2011-12-21 13:17:04 -07:00
|
|
|
/*
|
|
|
|
* 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>
|
2012-11-19 16:21:26 -07:00
|
|
|
#include <linux/workqueue.h>
|
2011-12-21 13:17:04 -07:00
|
|
|
|
2012-04-16 12:56:45 -06:00
|
|
|
#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;
|
2011-12-21 13:17:04 -07:00
|
|
|
|
|
|
|
/* describe a ptrace relationship for potential exception */
|
|
|
|
struct ptrace_relation {
|
|
|
|
struct task_struct *tracer;
|
|
|
|
struct task_struct *tracee;
|
2012-11-19 16:21:26 -07:00
|
|
|
bool invalid;
|
2011-12-21 13:17:04 -07:00
|
|
|
struct list_head node;
|
2012-10-18 15:53:58 -06:00
|
|
|
struct rcu_head rcu;
|
2011-12-21 13:17:04 -07:00
|
|
|
};
|
|
|
|
|
|
|
|
static LIST_HEAD(ptracer_relations);
|
|
|
|
static DEFINE_SPINLOCK(ptracer_relations_lock);
|
|
|
|
|
2012-11-19 16:21:26 -07:00
|
|
|
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);
|
|
|
|
}
|
|
|
|
|
2011-12-21 13:17:04 -07:00
|
|
|
/**
|
|
|
|
* 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)
|
|
|
|
{
|
2012-10-18 15:53:58 -06:00
|
|
|
struct ptrace_relation *relation, *added;
|
2011-12-21 13:17:04 -07:00
|
|
|
|
|
|
|
added = kmalloc(sizeof(*added), GFP_KERNEL);
|
|
|
|
if (!added)
|
|
|
|
return -ENOMEM;
|
|
|
|
|
2012-10-18 15:53:58 -06:00
|
|
|
added->tracee = tracee;
|
|
|
|
added->tracer = tracer;
|
2012-11-19 16:21:26 -07:00
|
|
|
added->invalid = false;
|
2012-10-18 15:53:58 -06:00
|
|
|
|
2012-11-19 16:21:26 -07:00
|
|
|
spin_lock(&ptracer_relations_lock);
|
2012-10-18 15:53:58 -06:00
|
|
|
rcu_read_lock();
|
|
|
|
list_for_each_entry_rcu(relation, &ptracer_relations, node) {
|
2012-11-19 16:21:26 -07:00
|
|
|
if (relation->invalid)
|
|
|
|
continue;
|
2012-10-18 15:53:58 -06:00
|
|
|
if (relation->tracee == tracee) {
|
|
|
|
list_replace_rcu(&relation->node, &added->node);
|
|
|
|
kfree_rcu(relation, rcu);
|
|
|
|
goto out;
|
2011-12-21 13:17:04 -07:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2012-10-18 15:53:58 -06:00
|
|
|
list_add_rcu(&added->node, &ptracer_relations);
|
2011-12-21 13:17:04 -07:00
|
|
|
|
2012-10-18 15:53:58 -06:00
|
|
|
out:
|
|
|
|
rcu_read_unlock();
|
2012-11-19 16:21:26 -07:00
|
|
|
spin_unlock(&ptracer_relations_lock);
|
2012-10-18 15:53:58 -06:00
|
|
|
return 0;
|
2011-12-21 13:17:04 -07:00
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* 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)
|
|
|
|
{
|
2012-10-18 15:53:58 -06:00
|
|
|
struct ptrace_relation *relation;
|
2012-11-19 16:21:26 -07:00
|
|
|
bool marked = false;
|
2011-12-21 13:17:04 -07:00
|
|
|
|
2012-10-18 15:53:58 -06:00
|
|
|
rcu_read_lock();
|
|
|
|
list_for_each_entry_rcu(relation, &ptracer_relations, node) {
|
2012-11-19 16:21:26 -07:00
|
|
|
if (relation->invalid)
|
|
|
|
continue;
|
2011-12-21 13:17:04 -07:00
|
|
|
if (relation->tracee == tracee ||
|
2012-02-14 17:48:09 -07:00
|
|
|
(tracer && relation->tracer == tracer)) {
|
2012-11-19 16:21:26 -07:00
|
|
|
relation->invalid = true;
|
|
|
|
marked = true;
|
2011-12-21 13:17:04 -07:00
|
|
|
}
|
2012-10-18 15:53:58 -06:00
|
|
|
}
|
|
|
|
rcu_read_unlock();
|
2012-11-19 16:21:26 -07:00
|
|
|
|
|
|
|
if (marked)
|
|
|
|
schedule_work(&yama_relation_work);
|
2011-12-21 13:17:04 -07:00
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* yama_task_free - check for task_pid to remove from exception list
|
|
|
|
* @task: task being removed
|
|
|
|
*/
|
2012-09-04 14:32:13 -06:00
|
|
|
void yama_task_free(struct task_struct *task)
|
2011-12-21 13:17:04 -07:00
|
|
|
{
|
|
|
|
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.
|
|
|
|
*/
|
2012-09-04 14:32:13 -06:00
|
|
|
int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
|
2011-12-21 13:17:04 -07:00
|
|
|
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;
|
2012-08-27 12:38:13 -06:00
|
|
|
} else if (arg2 == PR_SET_PTRACER_ANY || (int)arg2 == -1) {
|
2012-02-14 17:48:09 -07:00
|
|
|
rc = yama_ptracer_add(NULL, myself);
|
2011-12-21 13:17:04 -07:00
|
|
|
} 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;
|
2012-02-14 17:48:09 -07:00
|
|
|
bool found = false;
|
2011-12-21 13:17:04 -07:00
|
|
|
|
|
|
|
rcu_read_lock();
|
|
|
|
if (!thread_group_leader(tracee))
|
|
|
|
tracee = rcu_dereference(tracee->group_leader);
|
2012-11-19 16:21:26 -07:00
|
|
|
list_for_each_entry_rcu(relation, &ptracer_relations, node) {
|
|
|
|
if (relation->invalid)
|
|
|
|
continue;
|
2011-12-21 13:17:04 -07:00
|
|
|
if (relation->tracee == tracee) {
|
|
|
|
parent = relation->tracer;
|
2012-02-14 17:48:09 -07:00
|
|
|
found = true;
|
2011-12-21 13:17:04 -07:00
|
|
|
break;
|
|
|
|
}
|
2012-11-19 16:21:26 -07:00
|
|
|
}
|
2011-12-21 13:17:04 -07:00
|
|
|
|
2012-02-14 17:48:09 -07:00
|
|
|
if (found && (parent == NULL || task_is_descendant(parent, tracer)))
|
2011-12-21 13:17:04 -07:00
|
|
|
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.
|
|
|
|
*/
|
2012-09-04 14:32:13 -06:00
|
|
|
int yama_ptrace_access_check(struct task_struct *child,
|
2011-12-21 13:17:04 -07:00
|
|
|
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 */
|
2012-04-16 12:56:45 -06:00
|
|
|
if (mode == PTRACE_MODE_ATTACH) {
|
|
|
|
switch (ptrace_scope) {
|
|
|
|
case YAMA_SCOPE_DISABLED:
|
|
|
|
/* No additional restrictions. */
|
|
|
|
break;
|
|
|
|
case YAMA_SCOPE_RELATIONAL:
|
2012-07-26 06:05:21 -06:00
|
|
|
rcu_read_lock();
|
2012-04-16 12:56:45 -06:00
|
|
|
if (!task_is_descendant(current, child) &&
|
|
|
|
!ptracer_exception_found(current, child) &&
|
2012-07-26 06:05:21 -06:00
|
|
|
!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
|
2012-04-16 12:56:45 -06:00
|
|
|
rc = -EPERM;
|
2012-07-26 06:05:21 -06:00
|
|
|
rcu_read_unlock();
|
2012-04-16 12:56:45 -06:00
|
|
|
break;
|
|
|
|
case YAMA_SCOPE_CAPABILITY:
|
2012-07-26 06:05:21 -06:00
|
|
|
rcu_read_lock();
|
|
|
|
if (!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
|
2012-04-16 12:56:45 -06:00
|
|
|
rc = -EPERM;
|
2012-07-26 06:05:21 -06:00
|
|
|
rcu_read_unlock();
|
2012-04-16 12:56:45 -06:00
|
|
|
break;
|
|
|
|
case YAMA_SCOPE_NO_ATTACH:
|
|
|
|
default:
|
|
|
|
rc = -EPERM;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
}
|
2011-12-21 13:17:04 -07:00
|
|
|
|
|
|
|
if (rc) {
|
2012-04-16 12:56:45 -06:00
|
|
|
printk_ratelimited(KERN_NOTICE
|
|
|
|
"ptrace of pid %d was attempted by: %s (pid %d)\n",
|
2012-08-15 12:41:55 -06:00
|
|
|
child->pid, current->comm, current->pid);
|
2011-12-21 13:17:04 -07:00
|
|
|
}
|
|
|
|
|
|
|
|
return rc;
|
|
|
|
}
|
|
|
|
|
2012-08-09 20:01:26 -06:00
|
|
|
/**
|
|
|
|
* 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.
|
|
|
|
*/
|
2012-09-04 14:32:13 -06:00
|
|
|
int yama_ptrace_traceme(struct task_struct *parent)
|
2012-08-09 20:01:26 -06:00
|
|
|
{
|
|
|
|
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:
|
2013-03-21 03:30:41 -06:00
|
|
|
if (!has_ns_capability(parent, current_user_ns(), CAP_SYS_PTRACE))
|
2012-08-09 20:01:26 -06:00
|
|
|
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",
|
2012-08-15 12:41:55 -06:00
|
|
|
current->pid, parent->comm, parent->pid);
|
2012-08-09 20:01:26 -06:00
|
|
|
}
|
|
|
|
|
|
|
|
return rc;
|
|
|
|
}
|
|
|
|
|
2012-09-04 14:32:13 -06:00
|
|
|
#ifndef CONFIG_SECURITY_YAMA_STACKED
|
2011-12-21 13:17:04 -07:00
|
|
|
static struct security_operations yama_ops = {
|
|
|
|
.name = "yama",
|
|
|
|
|
|
|
|
.ptrace_access_check = yama_ptrace_access_check,
|
2012-08-09 20:01:26 -06:00
|
|
|
.ptrace_traceme = yama_ptrace_traceme,
|
2011-12-21 13:17:04 -07:00
|
|
|
.task_prctl = yama_task_prctl,
|
|
|
|
.task_free = yama_task_free,
|
|
|
|
};
|
2012-09-04 14:32:13 -06:00
|
|
|
#endif
|
2011-12-21 13:17:04 -07:00
|
|
|
|
|
|
|
#ifdef CONFIG_SYSCTL
|
2012-04-16 12:56:45 -06:00
|
|
|
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;
|
|
|
|
}
|
|
|
|
|
2011-12-21 13:17:04 -07:00
|
|
|
static int zero;
|
2012-04-16 12:56:45 -06:00
|
|
|
static int max_scope = YAMA_SCOPE_NO_ATTACH;
|
2011-12-21 13:17:04 -07:00
|
|
|
|
|
|
|
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,
|
2012-04-16 12:56:45 -06:00
|
|
|
.proc_handler = yama_dointvec_minmax,
|
2011-12-21 13:17:04 -07:00
|
|
|
.extra1 = &zero,
|
2012-04-16 12:56:45 -06:00
|
|
|
.extra2 = &max_scope,
|
2011-12-21 13:17:04 -07:00
|
|
|
},
|
|
|
|
{ }
|
|
|
|
};
|
|
|
|
#endif /* CONFIG_SYSCTL */
|
|
|
|
|
|
|
|
static __init int yama_init(void)
|
|
|
|
{
|
2012-09-04 14:32:13 -06:00
|
|
|
#ifndef CONFIG_SECURITY_YAMA_STACKED
|
2011-12-21 13:17:04 -07:00
|
|
|
if (!security_module_enable(&yama_ops))
|
|
|
|
return 0;
|
2012-09-04 14:32:13 -06:00
|
|
|
#endif
|
2011-12-21 13:17:04 -07:00
|
|
|
|
|
|
|
printk(KERN_INFO "Yama: becoming mindful.\n");
|
|
|
|
|
2012-09-04 14:32:13 -06:00
|
|
|
#ifndef CONFIG_SECURITY_YAMA_STACKED
|
2011-12-21 13:17:04 -07:00
|
|
|
if (register_security(&yama_ops))
|
|
|
|
panic("Yama: kernel registration failed.\n");
|
2012-09-04 14:32:13 -06:00
|
|
|
#endif
|
2011-12-21 13:17:04 -07:00
|
|
|
|
|
|
|
#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);
|