[deliverable/linux.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>
#include <linux/string_helpers.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);

static void report_access(const char *access, struct task_struct *target,
			  struct task_struct *agent)
{
	char *target_cmd, *agent_cmd;

	target_cmd = kstrdup_quotable_cmdline(target, GFP_ATOMIC);
	agent_cmd = kstrdup_quotable_cmdline(agent, GFP_ATOMIC);

	pr_notice_ratelimited(
		"ptrace %s of \"%s\"[%d] was attempted by \"%s\"[%d]\n",
		access, target_cmd, target->pid, agent_cmd, agent->pid);

	kfree(agent_cmd);
	kfree(target_cmd);
}

/**
 * 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 && (mode & PTRACE_MODE_NOAUDIT) == 0)
		report_access("attach", child, current);

	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)
		report_access("traceme", current, parent);

	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),
};

#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,
	},
	{ }
};
static void __init yama_init_sysctl(void)
{
	if (!register_sysctl_paths(yama_sysctl_path, yama_sysctl_table))
		panic("Yama: sysctl registration failed.\n");
}
#else
static inline void yama_init_sysctl(void) { }
#endif /* CONFIG_SYSCTL */

void __init yama_add_hooks(void)
{
	pr_info("Yama: becoming mindful.\n");
	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks));
	yama_init_sysctl();
}
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>
8a56038c	21	#include <linux/string_helpers.h>
2d514487	22
389da25f KC	23	#define YAMA_SCOPE_DISABLED 0
	24	#define YAMA_SCOPE_RELATIONAL 1
	25	#define YAMA_SCOPE_CAPABILITY 2
	26	#define YAMA_SCOPE_NO_ATTACH 3
	27
	28	static int ptrace_scope = YAMA_SCOPE_RELATIONAL;
2d514487 KC	29
	30	/* describe a ptrace relationship for potential exception */
	31	struct ptrace_relation {
	32	struct task_struct *tracer;
	33	struct task_struct *tracee;
235e7527	34	bool invalid;
2d514487	35	struct list_head node;
93b69d43	36	struct rcu_head rcu;
2d514487 KC	37	};
	38
	39	static LIST_HEAD(ptracer_relations);
	40	static DEFINE_SPINLOCK(ptracer_relations_lock);
	41
235e7527 KC	42	static void yama_relation_cleanup(struct work_struct *work);
	43	static DECLARE_WORK(yama_relation_work, yama_relation_cleanup);
	44
8a56038c KC	45	static void report_access(const char access, struct task_struct target,
	46	struct task_struct *agent)
	47	{
	48	char target_cmd, agent_cmd;
	49
74f430cd SL	50	target_cmd = kstrdup_quotable_cmdline(target, GFP_ATOMIC);
74f430cd SL	51	agent_cmd = kstrdup_quotable_cmdline(agent, GFP_ATOMIC);
8a56038c KC	52
	53	pr_notice_ratelimited(
	54	"ptrace %s of \"%s\"[%d] was attempted by \"%s\"[%d]\n",
	55	access, target_cmd, target->pid, agent_cmd, agent->pid);
	56
	57	kfree(agent_cmd);
	58	kfree(target_cmd);
	59	}
	60
235e7527 KC	61	/**
	62	* yama_relation_cleanup - remove invalid entries from the relation list
	63	*
	64	*/
	65	static void yama_relation_cleanup(struct work_struct *work)
	66	{
	67	struct ptrace_relation *relation;
	68
	69	spin_lock(&ptracer_relations_lock);
	70	rcu_read_lock();
	71	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
	72	if (relation->invalid) {
	73	list_del_rcu(&relation->node);
	74	kfree_rcu(relation, rcu);
	75	}
	76	}
	77	rcu_read_unlock();
	78	spin_unlock(&ptracer_relations_lock);
	79	}
	80
2d514487 KC	81	/**
	82	* yama_ptracer_add - add/replace an exception for this tracer/tracee pair
	83	* @tracer: the task_struct of the process doing the ptrace
	84	* @tracee: the task_struct of the process to be ptraced
	85	*
	86	* Each tracee can have, at most, one tracer registered. Each time this
	87	* is called, the prior registered tracer will be replaced for the tracee.
	88	*
	89	* Returns 0 if relationship was added, -ve on error.
	90	*/
	91	static int yama_ptracer_add(struct task_struct *tracer,
	92	struct task_struct *tracee)
	93	{
93b69d43	94	struct ptrace_relation relation, added;
2d514487 KC	95
	96	added = kmalloc(sizeof(*added), GFP_KERNEL);
	97	if (!added)
	98	return -ENOMEM;
	99
93b69d43 KC	100	added->tracee = tracee;
93b69d43 KC	101	added->tracer = tracer;
235e7527	102	added->invalid = false;
93b69d43	103
235e7527	104	spin_lock(&ptracer_relations_lock);
93b69d43 KC	105	rcu_read_lock();
93b69d43 KC	106	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
235e7527 KC	107	if (relation->invalid)
235e7527 KC	108	continue;
93b69d43 KC	109	if (relation->tracee == tracee) {
	110	list_replace_rcu(&relation->node, &added->node);
	111	kfree_rcu(relation, rcu);
	112	goto out;
2d514487	113	}
2d514487	114	}
2d514487	115
93b69d43	116	list_add_rcu(&added->node, &ptracer_relations);
2d514487	117
93b69d43 KC	118	out:
93b69d43 KC	119	rcu_read_unlock();
235e7527	120	spin_unlock(&ptracer_relations_lock);
93b69d43	121	return 0;
2d514487 KC	122	}
	123
	124	/**
	125	* yama_ptracer_del - remove exceptions related to the given tasks
	126	* @tracer: remove any relation where tracer task matches
	127	* @tracee: remove any relation where tracee task matches
	128	*/
	129	static void yama_ptracer_del(struct task_struct *tracer,
	130	struct task_struct *tracee)
	131	{
93b69d43	132	struct ptrace_relation *relation;
235e7527	133	bool marked = false;
2d514487	134
93b69d43 KC	135	rcu_read_lock();
93b69d43 KC	136	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
235e7527 KC	137	if (relation->invalid)
235e7527 KC	138	continue;
2d514487	139	if (relation->tracee == tracee \|\|
bf06189e	140	(tracer && relation->tracer == tracer)) {
235e7527 KC	141	relation->invalid = true;
235e7527 KC	142	marked = true;
2d514487	143	}
93b69d43 KC	144	}
93b69d43 KC	145	rcu_read_unlock();
235e7527 KC	146
	147	if (marked)
	148	schedule_work(&yama_relation_work);
2d514487 KC	149	}
	150
	151	/**
	152	* yama_task_free - check for task_pid to remove from exception list
	153	* @task: task being removed
	154	*/
c6993e4a	155	void yama_task_free(struct task_struct *task)
2d514487 KC	156	{
	157	yama_ptracer_del(task, task);
	158	}
	159
	160	/**
	161	* yama_task_prctl - check for Yama-specific prctl operations
	162	* @option: operation
	163	* @arg2: argument
	164	* @arg3: argument
	165	* @arg4: argument
	166	* @arg5: argument
	167	*
	168	* Return 0 on success, -ve on error. -ENOSYS is returned when Yama
	169	* does not handle the given option.
	170	*/
c6993e4a	171	int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
2d514487 KC	172	unsigned long arg4, unsigned long arg5)
2d514487 KC	173	{
b1d9e6b0	174	int rc = -ENOSYS;
2d514487 KC	175	struct task_struct *myself = current;
2d514487 KC	176
2d514487 KC	177	switch (option) {
	178	case PR_SET_PTRACER:
	179	/* Since a thread can call prctl(), find the group leader
	180	* before calling _add() or _del() on it, since we want
	181	* process-level granularity of control. The tracer group
	182	* leader checking is handled later when walking the ancestry
	183	* at the time of PTRACE_ATTACH check.
	184	*/
	185	rcu_read_lock();
	186	if (!thread_group_leader(myself))
	187	myself = rcu_dereference(myself->group_leader);
	188	get_task_struct(myself);
	189	rcu_read_unlock();
	190
	191	if (arg2 == 0) {
	192	yama_ptracer_del(NULL, myself);
	193	rc = 0;
2e4930eb	194	} else if (arg2 == PR_SET_PTRACER_ANY \|\| (int)arg2 == -1) {
bf06189e	195	rc = yama_ptracer_add(NULL, myself);
2d514487 KC	196	} else {
	197	struct task_struct *tracer;
	198
	199	rcu_read_lock();
	200	tracer = find_task_by_vpid(arg2);
	201	if (tracer)
	202	get_task_struct(tracer);
	203	else
	204	rc = -EINVAL;
	205	rcu_read_unlock();
	206
	207	if (tracer) {
	208	rc = yama_ptracer_add(tracer, myself);
	209	put_task_struct(tracer);
	210	}
	211	}
	212
	213	put_task_struct(myself);
	214	break;
	215	}
	216
	217	return rc;
	218	}
	219
	220	/**
	221	* task_is_descendant - walk up a process family tree looking for a match
	222	* @parent: the process to compare against while walking up from child
	223	* @child: the process to start from while looking upwards for parent
	224	*
	225	* Returns 1 if child is a descendant of parent, 0 if not.
	226	*/
	227	static int task_is_descendant(struct task_struct *parent,
	228	struct task_struct *child)
	229	{
	230	int rc = 0;
	231	struct task_struct *walker = child;
	232
	233	if (!parent \|\| !child)
	234	return 0;
	235
	236	rcu_read_lock();
	237	if (!thread_group_leader(parent))
	238	parent = rcu_dereference(parent->group_leader);
	239	while (walker->pid > 0) {
	240	if (!thread_group_leader(walker))
	241	walker = rcu_dereference(walker->group_leader);
	242	if (walker == parent) {
	243	rc = 1;
	244	break;
	245	}
	246	walker = rcu_dereference(walker->real_parent);
	247	}
	248	rcu_read_unlock();
	249
	250	return rc;
	251	}
	252
	253	/**
	254	* ptracer_exception_found - tracer registered as exception for this tracee
	255	* @tracer: the task_struct of the process attempting ptrace
	256	* @tracee: the task_struct of the process to be ptraced
	257	*
	258	* Returns 1 if tracer has is ptracer exception ancestor for tracee.
	259	*/
260	static int ptracer_exception_found(struct task_struct *tracer,
261	struct task_struct *tracee)
262	{
263	int rc = 0;
264	struct ptrace_relation *relation;
265	struct task_struct *parent = NULL;
bf06189e	266	bool found = false;
2d514487	267
2d514487 KC	268	rcu_read_lock();
	269	if (!thread_group_leader(tracee))
	270	tracee = rcu_dereference(tracee->group_leader);
235e7527 KC	271	list_for_each_entry_rcu(relation, &ptracer_relations, node) {
	272	if (relation->invalid)
	273	continue;
2d514487 KC	274	if (relation->tracee == tracee) {
2d514487 KC	275	parent = relation->tracer;
bf06189e	276	found = true;
2d514487 KC	277	break;
2d514487 KC	278	}
235e7527	279	}
2d514487	280
bf06189e	281	if (found && (parent == NULL \|\| task_is_descendant(parent, tracer)))
2d514487 KC	282	rc = 1;
2d514487 KC	283	rcu_read_unlock();
2d514487 KC	284
	285	return rc;
	286	}
	287
	288	/**
	289	* yama_ptrace_access_check - validate PTRACE_ATTACH calls
	290	* @child: task that current task is attempting to ptrace
	291	* @mode: ptrace attach mode
	292	*
	293	* Returns 0 if following the ptrace is allowed, -ve on error.
	294	*/
b1d9e6b0	295	static int yama_ptrace_access_check(struct task_struct *child,
2d514487 KC	296	unsigned int mode)
2d514487 KC	297	{
b1d9e6b0	298	int rc = 0;
2d514487 KC	299
2d514487 KC	300	/* require ptrace target be a child of ptracer on attach */
3dfb7d8c	301	if (mode & PTRACE_MODE_ATTACH) {
389da25f KC	302	switch (ptrace_scope) {
	303	case YAMA_SCOPE_DISABLED:
	304	/* No additional restrictions. */
	305	break;
	306	case YAMA_SCOPE_RELATIONAL:
4c44aaaf	307	rcu_read_lock();
389da25f KC	308	if (!task_is_descendant(current, child) &&
389da25f KC	309	!ptracer_exception_found(current, child) &&
4c44aaaf	310	!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
389da25f	311	rc = -EPERM;
4c44aaaf	312	rcu_read_unlock();
389da25f KC	313	break;
389da25f KC	314	case YAMA_SCOPE_CAPABILITY:
4c44aaaf EB	315	rcu_read_lock();
4c44aaaf EB	316	if (!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
389da25f	317	rc = -EPERM;
4c44aaaf	318	rcu_read_unlock();
389da25f KC	319	break;
	320	case YAMA_SCOPE_NO_ATTACH:
	321	default:
	322	rc = -EPERM;
	323	break;
	324	}
	325	}
2d514487	326
8a56038c KC	327	if (rc && (mode & PTRACE_MODE_NOAUDIT) == 0)
8a56038c KC	328	report_access("attach", child, current);
2d514487 KC	329
	330	return rc;
	331	}
	332
9d8dad74 KC	333	/**
	334	* yama_ptrace_traceme - validate PTRACE_TRACEME calls
	335	* @parent: task that will become the ptracer of the current task
	336	*
	337	* Returns 0 if following the ptrace is allowed, -ve on error.
	338	*/
c6993e4a	339	int yama_ptrace_traceme(struct task_struct *parent)
9d8dad74	340	{
b1d9e6b0	341	int rc = 0;
9d8dad74 KC	342
	343	/* Only disallow PTRACE_TRACEME on more aggressive settings. */
	344	switch (ptrace_scope) {
	345	case YAMA_SCOPE_CAPABILITY:
eddc0a3a	346	if (!has_ns_capability(parent, current_user_ns(), CAP_SYS_PTRACE))
9d8dad74 KC	347	rc = -EPERM;
	348	break;
	349	case YAMA_SCOPE_NO_ATTACH:
	350	rc = -EPERM;
	351	break;
	352	}
	353
8a56038c KC	354	if (rc)
8a56038c KC	355	report_access("traceme", current, parent);
9d8dad74 KC	356
	357	return rc;
	358	}
	359
b1d9e6b0	360	static struct security_hook_list yama_hooks[] = {
e20b043a CS	361	LSM_HOOK_INIT(ptrace_access_check, yama_ptrace_access_check),
	362	LSM_HOOK_INIT(ptrace_traceme, yama_ptrace_traceme),
	363	LSM_HOOK_INIT(task_prctl, yama_task_prctl),
	364	LSM_HOOK_INIT(task_free, yama_task_free),
2d514487	365	};
b1d9e6b0	366
2d514487	367	#ifdef CONFIG_SYSCTL
389da25f KC	368	static int yama_dointvec_minmax(struct ctl_table *table, int write,
	369	void __user buffer, size_t lenp, loff_t *ppos)
	370	{
41a4695c	371	struct ctl_table table_copy;
389da25f KC	372
	373	if (write && !capable(CAP_SYS_PTRACE))
	374	return -EPERM;
	375
389da25f	376	/* Lock the max value if it ever gets set. */
41a4695c KC	377	table_copy = *table;
	378	if ((int )table_copy.data == (int )table_copy.extra2)
	379	table_copy.extra1 = table_copy.extra2;
389da25f	380
41a4695c	381	return proc_dointvec_minmax(&table_copy, write, buffer, lenp, ppos);
389da25f KC	382	}
389da25f KC	383
2d514487	384	static int zero;
389da25f	385	static int max_scope = YAMA_SCOPE_NO_ATTACH;
2d514487 KC	386
	387	struct ctl_path yama_sysctl_path[] = {
	388	{ .procname = "kernel", },
	389	{ .procname = "yama", },
	390	{ }
	391	};
	392
	393	static struct ctl_table yama_sysctl_table[] = {
	394	{
	395	.procname = "ptrace_scope",
	396	.data = &ptrace_scope,
	397	.maxlen = sizeof(int),
	398	.mode = 0644,
389da25f	399	.proc_handler = yama_dointvec_minmax,
2d514487	400	.extra1 = &zero,
389da25f	401	.extra2 = &max_scope,
2d514487 KC	402	},
	403	{ }
	404	};
730daa16	405	static void __init yama_init_sysctl(void)
2d514487	406	{
2d514487 KC	407	if (!register_sysctl_paths(yama_sysctl_path, yama_sysctl_table))
2d514487 KC	408	panic("Yama: sysctl registration failed.\n");
2d514487	409	}
730daa16 KC	410	#else
	411	static inline void yama_init_sysctl(void) { }
	412	#endif /* CONFIG_SYSCTL */
2d514487	413
730daa16 KC	414	void __init yama_add_hooks(void)
	415	{
	416	pr_info("Yama: becoming mindful.\n");
	417	security_add_hooks(yama_hooks, ARRAY_SIZE(yama_hooks));
	418	yama_init_sysctl();
	419	}