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/*
* 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;
}
#ifndef CONFIG_SECURITY_FILE_CAPABILITIES
/*
* Without filesystem capability support, we nominally support one process
* setting the capabilities of another
*/
static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
kernel_cap_t *pIp, kernel_cap_t *pPp)
{
struct task_struct *target;
int ret;
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, pEp, pIp, pPp);
out:
read_unlock(&tasklist_lock);
spin_unlock(&task_capability_lock);
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;
spin_lock(&task_capability_lock);
read_lock(&tasklist_lock);
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);
read_unlock(&tasklist_lock);
spin_unlock(&task_capability_lock);
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;
spin_lock(&task_capability_lock);
read_lock(&tasklist_lock);
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);
read_unlock(&tasklist_lock);
spin_unlock(&task_capability_lock);
if (!found)
ret = 0;
return ret;
}
/*
* Given the target pid does not refer to the current process we
* need more elaborate support... (This support is not present when
* filesystem capabilities are configured.)
*/
static inline int do_sys_capset_other_tasks(pid_t pid, kernel_cap_t *effective,
kernel_cap_t *inheritable,
kernel_cap_t *permitted)
{
struct task_struct *target;
int ret;
if (!capable(CAP_SETPCAP))
return -EPERM;
if (pid == -1) /* all procs other than current and init */
return cap_set_all(effective, inheritable, permitted);
else if (pid < 0) /* all procs in process group */
return cap_set_pg(-pid, effective, inheritable, permitted);
/* target != current */
spin_lock(&task_capability_lock);
read_lock(&tasklist_lock);
target = find_task_by_vpid(pid);
if (!target)
ret = -ESRCH;
else {
ret = security_capset_check(target, effective, inheritable,
permitted);
/* having verified that the proposed changes are legal,
we now put them into effect. */
if (!ret)
security_capset_set(target, effective, inheritable,
permitted);
}
read_unlock(&tasklist_lock);
spin_unlock(&task_capability_lock);
return ret;
}
#else /* ie., def CONFIG_SECURITY_FILE_CAPABILITIES */
/*
* If we have configured with filesystem capability support, then 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;
spin_lock(&task_capability_lock);
read_lock(&tasklist_lock);
target = find_task_by_vpid(pid);
if (!target)
ret = -ESRCH;
else
ret = security_capget(target, pEp, pIp, pPp);
read_unlock(&tasklist_lock);
spin_unlock(&task_capability_lock);
} else
ret = security_capget(current, pEp, pIp, pPp);
return ret;
}
/*
* With filesystem capability support configured, the kernel does not
* permit the changing of capabilities in one process by another
* process. (CAP_SETPCAP has much less broad semantics when configured
* this way.)
*/
static inline int do_sys_capset_other_tasks(pid_t pid,
kernel_cap_t *effective,
kernel_cap_t *inheritable,
kernel_cap_t *permitted)
{
return -EPERM;
}
#endif /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */
/*
* Atomically modify the effective capabilities returning the original
* value. No permission check is performed here - it is assumed that the
* caller is permitted to set the desired effective capabilities.
*/
kernel_cap_t cap_set_effective(const kernel_cap_t pE_new)
{
kernel_cap_t pE_old;
spin_lock(&task_capability_lock);
pE_old = current->cap_effective;
current->cap_effective = pE_new;
spin_unlock(&task_capability_lock);
return pE_old;
}
EXPORT_SYMBOL(cap_set_effective);
/**
* 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;
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;
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 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;
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 (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++;
}
if (pid && (pid != task_pid_vnr(current)))
ret = do_sys_capset_other_tasks(pid, &effective, &inheritable,
&permitted);
else {
/*
* This lock is required even when filesystem
* capability support is configured - it protects the
* sys_capget() call from returning incorrect data in
* the case that the targeted process is not the
* current one.
*/
spin_lock(&task_capability_lock);
ret = security_capset_check(current, &effective, &inheritable,
&permitted);
/*
* Having verified that the proposed changes are
* legal, we now put them into effect.
*/
if (!ret)
security_capset_set(current, &effective, &inheritable,
&permitted);
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);
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