kernel/capability.c - maze/linux - Git at Google

 /*
  * linux/kernel/capability.c
  *
  * Copyright (C) 1997  Andrew Main <zefram@fysh.org>
  *
  * Integrated into 2.1.97+,  Andrew G. Morgan <morgan@kernel.org>
  * 30 May 2002:	Cleanup, Robert M. Love <rml@tech9.net>
  */

 #include <linux/capability.h>
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/pid_namespace.h>
 #include <asm/uaccess.h>

 /*
  * This lock protects task->cap_* for all tasks including current.
  * Locking rule: acquire this prior to tasklist_lock.
  */
 static DEFINE_SPINLOCK(task_capability_lock);

 /*
  * Leveraged for setting/resetting capabilities
  */

 const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
 const kernel_cap_t __cap_full_set = CAP_FULL_SET;
 const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;

 EXPORT_SYMBOL(__cap_empty_set);
 EXPORT_SYMBOL(__cap_full_set);
 EXPORT_SYMBOL(__cap_init_eff_set);

 /*
  * More recent versions of libcap are available from:
  *
  *   http://www.kernel.org/pub/linux/libs/security/linux-privs/
  */

 static void warn_legacy_capability_use(void)
 {
 	static int warned;
 	if (!warned) {
 		char name[sizeof(current->comm)];

 		printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
 		       " (legacy support in use)\n",
 		       get_task_comm(name, current));
 		warned = 1;
 	}
 }

 /*
  * Version 2 capabilities worked fine, but the linux/capability.h file
  * that accompanied their introduction encouraged their use without
  * the necessary user-space source code changes. As such, we have
  * created a version 3 with equivalent functionality to version 2, but
  * with a header change to protect legacy source code from using
  * version 2 when it wanted to use version 1. If your system has code
  * that trips the following warning, it is using version 2 specific
  * capabilities and may be doing so insecurely.
  *
  * The remedy is to either upgrade your version of libcap (to 2.10+,
  * if the application is linked against it), or recompile your
  * application with modern kernel headers and this warning will go
  * away.
  */

 static void warn_deprecated_v2(void)
 {
 	static int warned;

 	if (!warned) {
 		char name[sizeof(current->comm)];

 		printk(KERN_INFO "warning: `%s' uses deprecated v2"
 		       " capabilities in a way that may be insecure.\n",
 		       get_task_comm(name, current));
 		warned = 1;
 	}
 }

 /*
  * Version check. Return the number of u32s in each capability flag
  * array, or a negative value on error.
  */
 static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
 {
 	__u32 version;

 	if (get_user(version, &header->version))
 		return -EFAULT;

 	switch (version) {
 	case _LINUX_CAPABILITY_VERSION_1:
 		warn_legacy_capability_use();
 		*tocopy = _LINUX_CAPABILITY_U32S_1;
 		break;
 	case _LINUX_CAPABILITY_VERSION_2:
 		warn_deprecated_v2();
 		/*
 		 * fall through - v3 is otherwise equivalent to v2.
 		 */
 	case _LINUX_CAPABILITY_VERSION_3:
 		*tocopy = _LINUX_CAPABILITY_U32S_3;
 		break;
 	default:
 		if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
 			return -EFAULT;
 		return -EINVAL;
 	}

 	return 0;
 }

 /*
  * For sys_getproccap() and sys_setproccap(), any of the three
  * capability set pointers may be NULL -- indicating that that set is
  * uninteresting and/or not to be changed.
  */

 /**
  * sys_capget - get the capabilities of a given process.
  * @header: pointer to struct that contains capability version and
  *	target pid data
  * @dataptr: pointer to struct that contains the effective, permitted,
  *	and inheritable capabilities that are returned
  *
  * Returns 0 on success and < 0 on error.
  */
 asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
 {
 	int ret = 0;
 	pid_t pid;
 	struct task_struct *target;
 	unsigned tocopy;
 	kernel_cap_t pE, pI, pP;

 	ret = cap_validate_magic(header, &tocopy);
 	if (ret != 0)
 		return ret;

 	if (get_user(pid, &header->pid))
 		return -EFAULT;

 	if (pid < 0)
 		return -EINVAL;

 	spin_lock(&task_capability_lock);
 	read_lock(&tasklist_lock);

 	if (pid && pid != task_pid_vnr(current)) {
 		target = find_task_by_vpid(pid);
 		if (!target) {
 			ret = -ESRCH;
 			goto out;
 		}
 	} else
 		target = current;

 	ret = security_capget(target, &pE, &pI, &pP);

 out:
 	read_unlock(&tasklist_lock);
 	spin_unlock(&task_capability_lock);

 	if (!ret) {
 		struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 		unsigned i;

 		for (i = 0; i < tocopy; i++) {
 			kdata[i].effective = pE.cap[i];
 			kdata[i].permitted = pP.cap[i];
 			kdata[i].inheritable = pI.cap[i];
 		}

 		/*
 		 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
 		 * we silently drop the upper capabilities here. This
 		 * has the effect of making older libcap
 		 * implementations implicitly drop upper capability
 		 * bits when they perform a: capget/modify/capset
 		 * sequence.
 		 *
 		 * This behavior is considered fail-safe
 		 * behavior. Upgrading the application to a newer
 		 * version of libcap will enable access to the newer
 		 * capabilities.
 		 *
 		 * An alternative would be to return an error here
 		 * (-ERANGE), but that causes legacy applications to
 		 * unexpectidly fail; the capget/modify/capset aborts
 		 * before modification is attempted and the application
 		 * fails.
 		 */

 		if (copy_to_user(dataptr, kdata, tocopy
 				 * sizeof(struct __user_cap_data_struct))) {
 			return -EFAULT;
 		}
 	}

 	return ret;
 }

 /*
  * cap_set_pg - set capabilities for all processes in a given process
  * group.  We call this holding task_capability_lock and tasklist_lock.
  */
 static inline int cap_set_pg(int pgrp_nr, kernel_cap_t *effective,
 			      kernel_cap_t *inheritable,
 			      kernel_cap_t *permitted)
 {
 	struct task_struct *g, *target;
 	int ret = -EPERM;
 	int found = 0;
 	struct pid *pgrp;

 	pgrp = find_vpid(pgrp_nr);
 	do_each_pid_task(pgrp, PIDTYPE_PGID, g) {
 		target = g;
 		while_each_thread(g, target) {
 			if (!security_capset_check(target, effective,
 							inheritable,
 							permitted)) {
 				security_capset_set(target, effective,
 							inheritable,
 							permitted);
 				ret = 0;
 			}
 			found = 1;
 		}
 	} while_each_pid_task(pgrp, PIDTYPE_PGID, g);

 	if (!found)
 		ret = 0;
 	return ret;
 }

 /*
  * cap_set_all - set capabilities for all processes other than init
  * and self.  We call this holding task_capability_lock and tasklist_lock.
  */
 static inline int cap_set_all(kernel_cap_t *effective,
 			       kernel_cap_t *inheritable,
 			       kernel_cap_t *permitted)
 {
      struct task_struct *g, *target;
      int ret = -EPERM;
      int found = 0;

      do_each_thread(g, target) {
              if (target == current || is_container_init(target->group_leader))
                      continue;
              found = 1;
 	     if (security_capset_check(target, effective, inheritable,
 						permitted))
 		     continue;
 	     ret = 0;
 	     security_capset_set(target, effective, inheritable, permitted);
      } while_each_thread(g, target);

      if (!found)
 	     ret = 0;
      return ret;
 }

 /**
  * sys_capset - set capabilities for a process or a group of processes
  * @header: pointer to struct that contains capability version and
  *	target pid data
  * @data: pointer to struct that contains the effective, permitted,
  *	and inheritable capabilities
  *
  * Set capabilities for a given process, all processes, or all
  * processes in a given process group.
  *
  * The restrictions on setting capabilities are specified as:
  *
  * [pid is for the 'target' task.  'current' is the calling task.]
  *
  * I: any raised capabilities must be a subset of the (old current) permitted
  * P: any raised capabilities must be a subset of the (old current) permitted
  * E: must be set to a subset of (new target) permitted
  *
  * Returns 0 on success and < 0 on error.
  */
 asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
 {
 	struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 	unsigned i, tocopy;
 	kernel_cap_t inheritable, permitted, effective;
 	struct task_struct *target;
 	int ret;
 	pid_t pid;

 	ret = cap_validate_magic(header, &tocopy);
 	if (ret != 0)
 		return ret;

 	if (get_user(pid, &header->pid))
 		return -EFAULT;

 	if (pid && pid != task_pid_vnr(current) && !capable(CAP_SETPCAP))
 		return -EPERM;

 	if (copy_from_user(&kdata, data, tocopy
 			   * sizeof(struct __user_cap_data_struct))) {
 		return -EFAULT;
 	}

 	for (i = 0; i < tocopy; i++) {
 		effective.cap[i] = kdata[i].effective;
 		permitted.cap[i] = kdata[i].permitted;
 		inheritable.cap[i] = kdata[i].inheritable;
 	}
 	while (i < _KERNEL_CAPABILITY_U32S) {
 		effective.cap[i] = 0;
 		permitted.cap[i] = 0;
 		inheritable.cap[i] = 0;
 		i++;
 	}

 	spin_lock(&task_capability_lock);
 	read_lock(&tasklist_lock);

 	if (pid > 0 && pid != task_pid_vnr(current)) {
 		target = find_task_by_vpid(pid);
 		if (!target) {
 			ret = -ESRCH;
 			goto out;
 		}
 	} else
 		target = current;

 	ret = 0;

 	/* having verified that the proposed changes are legal,
 	   we now put them into effect. */
 	if (pid < 0) {
 		if (pid == -1)	/* all procs other than current and init */
 			ret = cap_set_all(&effective, &inheritable, &permitted);

 		else		/* all procs in process group */
 			ret = cap_set_pg(-pid, &effective, &inheritable,
 					 &permitted);
 	} else {
 		ret = security_capset_check(target, &effective, &inheritable,
 					    &permitted);
 		if (!ret)
 			security_capset_set(target, &effective, &inheritable,
 					    &permitted);
 	}

 out:
 	read_unlock(&tasklist_lock);
 	spin_unlock(&task_capability_lock);

 	return ret;
 }

 int __capable(struct task_struct *t, int cap)
 {
 	if (security_capable(t, cap) == 0) {
 		t->flags |= PF_SUPERPRIV;
 		return 1;
 	}
 	return 0;
 }

 int capable(int cap)
 {
 	return __capable(current, cap);
 }
 EXPORT_SYMBOL(capable);
	/*
	* linux/kernel/capability.c
	*
	* Copyright (C) 1997 Andrew Main <zefram@fysh.org>
	*
	* Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org>
	* 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
	*/

	#include <linux/capability.h>
	#include <linux/mm.h>
	#include <linux/module.h>
	#include <linux/security.h>
	#include <linux/syscalls.h>
	#include <linux/pid_namespace.h>
	#include <asm/uaccess.h>

	/*
	* This lock protects task->cap_* for all tasks including current.
	* Locking rule: acquire this prior to tasklist_lock.
	*/
	static DEFINE_SPINLOCK(task_capability_lock);

	/*
	* Leveraged for setting/resetting capabilities
	*/

	const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
	const kernel_cap_t __cap_full_set = CAP_FULL_SET;
	const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;

	EXPORT_SYMBOL(__cap_empty_set);
	EXPORT_SYMBOL(__cap_full_set);
	EXPORT_SYMBOL(__cap_init_eff_set);

	/*
	* More recent versions of libcap are available from:
	*
	* http://www.kernel.org/pub/linux/libs/security/linux-privs/
	*/

	static void warn_legacy_capability_use(void)
	{
	static int warned;
	if (!warned) {
	char name[sizeof(current->comm)];

	printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
	" (legacy support in use)\n",
	get_task_comm(name, current));
	warned = 1;
	}
	}

	/*
	* Version 2 capabilities worked fine, but the linux/capability.h file
	* that accompanied their introduction encouraged their use without
	* the necessary user-space source code changes. As such, we have
	* created a version 3 with equivalent functionality to version 2, but
	* with a header change to protect legacy source code from using
	* version 2 when it wanted to use version 1. If your system has code
	* that trips the following warning, it is using version 2 specific
	* capabilities and may be doing so insecurely.
	*
	* The remedy is to either upgrade your version of libcap (to 2.10+,
	* if the application is linked against it), or recompile your
	* application with modern kernel headers and this warning will go
	* away.
	*/

	static void warn_deprecated_v2(void)
	{
	static int warned;

	if (!warned) {
	char name[sizeof(current->comm)];

	printk(KERN_INFO "warning: `%s' uses deprecated v2"
	" capabilities in a way that may be insecure.\n",
	get_task_comm(name, current));
	warned = 1;
	}
	}

	/*
	* Version check. Return the number of u32s in each capability flag
	* array, or a negative value on error.
	*/
	static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
	{
	__u32 version;

	if (get_user(version, &header->version))
	return -EFAULT;

	switch (version) {
	case _LINUX_CAPABILITY_VERSION_1:
	warn_legacy_capability_use();
	*tocopy = _LINUX_CAPABILITY_U32S_1;
	break;
	case _LINUX_CAPABILITY_VERSION_2:
	warn_deprecated_v2();
	/*
	* fall through - v3 is otherwise equivalent to v2.
	*/
	case _LINUX_CAPABILITY_VERSION_3:
	*tocopy = _LINUX_CAPABILITY_U32S_3;
	break;
	default:
	if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
	return -EFAULT;
	return -EINVAL;
	}

	return 0;
	}

	/*
	* For sys_getproccap() and sys_setproccap(), any of the three
	* capability set pointers may be NULL -- indicating that that set is
	* uninteresting and/or not to be changed.
	*/

	/**
	* sys_capget - get the capabilities of a given process.
	* @header: pointer to struct that contains capability version and
	* target pid data
	* @dataptr: pointer to struct that contains the effective, permitted,
	* and inheritable capabilities that are returned
	*
	* Returns 0 on success and < 0 on error.
	*/
	asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
	{
	int ret = 0;
	pid_t pid;
	struct task_struct *target;
	unsigned tocopy;
	kernel_cap_t pE, pI, pP;

	ret = cap_validate_magic(header, &tocopy);
	if (ret != 0)
	return ret;

	if (get_user(pid, &header->pid))
	return -EFAULT;

	if (pid < 0)
	return -EINVAL;

	spin_lock(&task_capability_lock);
	read_lock(&tasklist_lock);

	if (pid && pid != task_pid_vnr(current)) {
	target = find_task_by_vpid(pid);
	if (!target) {
	ret = -ESRCH;
	goto out;
	}
	} else
	target = current;

	ret = security_capget(target, &pE, &pI, &pP);

	out:
	read_unlock(&tasklist_lock);
	spin_unlock(&task_capability_lock);

	if (!ret) {
	struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
	unsigned i;

	for (i = 0; i < tocopy; i++) {
	kdata[i].effective = pE.cap[i];
	kdata[i].permitted = pP.cap[i];
	kdata[i].inheritable = pI.cap[i];
	}

	/*
	* Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
	* we silently drop the upper capabilities here. This
	* has the effect of making older libcap
	* implementations implicitly drop upper capability
	* bits when they perform a: capget/modify/capset
	* sequence.
	*
	* This behavior is considered fail-safe
	* behavior. Upgrading the application to a newer
	* version of libcap will enable access to the newer
	* capabilities.
	*
	* An alternative would be to return an error here
	* (-ERANGE), but that causes legacy applications to
	* unexpectidly fail; the capget/modify/capset aborts
	* before modification is attempted and the application
	* fails.
	*/

	if (copy_to_user(dataptr, kdata, tocopy
	* sizeof(struct __user_cap_data_struct))) {
	return -EFAULT;
	}
	}

	return ret;
	}

	/*
	* cap_set_pg - set capabilities for all processes in a given process
	* group. We call this holding task_capability_lock and tasklist_lock.
	*/
	static inline int cap_set_pg(int pgrp_nr, kernel_cap_t *effective,
	kernel_cap_t *inheritable,
	kernel_cap_t *permitted)
	{
	struct task_struct g, target;
	int ret = -EPERM;
	int found = 0;
	struct pid *pgrp;

	pgrp = find_vpid(pgrp_nr);
	do_each_pid_task(pgrp, PIDTYPE_PGID, g) {
	target = g;
	while_each_thread(g, target) {
	if (!security_capset_check(target, effective,
	inheritable,
	permitted)) {
	security_capset_set(target, effective,
	inheritable,
	permitted);
	ret = 0;
	}
	found = 1;
	}
	} while_each_pid_task(pgrp, PIDTYPE_PGID, g);

	if (!found)
	ret = 0;
	return ret;
	}

	/*
	* cap_set_all - set capabilities for all processes other than init
	* and self. We call this holding task_capability_lock and tasklist_lock.
	*/
	static inline int cap_set_all(kernel_cap_t *effective,
	kernel_cap_t *inheritable,
	kernel_cap_t *permitted)
	{
	struct task_struct g, target;
	int ret = -EPERM;
	int found = 0;

	do_each_thread(g, target) {
	if (target == current \|\| is_container_init(target->group_leader))
	continue;
	found = 1;
	if (security_capset_check(target, effective, inheritable,
	permitted))
	continue;
	ret = 0;
	security_capset_set(target, effective, inheritable, permitted);
	} while_each_thread(g, target);

	if (!found)
	ret = 0;
	return ret;
	}

	/**
	* sys_capset - set capabilities for a process or a group of processes
	* @header: pointer to struct that contains capability version and
	* target pid data
	* @data: pointer to struct that contains the effective, permitted,
	* and inheritable capabilities
	*
	* Set capabilities for a given process, all processes, or all
	* processes in a given process group.
	*
	* The restrictions on setting capabilities are specified as:
	*
	* [pid is for the 'target' task. 'current' is the calling task.]
	*
	* I: any raised capabilities must be a subset of the (old current) permitted
	* P: any raised capabilities must be a subset of the (old current) permitted
	* E: must be set to a subset of (new target) permitted
	*
	* Returns 0 on success and < 0 on error.
	*/
	asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
	{
	struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
	unsigned i, tocopy;
	kernel_cap_t inheritable, permitted, effective;
	struct task_struct *target;
	int ret;
	pid_t pid;

	ret = cap_validate_magic(header, &tocopy);
	if (ret != 0)
	return ret;

	if (get_user(pid, &header->pid))
	return -EFAULT;

	if (pid && pid != task_pid_vnr(current) && !capable(CAP_SETPCAP))
	return -EPERM;

	if (copy_from_user(&kdata, data, tocopy
	* sizeof(struct __user_cap_data_struct))) {
	return -EFAULT;
	}

	for (i = 0; i < tocopy; i++) {
	effective.cap[i] = kdata[i].effective;
	permitted.cap[i] = kdata[i].permitted;
	inheritable.cap[i] = kdata[i].inheritable;
	}
	while (i < _KERNEL_CAPABILITY_U32S) {
	effective.cap[i] = 0;
	permitted.cap[i] = 0;
	inheritable.cap[i] = 0;
	i++;
	}

	spin_lock(&task_capability_lock);
	read_lock(&tasklist_lock);

	if (pid > 0 && pid != task_pid_vnr(current)) {
	target = find_task_by_vpid(pid);
	if (!target) {
	ret = -ESRCH;
	goto out;
	}
	} else
	target = current;

	ret = 0;

	/* having verified that the proposed changes are legal,
	we now put them into effect. */
	if (pid < 0) {
	if (pid == -1) /* all procs other than current and init */
	ret = cap_set_all(&effective, &inheritable, &permitted);

	else /* all procs in process group */
	ret = cap_set_pg(-pid, &effective, &inheritable,
	&permitted);
	} else {
	ret = security_capset_check(target, &effective, &inheritable,
	&permitted);
	if (!ret)
	security_capset_set(target, &effective, &inheritable,
	&permitted);
	}

	out:
	read_unlock(&tasklist_lock);
	spin_unlock(&task_capability_lock);

	return ret;
	}

	int __capable(struct task_struct *t, int cap)
	{
	if (security_capable(t, cap) == 0) {
	t->flags \|= PF_SUPERPRIV;
	return 1;
	}
	return 0;
	}

	int capable(int cap)
	{
	return __capable(current, cap);
	}
	EXPORT_SYMBOL(capable);