[linux-2.6-block.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/lsm_hooks.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 = -ENOSYS;
	struct task_struct *myself = current;

	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.
 */
static int yama_ptrace_access_check(struct task_struct *child,
				    unsigned int mode)
{
	int rc = 0;

	/* 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:
			rcu_read_lock();
			if (!task_is_descendant(current, child) &&
			    !ptracer_exception_found(current, child) &&
			    !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
				rc = -EPERM;
			rcu_read_unlock();
			break;
		case YAMA_SCOPE_CAPABILITY:
			rcu_read_lock();
			if (!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
				rc = -EPERM;
			rcu_read_unlock();
			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 = 0;

	/* Only disallow PTRACE_TRACEME on more aggressive settings. */
	switch (ptrace_scope) {
	case YAMA_SCOPE_CAPABILITY:
		if (!has_ns_capability(parent, current_user_ns(), 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;
}

static struct security_hook_list yama_hooks[] = {
	LSM_HOOK_INIT(ptrace_access_check, yama_ptrace_access_check),
	LSM_HOOK_INIT(ptrace_traceme, yama_ptrace_traceme),
	LSM_HOOK_INIT(task_prctl, yama_task_prctl),
	LSM_HOOK_INIT(task_free, yama_task_free),
};

void __init yama_add_hooks(void)
{
	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks));
}

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

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

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

	return proc_dointvec_minmax(&table_copy, write, buffer, lenp, ppos);
}

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 yama is being stacked this is already taken care of.
	 */
	if (!security_module_enable("yama"))
		return 0;
#endif
	pr_info("Yama: becoming mindful.\n");

#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
3c4ed7bd	15	#include <linux/lsm_hooks.h>
2d514487 KC	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)
2d514487 KC	156	{
b1d9e6b0	157	int rc = -ENOSYS;
2d514487 KC	158	struct task_struct *myself = current;
2d514487 KC	159
2d514487 KC	160	switch (option) {
	161	case PR_SET_PTRACER:
	162	/* Since a thread can call prctl(), find the group leader
	163	* before calling _add() or _del() on it, since we want
	164	* process-level granularity of control. The tracer group
	165	* leader checking is handled later when walking the ancestry
	166	* at the time of PTRACE_ATTACH check.
	167	*/
	168	rcu_read_lock();
	169	if (!thread_group_leader(myself))
	170	myself = rcu_dereference(myself->group_leader);
	171	get_task_struct(myself);
	172	rcu_read_unlock();
	173
	174	if (arg2 == 0) {
	175	yama_ptracer_del(NULL, myself);
	176	rc = 0;
2e4930eb	177	} else if (arg2 == PR_SET_PTRACER_ANY \|\| (int)arg2 == -1) {
bf06189e	178	rc = yama_ptracer_add(NULL, myself);
2d514487 KC	179	} else {
	180	struct task_struct *tracer;
	181
	182	rcu_read_lock();
	183	tracer = find_task_by_vpid(arg2);
	184	if (tracer)
	185	get_task_struct(tracer);
	186	else
	187	rc = -EINVAL;
	188	rcu_read_unlock();
	189
	190	if (tracer) {
	191	rc = yama_ptracer_add(tracer, myself);
	192	put_task_struct(tracer);
	193	}
	194	}
	195
	196	put_task_struct(myself);
	197	break;
	198	}
	199
	200	return rc;
	201	}
	202
	203	/**
	204	* task_is_descendant - walk up a process family tree looking for a match
	205	* @parent: the process to compare against while walking up from child
	206	* @child: the process to start from while looking upwards for parent
	207	*
	208	* Returns 1 if child is a descendant of parent, 0 if not.
	209	*/
	210	static int task_is_descendant(struct task_struct *parent,
	211	struct task_struct *child)
	212	{
	213	int rc = 0;
	214	struct task_struct *walker = child;
	215
	216	if (!parent \|\| !child)
	217	return 0;
	218
	219	rcu_read_lock();
	220	if (!thread_group_leader(parent))
	221	parent = rcu_dereference(parent->group_leader);
	222	while (walker->pid > 0) {
	223	if (!thread_group_leader(walker))
	224	walker = rcu_dereference(walker->group_leader);
	225	if (walker == parent) {
	226	rc = 1;
	227	break;
	228	}
	229	walker = rcu_dereference(walker->real_parent);
	230	}
	231	rcu_read_unlock();
	232
	233	return rc;
	234	}
	235
	236	/**
	237	* ptracer_exception_found - tracer registered as exception for this tracee
	238	* @tracer: the task_struct of the process attempting ptrace
	239	* @tracee: the task_struct of the process to be ptraced
	240	*
	241	* Returns 1 if tracer has is ptracer exception ancestor for tracee.
	242	*/
243	static int ptracer_exception_found(struct task_struct *tracer,
244	struct task_struct *tracee)
245	{
246	int rc = 0;
247	struct ptrace_relation *relation;
248	struct task_struct *parent = NULL;
bf06189e	249	bool found = false;
2d514487	250
2d514487 KC	251	rcu_read_lock();
	252	if (!thread_group_leader(tracee))
	253	tracee = rcu_dereference(tracee->group_leader);
235e7527 KC	254	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
	255	if (relation->invalid)
	256	continue;
2d514487 KC	257	if (relation->tracee == tracee) {
2d514487 KC	258	parent = relation->tracer;
bf06189e	259	found = true;
2d514487 KC	260	break;
2d514487 KC	261	}
235e7527	262	}
2d514487	263
bf06189e	264	if (found && (parent == NULL \|\| task_is_descendant(parent, tracer)))
2d514487 KC	265	rc = 1;
2d514487 KC	266	rcu_read_unlock();
2d514487 KC	267
	268	return rc;
	269	}
	270
	271	/**
	272	* yama_ptrace_access_check - validate PTRACE_ATTACH calls
	273	* @child: task that current task is attempting to ptrace
	274	* @mode: ptrace attach mode
	275	*
	276	* Returns 0 if following the ptrace is allowed, -ve on error.
	277	*/
b1d9e6b0	278	static int yama_ptrace_access_check(struct task_struct *child,
2d514487 KC	279	unsigned int mode)
2d514487 KC	280	{
b1d9e6b0	281	int rc = 0;
2d514487 KC	282
2d514487 KC	283	/* require ptrace target be a child of ptracer on attach */
389da25f KC	284	if (mode == PTRACE_MODE_ATTACH) {
	285	switch (ptrace_scope) {
	286	case YAMA_SCOPE_DISABLED:
	287	/* No additional restrictions. */
	288	break;
	289	case YAMA_SCOPE_RELATIONAL:
4c44aaaf	290	rcu_read_lock();
389da25f KC	291	if (!task_is_descendant(current, child) &&
389da25f KC	292	!ptracer_exception_found(current, child) &&
4c44aaaf	293	!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
389da25f	294	rc = -EPERM;
4c44aaaf	295	rcu_read_unlock();
389da25f KC	296	break;
389da25f KC	297	case YAMA_SCOPE_CAPABILITY:
4c44aaaf EB	298	rcu_read_lock();
4c44aaaf EB	299	if (!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
389da25f	300	rc = -EPERM;
4c44aaaf	301	rcu_read_unlock();
389da25f KC	302	break;
	303	case YAMA_SCOPE_NO_ATTACH:
	304	default:
	305	rc = -EPERM;
	306	break;
	307	}
	308	}
2d514487 KC	309
2d514487 KC	310	if (rc) {
389da25f KC	311	printk_ratelimited(KERN_NOTICE
389da25f KC	312	"ptrace of pid %d was attempted by: %s (pid %d)\n",
7612bfee	313	child->pid, current->comm, current->pid);
2d514487 KC	314	}
	315
	316	return rc;
	317	}
	318
9d8dad74 KC	319	/**
	320	* yama_ptrace_traceme - validate PTRACE_TRACEME calls
	321	* @parent: task that will become the ptracer of the current task
	322	*
	323	* Returns 0 if following the ptrace is allowed, -ve on error.
	324	*/
c6993e4a	325	int yama_ptrace_traceme(struct task_struct *parent)
9d8dad74	326	{
b1d9e6b0	327	int rc = 0;
9d8dad74 KC	328
	329	/* Only disallow PTRACE_TRACEME on more aggressive settings. */
	330	switch (ptrace_scope) {
	331	case YAMA_SCOPE_CAPABILITY:
eddc0a3a	332	if (!has_ns_capability(parent, current_user_ns(), CAP_SYS_PTRACE))
9d8dad74 KC	333	rc = -EPERM;
	334	break;
	335	case YAMA_SCOPE_NO_ATTACH:
	336	rc = -EPERM;
	337	break;
	338	}
	339
	340	if (rc) {
9d8dad74 KC	341	printk_ratelimited(KERN_NOTICE
9d8dad74 KC	342	"ptraceme of pid %d was attempted by: %s (pid %d)\n",
7612bfee	343	current->pid, parent->comm, parent->pid);
9d8dad74 KC	344	}
	345
	346	return rc;
	347	}
	348
b1d9e6b0	349	static struct security_hook_list yama_hooks[] = {
e20b043a CS	350	LSM_HOOK_INIT(ptrace_access_check, yama_ptrace_access_check),
	351	LSM_HOOK_INIT(ptrace_traceme, yama_ptrace_traceme),
	352	LSM_HOOK_INIT(task_prctl, yama_task_prctl),
	353	LSM_HOOK_INIT(task_free, yama_task_free),
2d514487	354	};
b1d9e6b0 CS	355
	356	void __init yama_add_hooks(void)
	357	{
	358	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks));
	359	}
2d514487 KC	360
2d514487 KC	361	#ifdef CONFIG_SYSCTL
389da25f KC	362	static int yama_dointvec_minmax(struct ctl_table *table, int write,
	363	void __user buffer, size_t lenp, loff_t *ppos)
	364	{
41a4695c	365	struct ctl_table table_copy;
389da25f KC	366
	367	if (write && !capable(CAP_SYS_PTRACE))
	368	return -EPERM;
	369
389da25f	370	/* Lock the max value if it ever gets set. */
41a4695c KC	371	table_copy = *table;
	372	if ((int )table_copy.data == (int )table_copy.extra2)
	373	table_copy.extra1 = table_copy.extra2;
389da25f	374
41a4695c	375	return proc_dointvec_minmax(&table_copy, write, buffer, lenp, ppos);
389da25f KC	376	}
389da25f KC	377
2d514487	378	static int zero;
389da25f	379	static int max_scope = YAMA_SCOPE_NO_ATTACH;
2d514487 KC	380
	381	struct ctl_path yama_sysctl_path[] = {
	382	{ .procname = "kernel", },
	383	{ .procname = "yama", },
	384	{ }
	385	};
	386
	387	static struct ctl_table yama_sysctl_table[] = {
	388	{
	389	.procname = "ptrace_scope",
	390	.data = &ptrace_scope,
	391	.maxlen = sizeof(int),
	392	.mode = 0644,
389da25f	393	.proc_handler = yama_dointvec_minmax,
2d514487	394	.extra1 = &zero,
389da25f	395	.extra2 = &max_scope,
2d514487 KC	396	},
	397	{ }
	398	};
	399	#endif /* CONFIG_SYSCTL */
	400
	401	static __init int yama_init(void)
	402	{
c6993e4a	403	#ifndef CONFIG_SECURITY_YAMA_STACKED
b1d9e6b0 CS	404	/*
	405	* If yama is being stacked this is already taken care of.
	406	*/
	407	if (!security_module_enable("yama"))
2d514487	408	return 0;
c6993e4a	409	#endif
b1d9e6b0	410	pr_info("Yama: becoming mindful.\n");
2d514487 KC	411
	412	#ifdef CONFIG_SYSCTL
	413	if (!register_sysctl_paths(yama_sysctl_path, yama_sysctl_table))
	414	panic("Yama: sysctl registration failed.\n");
	415	#endif
	416
	417	return 0;
	418	}
	419
	420	security_initcall(yama_init);