_relation *relation;
	struct task_struct *parent = NULL;
	bool found = false;

	rcu_read_lock();
	if (!thread_group_leader(tracee))
		tracee = rcu_dereference(tracee->group_leader);
	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
		if (relation->invalid)
			continue;
		if (relation->tracee == tracee) {
			parent = relation->tracer;
			found = true;
			break;
		}
	}

	if (found && (parent == NULL || task_is_descendant(parent, tracer)))
		rc = 1;
	rcu_read_unlock();

	return rc;
}

/**
 * yama_ptrace_access_check - validate PTRACE_ATTACH calls
 * @child: task that current task is attempting to ptrace
 * @mode: ptrace attach mode
 *
 * Returns 0 if following the ptrace is allowed, -ve on error.
 */
int yama_ptrace_access_check(struct task_struct *child,
				    unsigned int mode)
{
	int rc;

	/* If standard caps disallows it, so does Yama.  We should
	 * only tighten restrictions further.
	 */
	rc = cap_ptrace_access_check(child, mode);
	if (rc)
		return rc;

	/* require ptrace target be a child of ptracer on attach */
	if (mode == PTRACE_MODE_ATTACH) {
		switch (ptrace_scope) {
		case YAMA_SCOPE_DISABLED:
			/* No additional restrictions. */
			break;
		case YAMA_SCOPE_RELATIONAL:
			if (!task_is_descendant(current, child) &&
			    !ptracer_exception_found(current, child) &&
			    !ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
				rc = -EPERM;
			break;
		case YAMA_SCOPE_CAPABILITY:
			if (!ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
				rc = -EPERM;
			break;
		case YAMA_SCOPE_NO_ATTACH:
		default:
			rc = -EPERM;
			break;
		}
	}

	if (rc) {
		printk_ratelimited(KERN_NOTICE
			"ptrace of pid %d was attempted by: %s (pid %d)\n",
			child->pid, current->comm, current->pid);
	}

	return rc;
}

/**
 * yama_ptrace_traceme - validate PTRACE_TRACEME calls
 * @parent: task that will become the ptracer of the current task
 *
 * Returns 0 if following the ptrace is allowed, -ve on error.
 */
int yama_ptrace_traceme(struct task_struct *parent)
{
	int rc;

	/* If standard caps disallows it, so does Yama.  We should
	 * only tighten restrictions further.
	 */
	rc = cap_ptrace_traceme(parent);
	if (rc)
		return rc;

	/* Only disallow PTRACE_TRACEME on more aggressive settings. */
	switch (ptrace_scope) {
	case YAMA_SCOPE_CAPABILITY:
		if (!ns_capable(task_user_ns(parent), CAP_SYS_PTRACE))
			rc = -EPERM;
		break;
	case YAMA_SCOPE_NO_ATTACH:
		rc = -EPERM;
		break;
	}

	if (rc) {
		printk_ratelimited(KERN_NOTICE
			"ptraceme of pid %d was attempted by: %s (pid %d)\n",
			current->pid, parent->comm, parent->pid);
	}

	return rc;
}

#ifndef CONFIG_SECURITY_YAMA_STACKED
static struct security_operations yama_ops = {
	.name =			"yama",

	.ptrace_access_check =	yama_ptrace_access_check,
	.ptrace_traceme =	yama_ptrace_traceme,
	.task_prctl =		yama_task_prctl,
	.task_free =		yama_task_free,
};
#endif

#ifdef CONFIG_SYSCTL
static int yama_dointvec_minmax(struct ctl_table *table, int write,
				void __user *buffer, size_t *lenp, loff_t *ppos)
{
	int rc;

	if (write && !capable(CAP_SYS_PTRACE))
		return -EPERM;

	rc = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
	if (rc)
		return rc;

	/* Lock the max value if it ever gets set. */
	if (write && *(int *)table->data == *(int *)table->extra2)
		table->extra1 = table->extra2;

	return rc;
}

static int zero;
static int max_scope = YAMA_SCOPE_NO_ATTACH;

struct ctl_path yama_sysctl_path[] = {
	{ .procname = "kernel", },
	{ .procname = "yama", },
	{ }
};

static struct ctl_table yama_sysctl_table[] = {
	{
		.procname       = "ptrace_scope",
		.data           = &ptrace_scope,
		.maxlen         = sizeof(int),
		.mode           = 0644,
		.proc_handler   = yama_dointvec_minmax,
		.extra1         = &zero,
		.extra2         = &max_scope,
	},
	{ }
};
#endif /* CONFIG_SYSCTL */

static __init int yama_init(void)
{
#ifndef CONFIG_SECURITY_YAMA_STACKED
	if (!security_module_enable(&yama_ops))
		return 0;
#endif

	printk(KERN_INFO "Yama: becoming mindful.\n");

#ifndef CONFIG_SECURITY_YAMA_STACKED
	if (register_security(&yama_ops))
		panic("Yama: kernel registration failed.\n");
#endif

#ifdef CONFIG_SYSCTL
	if (!register_sysctl_paths(yama_sysctl_path, yama_sysctl_table))
		panic("Yama: sysctl registration failed.\n");
#endif

	return 0;
}

security_initcall(yama_init);
Commit	Line	Data
2d514487 KC	1	/*
	2	* Yama Linux Security Module
	3	*
	4	* Author: Kees Cook <keescook@chromium.org>
	5	*
	6	* Copyright (C) 2010 Canonical, Ltd.
	7	* Copyright (C) 2011 The Chromium OS Authors.
	8	*
	9	* This program is free software; you can redistribute it and/or modify
	10	* it under the terms of the GNU General Public License version 2, as
	11	* published by the Free Software Foundation.
	12	*
	13	*/
	14
	15	#include <linux/security.h>
	16	#include <linux/sysctl.h>
	17	#include <linux/ptrace.h>
	18	#include <linux/prctl.h>
	19	#include <linux/ratelimit.h>
235e7527	20	#include <linux/workqueue.h>
2d514487	21
389da25f KC	22	#define YAMA_SCOPE_DISABLED 0
	23	#define YAMA_SCOPE_RELATIONAL 1
	24	#define YAMA_SCOPE_CAPABILITY 2
	25	#define YAMA_SCOPE_NO_ATTACH 3
	26
	27	static int ptrace_scope = YAMA_SCOPE_RELATIONAL;
2d514487 KC	28
	29	/* describe a ptrace relationship for potential exception */
	30	struct ptrace_relation {
	31	struct task_struct *tracer;
	32	struct task_struct *tracee;
235e7527	33	bool invalid;
2d514487	34	struct list_head node;
93b69d43	35	struct rcu_head rcu;
2d514487 KC	36	};
	37
	38	static LIST_HEAD(ptracer_relations);
	39	static DEFINE_SPINLOCK(ptracer_relations_lock);
	40
235e7527 KC	41	static void yama_relation_cleanup(struct work_struct *work);
	42	static DECLARE_WORK(yama_relation_work, yama_relation_cleanup);
	43
	44	/**
	45	* yama_relation_cleanup - remove invalid entries from the relation list
	46	*
	47	*/
	48	static void yama_relation_cleanup(struct work_struct *work)
	49	{
	50	struct ptrace_relation *relation;
	51
	52	spin_lock(&ptracer_relations_lock);
	53	rcu_read_lock();
	54	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
	55	if (relation->invalid) {
	56	list_del_rcu(&relation->node);
	57	kfree_rcu(relation, rcu);
	58	}
	59	}
	60	rcu_read_unlock();
	61	spin_unlock(&ptracer_relations_lock);
	62	}
	63
2d514487 KC	64	/**
	65	* yama_ptracer_add - add/replace an exception for this tracer/tracee pair
	66	* @tracer: the task_struct of the process doing the ptrace
	67	* @tracee: the task_struct of the process to be ptraced
	68	*
	69	* Each tracee can have, at most, one tracer registered. Each time this
	70	* is called, the prior registered tracer will be replaced for the tracee.
	71	*
	72	* Returns 0 if relationship was added, -ve on error.
	73	*/
	74	static int yama_ptracer_add(struct task_struct *tracer,
	75	struct task_struct *tracee)
	76	{
93b69d43	77	struct ptrace_relation relation, added;
2d514487 KC	78
	79	added = kmalloc(sizeof(*added), GFP_KERNEL);
	80	if (!added)
	81	return -ENOMEM;
	82
93b69d43 KC	83	added->tracee = tracee;
93b69d43 KC	84	added->tracer = tracer;
235e7527	85	added->invalid = false;
93b69d43	86
235e7527	87	spin_lock(&ptracer_relations_lock);
93b69d43 KC	88	rcu_read_lock();
93b69d43 KC	89	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
235e7527 KC	90	if (relation->invalid)
235e7527 KC	91	continue;
93b69d43 KC	92	if (relation->tracee == tracee) {
	93	list_replace_rcu(&relation->node, &added->node);
	94	kfree_rcu(relation, rcu);
	95	goto out;
2d514487	96	}
2d514487	97	}
2d514487	98
93b69d43	99	list_add_rcu(&added->node, &ptracer_relations);
2d514487	100
93b69d43 KC	101	out:
93b69d43 KC	102	rcu_read_unlock();
235e7527	103	spin_unlock(&ptracer_relations_lock);
93b69d43	104	return 0;
2d514487 KC	105	}
	106
	107	/**
	108	* yama_ptracer_del - remove exceptions related to the given tasks
	109	* @tracer: remove any relation where tracer task matches
	110	* @tracee: remove any relation where tracee task matches
	111	*/
	112	static void yama_ptracer_del(struct task_struct *tracer,
	113	struct task_struct *tracee)
	114	{
93b69d43	115	struct ptrace_relation *relation;
235e7527	116	bool marked = false;
2d514487	117
93b69d43 KC	118	rcu_read_lock();
93b69d43 KC	119	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
235e7527 KC	120	if (relation->invalid)
235e7527 KC	121	continue;
2d514487	122	if (relation->tracee == tracee \|\|
bf06189e	123	(tracer && relation->tracer == tracer)) {
235e7527 KC	124	relation->invalid = true;
235e7527 KC	125	marked = true;
2d514487	126	}
93b69d43 KC	127	}
93b69d43 KC	128	rcu_read_unlock();
235e7527 KC	129
	130	if (marked)
	131	schedule_work(&yama_relation_work);
2d514487 KC	132	}
	133
	134	/**
	135	* yama_task_free - check for task_pid to remove from exception list
	136	* @task: task being removed
	137	*/
c6993e4a	138	void yama_task_free(struct task_struct *task)
2d514487 KC	139	{
	140	yama_ptracer_del(task, task);
	141	}
	142
	143	/**
	144	* yama_task_prctl - check for Yama-specific prctl operations
	145	* @option: operation
	146	* @arg2: argument
	147	* @arg3: argument
	148	* @arg4: argument
	149	* @arg5: argument
	150	*
	151	* Return 0 on success, -ve on error. -ENOSYS is returned when Yama
	152	* does not handle the given option.
	153	*/
c6993e4a	154	int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
2d514487 KC	155	unsigned long arg4, unsigned long arg5)
	156	{
	157	int rc;
	158	struct task_struct *myself = current;
	159
	160	rc = cap_task_prctl(option, arg2, arg3, arg4, arg5);
	161	if (rc != -ENOSYS)
	162	return rc;
	163
	164	switch (option) {
	165	case PR_SET_PTRACER:
	166	/* Since a thread can call prctl(), find the group leader
	167	* before calling _add() or _del() on it, since we want
	168	* process-level granularity of control. The tracer group
	169	* leader checking is handled later when walking the ancestry
	170	* at the time of PTRACE_ATTACH check.
	171	*/
	172	rcu_read_lock();
	173	if (!thread_group_leader(myself))
	174	myself = rcu_dereference(myself->group_leader);
	175	get_task_struct(myself);
	176	rcu_read_unlock();
	177
	178	if (arg2 == 0) {
	179	yama_ptracer_del(NULL, myself);
	180	rc = 0;
2e4930eb	181	} else if (arg2 == PR_SET_PTRACER_ANY \|\| (int)arg2 == -1) {
bf06189e	182	rc = yama_ptracer_add(NULL, myself);
2d514487 KC	183	} else {
	184	struct task_struct *tracer;
	185
	186	rcu_read_lock();
	187	tracer = find_task_by_vpid(arg2);
	188	if (tracer)
	189	get_task_struct(tracer);
	190	else
	191	rc = -EINVAL;
	192	rcu_read_unlock();
	193
	194	if (tracer) {
	195	rc = yama_ptracer_add(tracer, myself);
	196	put_task_struct(tracer);
	197	}
	198	}
	199
	200	put_task_struct(myself);
	201	break;
	202	}
	203
	204	return rc;
	205	}
	206
	207	/**
	208	* task_is_descendant - walk up a process family tree looking for a match
	209	* @parent: the process to compare against while walking up from child
	210	* @child: the process to start from while looking upwards for parent
	211	*
	212	* Returns 1 if child is a descendant of parent, 0 if not.
	213	*/
	214	static int task_is_descendant(struct task_struct *parent,
	215	struct task_struct *child)
	216	{
	217	int rc = 0;
	218	struct task_struct *walker = child;
	219
	220	if (!parent \|\| !child)
	221	return 0;
	222
	223	rcu_read_lock();
	224	if (!thread_group_leader(parent))
	225	parent = rcu_dereference(parent->group_leader);
	226	while (walker->pid > 0) {
	227	if (!thread_group_leader(walker))
	228	walker = rcu_dereference(walker->group_leader);
	229	if (walker == parent) {
	230	rc = 1;
	231	break;
	232	}
	233	walker = rcu_dereference(walker->real_parent);
	234	}
	235	rcu_read_unlock();
	236
	237	return rc;
	238	}
	239
	240	/**
	241	* ptracer_exception_found - tracer registered as exception for this tracee
	242	* @tracer: the task_struct of the process attempting ptrace
	243	* @tracee: the task_struct of the process to be ptraced
	244	*
	245	* Returns 1 if tracer has is ptracer exception ancestor for tracee.
	246	*/
247	static int ptracer_exception_found(struct task_struct *tracer,
248	struct task_struct *tracee)
249	{
250	int rc = 0;
251	struct ptrace_relation *relation;
252	struct task_struct *parent = NULL;
bf06189e	253	bool found = false;
2d514487	254
2d514487 KC	255	rcu_read_lock();
	256	if (!thread_group_leader(tracee))
	257	tracee = rcu_dereference(tracee->group_leader);
235e7527 KC	258	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
	259	if (relation->invalid)
	260	continue;
2d514487 KC	261	if (relation->tracee == tracee) {
2d514487 KC	262	parent = relation->tracer;
bf06189e	263	found = true;
2d514487 KC	264	break;
2d514487 KC	265	}
235e7527	266	}
2d514487	267
bf06189e	268	if (found && (parent == NULL \|\| task_is_descendant(parent, tracer)))
2d514487 KC	269	rc = 1;
2d514487 KC	270	rcu_read_unlock();
2d514487 KC	271
	272	return rc;
	273	}
	274
	275	/**
	276	* yama_ptrace_access_check - validate PTRACE_ATTACH calls
	277	* @child: task that current task is attempting to ptrace
	278	* @mode: ptrace attach mode
	279	*
	280	* Returns 0 if following the ptrace is allowed, -ve on error.
	281	*/
c6993e4a	282	int yama_ptrace_access_check(struct task_struct *child,
2d514487 KC	283	unsigned int mode)
	284	{
	285	int rc;
	286
	287	/* If standard caps disallows it, so does Yama. We should
	288	* only tighten restrictions further.
	289	*/
	290	rc = cap_ptrace_access_check(child, mode);
	291	if (rc)
	292	return rc;
	293
	294	/* require ptrace target be a child of ptracer on attach */
389da25f KC	295	if (mode == PTRACE_MODE_ATTACH) {
	296	switch (ptrace_scope) {
	297	case YAMA_SCOPE_DISABLED:
	298	/* No additional restrictions. */
	299	break;
	300	case YAMA_SCOPE_RELATIONAL:
	301	if (!task_is_descendant(current, child) &&
	302	!ptracer_exception_found(current, child) &&
2cc8a716	303	!ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
389da25f KC	304	rc = -EPERM;
	305	break;
	306	case YAMA_SCOPE_CAPABILITY:
2cc8a716	307	if (!ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
389da25f KC	308	rc = -EPERM;
	309	break;
	310	case YAMA_SCOPE_NO_ATTACH:
	311	default:
	312	rc = -EPERM;
	313	break;
	314	}
	315	}
2d514487 KC	316
2d514487 KC	317	if (rc) {
389da25f KC	318	printk_ratelimited(KERN_NOTICE
389da25f KC	319	"ptrace of pid %d was attempted by: %s (pid %d)\n",
7612bfee	320	child->pid, current->comm, current->pid);
2d514487 KC	321	}
	322
	323	return rc;
	324	}
	325
9d8dad74 KC	326	/**
	327	* yama_ptrace_traceme - validate PTRACE_TRACEME calls
	328	* @parent: task that will become the ptracer of the current task
	329	*
	330	* Returns 0 if following the ptrace is allowed, -ve on error.
	331	*/
c6993e4a	332	int yama_ptrace_traceme(struct task_struct *parent)
9d8dad74 KC	333	{
	334	int rc;
	335
	336	/* If standard caps disallows it, so does Yama. We should
	337	* only tighten restrictions further.
	338	*/
	339	rc = cap_ptrace_traceme(parent);
	340	if (rc)
	341	return rc;
	342
	343	/* Only disallow PTRACE_TRACEME on more aggressive settings. */
	344	switch (ptrace_scope) {
	345	case YAMA_SCOPE_CAPABILITY:
	346	if (!ns_capable(task_user_ns(parent), CAP_SYS_PTRACE))
	347	rc = -EPERM;
	348	break;
	349	case YAMA_SCOPE_NO_ATTACH:
	350	rc = -EPERM;
	351	break;
	352	}
	353
	354	if (rc) {
9d8dad74 KC	355	printk_ratelimited(KERN_NOTICE
9d8dad74 KC	356	"ptraceme of pid %d was attempted by: %s (pid %d)\n",
7612bfee	357	current->pid, parent->comm, parent->pid);
9d8dad74 KC	358	}
	359
	360	return rc;
	361	}
	362
c6993e4a	363	#ifndef CONFIG_SECURITY_YAMA_STACKED
2d514487 KC	364	static struct security_operations yama_ops = {
	365	.name = "yama",
	366
	367	.ptrace_access_check = yama_ptrace_access_check,
9d8dad74	368	.ptrace_traceme = yama_ptrace_traceme,
2d514487 KC	369	.task_prctl = yama_task_prctl,
	370	.task_free = yama_task_free,
	371	};
c6993e4a	372	#endif
2d514487 KC	373
2d514487 KC	374	#ifdef CONFIG_SYSCTL
389da25f KC	375	static int yama_dointvec_minmax(struct ctl_table *table, int write,
	376	void __user buffer, size_t lenp, loff_t *ppos)
	377	{
	378	int rc;
	379
	380	if (write && !capable(CAP_SYS_PTRACE))
	381	return -EPERM;
	382
	383	rc = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
	384	if (rc)
	385	return rc;
	386
	387	/* Lock the max value if it ever gets set. */
	388	if (write && (int )table->data == (int )table->extra2)
	389	table->extra1 = table->extra2;
	390
	391	return rc;
	392	}
	393
2d514487	394	static int zero;
389da25f	395	static int max_scope = YAMA_SCOPE_NO_ATTACH;
2d514487 KC	396
	397	struct ctl_path yama_sysctl_path[] = {
	398	{ .procname = "kernel", },
	399	{ .procname = "yama", },
	400	{ }
	401	};
	402
	403	static struct ctl_table yama_sysctl_table[] = {
	404	{
	405	.procname = "ptrace_scope",
	406	.data = &ptrace_scope,
	407	.maxlen = sizeof(int),
	408	.mode = 0644,
389da25f	409	.proc_handler = yama_dointvec_minmax,
2d514487	410	.extra1 = &zero,
389da25f	411	.extra2 = &max_scope,
2d514487 KC	412	},
	413	{ }
	414	};
	415	#endif /* CONFIG_SYSCTL */
	416
	417	static __init int yama_init(void)
	418	{
c6993e4a	419	#ifndef CONFIG_SECURITY_YAMA_STACKED
2d514487 KC	420	if (!security_module_enable(&yama_ops))
2d514487 KC	421	return 0;
c6993e4a	422	#endif
2d514487 KC	423
	424	printk(KERN_INFO "Yama: becoming mindful.\n");
	425
c6993e4a	426	#ifndef CONFIG_SECURITY_YAMA_STACKED
2d514487 KC	427	if (register_security(&yama_ops))
2d514487 KC	428	panic("Yama: kernel registration failed.\n");
c6993e4a	429	#endif
2d514487 KC	430
	431	#ifdef CONFIG_SYSCTL
	432	if (!register_sysctl_paths(yama_sysctl_path, yama_sysctl_table))
	433	panic("Yama: sysctl registration failed.\n");
	434	#endif
	435
	436	return 0;
	437	}
	438
	439	security_initcall(yama_init);