kernel/capability.c - 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/audit.h>
 #include <linux/capability.h>
 #include <linux/mm.h>
 #include <linux/export.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/pid_namespace.h>
 #include <linux/user_namespace.h>
 #include <asm/uaccess.h>

 /*
  * Leveraged for setting/resetting capabilities
  */

 const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;

 EXPORT_SYMBOL(__cap_empty_set);

 int file_caps_enabled = 1;

 static int __init file_caps_disable(char *str)
 {
 	file_caps_enabled = 0;
 	return 1;
 }
 __setup("no_file_caps", file_caps_disable);

 /*
  * 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;
 }

 /*
  * The only thing that can change the capabilities of the current
  * process is the current process. As such, we can't be in this code
  * at the same time as we are in the process of setting capabilities
  * in this process. The net result is that we can limit our use of
  * locks to when we are reading the caps of another process.
  */
 static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
 				     kernel_cap_t *pIp, kernel_cap_t *pPp)
 {
 	int ret;

 	if (pid && (pid != task_pid_vnr(current))) {
 		struct task_struct *target;

 		rcu_read_lock();

 		target = find_task_by_vpid(pid);
 		if (!target)
 			ret = -ESRCH;
 		else
 			ret = security_capget(target, pEp, pIp, pPp);

 		rcu_read_unlock();
 	} else
 		ret = security_capget(current, pEp, pIp, pPp);

 	return ret;
 }

 /**
  * 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.
  */
 SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
 {
 	int ret = 0;
 	pid_t pid;
 	unsigned tocopy;
 	kernel_cap_t pE, pI, pP;

 	ret = cap_validate_magic(header, &tocopy);
 	if ((dataptr == NULL) || (ret != 0))
 		return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;

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

 	if (pid < 0)
 		return -EINVAL;

 	ret = cap_get_target_pid(pid, &pE, &pI, &pP);
 	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;
 }

 /**
  * 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 the current process only.  The ability to any other
  * process(es) has been deprecated and removed.
  *
  * The restrictions on setting capabilities are specified as:
  *
  * I: any raised capabilities must be a subset of the old permitted
  * P: any raised capabilities must be a subset of the old permitted
  * E: must be set to a subset of new permitted
  *
  * Returns 0 on success and < 0 on error.
  */
 SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
 {
 	struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
 	unsigned i, tocopy, copybytes;
 	kernel_cap_t inheritable, permitted, effective;
 	struct cred *new;
 	int ret;
 	pid_t pid;

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

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

 	/* may only affect current now */
 	if (pid != 0 && pid != task_pid_vnr(current))
 		return -EPERM;

 	copybytes = tocopy * sizeof(struct __user_cap_data_struct);
 	if (copybytes > sizeof(kdata))
 		return -EFAULT;

 	if (copy_from_user(&kdata, data, copybytes))
 		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++;
 	}

 	new = prepare_creds();
 	if (!new)
 		return -ENOMEM;

 	ret = security_capset(new, current_cred(),
 			      &effective, &inheritable, &permitted);
 	if (ret < 0)
 		goto error;

 	audit_log_capset(pid, new, current_cred());

 	return commit_creds(new);

 error:
 	abort_creds(new);
 	return ret;
 }

 /**
  * has_ns_capability - Does a task have a capability in a specific user ns
  * @t: The task in question
  * @ns: target user namespace
  * @cap: The capability to be tested for
  *
  * Return true if the specified task has the given superior capability
  * currently in effect to the specified user namespace, false if not.
  *
  * Note that this does not set PF_SUPERPRIV on the task.
  */
 bool has_ns_capability(struct task_struct *t,
 		       struct user_namespace *ns, int cap)
 {
 	int ret;

 	rcu_read_lock();
 	ret = security_capable(__task_cred(t), ns, cap);
 	rcu_read_unlock();

 	return (ret == 0);
 }

 /**
  * has_capability - Does a task have a capability in init_user_ns
  * @t: The task in question
  * @cap: The capability to be tested for
  *
  * Return true if the specified task has the given superior capability
  * currently in effect to the initial user namespace, false if not.
  *
  * Note that this does not set PF_SUPERPRIV on the task.
  */
 bool has_capability(struct task_struct *t, int cap)
 {
 	return has_ns_capability(t, &init_user_ns, cap);
 }

 /**
  * has_ns_capability_noaudit - Does a task have a capability (unaudited)
  * in a specific user ns.
  * @t: The task in question
  * @ns: target user namespace
  * @cap: The capability to be tested for
  *
  * Return true if the specified task has the given superior capability
  * currently in effect to the specified user namespace, false if not.
  * Do not write an audit message for the check.
  *
  * Note that this does not set PF_SUPERPRIV on the task.
  */
 bool has_ns_capability_noaudit(struct task_struct *t,
 			       struct user_namespace *ns, int cap)
 {
 	int ret;

 	rcu_read_lock();
 	ret = security_capable_noaudit(__task_cred(t), ns, cap);
 	rcu_read_unlock();

 	return (ret == 0);
 }

 /**
  * has_capability_noaudit - Does a task have a capability (unaudited) in the
  * initial user ns
  * @t: The task in question
  * @cap: The capability to be tested for
  *
  * Return true if the specified task has the given superior capability
  * currently in effect to init_user_ns, false if not.  Don't write an
  * audit message for the check.
  *
  * Note that this does not set PF_SUPERPRIV on the task.
  */
 bool has_capability_noaudit(struct task_struct *t, int cap)
 {
 	return has_ns_capability_noaudit(t, &init_user_ns, cap);
 }

 /**
  * ns_capable - Determine if the current task has a superior capability in effect
  * @ns:  The usernamespace we want the capability in
  * @cap: The capability to be tested for
  *
  * Return true if the current task has the given superior capability currently
  * available for use, false if not.
  *
  * This sets PF_SUPERPRIV on the task if the capability is available on the
  * assumption that it's about to be used.
  */
 bool ns_capable(struct user_namespace *ns, int cap)
 {
 	if (unlikely(!cap_valid(cap))) {
 		printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
 		BUG();
 	}

 	if (security_capable(current_cred(), ns, cap) == 0) {
 		current->flags |= PF_SUPERPRIV;
 		return true;
 	}
 	return false;
 }
 EXPORT_SYMBOL(ns_capable);

 /**
  * capable - Determine if the current task has a superior capability in effect
  * @cap: The capability to be tested for
  *
  * Return true if the current task has the given superior capability currently
  * available for use, false if not.
  *
  * This sets PF_SUPERPRIV on the task if the capability is available on the
  * assumption that it's about to be used.
  */
 bool capable(int cap)
 {
 	return ns_capable(&init_user_ns, cap);
 }
 EXPORT_SYMBOL(capable);

 /**
  * nsown_capable - Check superior capability to one's own user_ns
  * @cap: The capability in question
  *
  * Return true if the current task has the given superior capability
  * targeted at its own user namespace.
  */
 bool nsown_capable(int cap)
 {
 	return ns_capable(current_user_ns(), cap);
 }
	/*
	* 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/audit.h>
	#include <linux/capability.h>
	#include <linux/mm.h>
	#include <linux/export.h>
	#include <linux/security.h>
	#include <linux/syscalls.h>
	#include <linux/pid_namespace.h>
	#include <linux/user_namespace.h>
	#include <asm/uaccess.h>

	/*
	* Leveraged for setting/resetting capabilities
	*/

	const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;

	EXPORT_SYMBOL(__cap_empty_set);

	int file_caps_enabled = 1;

	static int __init file_caps_disable(char *str)
	{
	file_caps_enabled = 0;
	return 1;
	}
	__setup("no_file_caps", file_caps_disable);

	/*
	* 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;
	}

	/*
	* The only thing that can change the capabilities of the current
	* process is the current process. As such, we can't be in this code
	* at the same time as we are in the process of setting capabilities
	* in this process. The net result is that we can limit our use of
	* locks to when we are reading the caps of another process.
	*/
	static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
	kernel_cap_t pIp, kernel_cap_t pPp)
	{
	int ret;

	if (pid && (pid != task_pid_vnr(current))) {
	struct task_struct *target;

	rcu_read_lock();

	target = find_task_by_vpid(pid);
	if (!target)
	ret = -ESRCH;
	else
	ret = security_capget(target, pEp, pIp, pPp);

	rcu_read_unlock();
	} else
	ret = security_capget(current, pEp, pIp, pPp);

	return ret;
	}

	/**
	* 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.
	*/
	SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
	{
	int ret = 0;
	pid_t pid;
	unsigned tocopy;
	kernel_cap_t pE, pI, pP;

	ret = cap_validate_magic(header, &tocopy);
	if ((dataptr == NULL) \|\| (ret != 0))
	return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;

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

	if (pid < 0)
	return -EINVAL;

	ret = cap_get_target_pid(pid, &pE, &pI, &pP);
	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;
	}

	/**
	* 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 the current process only. The ability to any other
	* process(es) has been deprecated and removed.
	*
	* The restrictions on setting capabilities are specified as:
	*
	* I: any raised capabilities must be a subset of the old permitted
	* P: any raised capabilities must be a subset of the old permitted
	* E: must be set to a subset of new permitted
	*
	* Returns 0 on success and < 0 on error.
	*/
	SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
	{
	struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
	unsigned i, tocopy, copybytes;
	kernel_cap_t inheritable, permitted, effective;
	struct cred *new;
	int ret;
	pid_t pid;

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

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

	/* may only affect current now */
	if (pid != 0 && pid != task_pid_vnr(current))
	return -EPERM;

	copybytes = tocopy * sizeof(struct __user_cap_data_struct);
	if (copybytes > sizeof(kdata))
	return -EFAULT;

	if (copy_from_user(&kdata, data, copybytes))
	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++;
	}

	new = prepare_creds();
	if (!new)
	return -ENOMEM;

	ret = security_capset(new, current_cred(),
	&effective, &inheritable, &permitted);
	if (ret < 0)
	goto error;

	audit_log_capset(pid, new, current_cred());

	return commit_creds(new);

	error:
	abort_creds(new);
	return ret;
	}

	/**
	* has_ns_capability - Does a task have a capability in a specific user ns
	* @t: The task in question
	* @ns: target user namespace
	* @cap: The capability to be tested for
	*
	* Return true if the specified task has the given superior capability
	* currently in effect to the specified user namespace, false if not.
	*
	* Note that this does not set PF_SUPERPRIV on the task.
	*/
	bool has_ns_capability(struct task_struct *t,
	struct user_namespace *ns, int cap)
	{
	int ret;

	rcu_read_lock();
	ret = security_capable(__task_cred(t), ns, cap);
	rcu_read_unlock();

	return (ret == 0);
	}

	/**
	* has_capability - Does a task have a capability in init_user_ns
	* @t: The task in question
	* @cap: The capability to be tested for
	*
	* Return true if the specified task has the given superior capability
	* currently in effect to the initial user namespace, false if not.
	*
	* Note that this does not set PF_SUPERPRIV on the task.
	*/
	bool has_capability(struct task_struct *t, int cap)
	{
	return has_ns_capability(t, &init_user_ns, cap);
	}

	/**
	* has_ns_capability_noaudit - Does a task have a capability (unaudited)
	* in a specific user ns.
	* @t: The task in question
	* @ns: target user namespace
	* @cap: The capability to be tested for
	*
	* Return true if the specified task has the given superior capability
	* currently in effect to the specified user namespace, false if not.
	* Do not write an audit message for the check.
	*
	* Note that this does not set PF_SUPERPRIV on the task.
	*/
	bool has_ns_capability_noaudit(struct task_struct *t,
	struct user_namespace *ns, int cap)
	{
	int ret;

	rcu_read_lock();
	ret = security_capable_noaudit(__task_cred(t), ns, cap);
	rcu_read_unlock();

	return (ret == 0);
	}

	/**
	* has_capability_noaudit - Does a task have a capability (unaudited) in the
	* initial user ns
	* @t: The task in question
	* @cap: The capability to be tested for
	*
	* Return true if the specified task has the given superior capability
	* currently in effect to init_user_ns, false if not. Don't write an
	* audit message for the check.
	*
	* Note that this does not set PF_SUPERPRIV on the task.
	*/
	bool has_capability_noaudit(struct task_struct *t, int cap)
	{
	return has_ns_capability_noaudit(t, &init_user_ns, cap);
	}

	/**
	* ns_capable - Determine if the current task has a superior capability in effect
	* @ns: The usernamespace we want the capability in
	* @cap: The capability to be tested for
	*
	* Return true if the current task has the given superior capability currently
	* available for use, false if not.
	*
	* This sets PF_SUPERPRIV on the task if the capability is available on the
	* assumption that it's about to be used.
	*/
	bool ns_capable(struct user_namespace *ns, int cap)
	{
	if (unlikely(!cap_valid(cap))) {
	printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
	BUG();
	}

	if (security_capable(current_cred(), ns, cap) == 0) {
	current->flags \|= PF_SUPERPRIV;
	return true;
	}
	return false;
	}
	EXPORT_SYMBOL(ns_capable);

	/**
	* capable - Determine if the current task has a superior capability in effect
	* @cap: The capability to be tested for
	*
	* Return true if the current task has the given superior capability currently
	* available for use, false if not.
	*
	* This sets PF_SUPERPRIV on the task if the capability is available on the
	* assumption that it's about to be used.
	*/
	bool capable(int cap)
	{
	return ns_capable(&init_user_ns, cap);
	}
	EXPORT_SYMBOL(capable);

	/**
	* nsown_capable - Check superior capability to one's own user_ns
	* @cap: The capability in question
	*
	* Return true if the current task has the given superior capability
	* targeted at its own user namespace.
	*/
	bool nsown_capable(int cap)
	{
	return ns_capable(current_user_ns(), cap);
	}