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![Al Viro](/assets/img/avatar_default.png)
* no allocations * return void * don't duplicate checked for dummy context Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
315 lines
8 KiB
C
315 lines
8 KiB
C
/*
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* linux/kernel/capability.c
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*
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* Copyright (C) 1997 Andrew Main <zefram@fysh.org>
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*
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* Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org>
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* 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
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*/
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#include <linux/audit.h>
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#include <linux/capability.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <linux/pid_namespace.h>
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#include <asm/uaccess.h>
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#include "cred-internals.h"
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/*
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* Leveraged for setting/resetting capabilities
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*/
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const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
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const kernel_cap_t __cap_full_set = CAP_FULL_SET;
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const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;
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EXPORT_SYMBOL(__cap_empty_set);
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EXPORT_SYMBOL(__cap_full_set);
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EXPORT_SYMBOL(__cap_init_eff_set);
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#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
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int file_caps_enabled = 1;
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static int __init file_caps_disable(char *str)
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{
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file_caps_enabled = 0;
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return 1;
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}
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__setup("no_file_caps", file_caps_disable);
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#endif
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/*
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* More recent versions of libcap are available from:
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*
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* http://www.kernel.org/pub/linux/libs/security/linux-privs/
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*/
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static void warn_legacy_capability_use(void)
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{
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static int warned;
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if (!warned) {
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char name[sizeof(current->comm)];
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printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
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" (legacy support in use)\n",
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get_task_comm(name, current));
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warned = 1;
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}
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}
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/*
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* Version 2 capabilities worked fine, but the linux/capability.h file
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* that accompanied their introduction encouraged their use without
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* the necessary user-space source code changes. As such, we have
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* created a version 3 with equivalent functionality to version 2, but
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* with a header change to protect legacy source code from using
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* version 2 when it wanted to use version 1. If your system has code
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* that trips the following warning, it is using version 2 specific
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* capabilities and may be doing so insecurely.
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*
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* The remedy is to either upgrade your version of libcap (to 2.10+,
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* if the application is linked against it), or recompile your
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* application with modern kernel headers and this warning will go
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* away.
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*/
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static void warn_deprecated_v2(void)
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{
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static int warned;
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if (!warned) {
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char name[sizeof(current->comm)];
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printk(KERN_INFO "warning: `%s' uses deprecated v2"
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" capabilities in a way that may be insecure.\n",
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get_task_comm(name, current));
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warned = 1;
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}
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}
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/*
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* Version check. Return the number of u32s in each capability flag
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* array, or a negative value on error.
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*/
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static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
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{
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__u32 version;
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if (get_user(version, &header->version))
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return -EFAULT;
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switch (version) {
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case _LINUX_CAPABILITY_VERSION_1:
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warn_legacy_capability_use();
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*tocopy = _LINUX_CAPABILITY_U32S_1;
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break;
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case _LINUX_CAPABILITY_VERSION_2:
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warn_deprecated_v2();
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/*
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* fall through - v3 is otherwise equivalent to v2.
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*/
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case _LINUX_CAPABILITY_VERSION_3:
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*tocopy = _LINUX_CAPABILITY_U32S_3;
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break;
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default:
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if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
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return -EFAULT;
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return -EINVAL;
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}
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return 0;
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}
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/*
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* The only thing that can change the capabilities of the current
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* process is the current process. As such, we can't be in this code
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* at the same time as we are in the process of setting capabilities
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* in this process. The net result is that we can limit our use of
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* locks to when we are reading the caps of another process.
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*/
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static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
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kernel_cap_t *pIp, kernel_cap_t *pPp)
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{
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int ret;
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if (pid && (pid != task_pid_vnr(current))) {
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struct task_struct *target;
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read_lock(&tasklist_lock);
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target = find_task_by_vpid(pid);
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if (!target)
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ret = -ESRCH;
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else
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ret = security_capget(target, pEp, pIp, pPp);
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read_unlock(&tasklist_lock);
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} else
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ret = security_capget(current, pEp, pIp, pPp);
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return ret;
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}
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/**
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* sys_capget - get the capabilities of a given process.
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* @header: pointer to struct that contains capability version and
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* target pid data
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* @dataptr: pointer to struct that contains the effective, permitted,
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* and inheritable capabilities that are returned
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*
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* Returns 0 on success and < 0 on error.
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*/
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asmlinkage long sys_capget(cap_user_header_t header, cap_user_data_t dataptr)
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{
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int ret = 0;
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pid_t pid;
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unsigned tocopy;
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kernel_cap_t pE, pI, pP;
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ret = cap_validate_magic(header, &tocopy);
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if (ret != 0)
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return ret;
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if (get_user(pid, &header->pid))
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return -EFAULT;
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if (pid < 0)
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return -EINVAL;
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ret = cap_get_target_pid(pid, &pE, &pI, &pP);
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if (!ret) {
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struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
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unsigned i;
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for (i = 0; i < tocopy; i++) {
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kdata[i].effective = pE.cap[i];
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kdata[i].permitted = pP.cap[i];
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kdata[i].inheritable = pI.cap[i];
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}
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/*
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* Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
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* we silently drop the upper capabilities here. This
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* has the effect of making older libcap
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* implementations implicitly drop upper capability
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* bits when they perform a: capget/modify/capset
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* sequence.
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*
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* This behavior is considered fail-safe
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* behavior. Upgrading the application to a newer
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* version of libcap will enable access to the newer
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* capabilities.
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*
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* An alternative would be to return an error here
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* (-ERANGE), but that causes legacy applications to
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* unexpectidly fail; the capget/modify/capset aborts
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* before modification is attempted and the application
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* fails.
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*/
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if (copy_to_user(dataptr, kdata, tocopy
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* sizeof(struct __user_cap_data_struct))) {
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return -EFAULT;
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}
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}
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return ret;
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}
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/**
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* sys_capset - set capabilities for a process or (*) a group of processes
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* @header: pointer to struct that contains capability version and
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* target pid data
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* @data: pointer to struct that contains the effective, permitted,
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* and inheritable capabilities
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*
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* Set capabilities for the current process only. The ability to any other
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* process(es) has been deprecated and removed.
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*
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* The restrictions on setting capabilities are specified as:
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*
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* I: any raised capabilities must be a subset of the old permitted
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* P: any raised capabilities must be a subset of the old permitted
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* E: must be set to a subset of new permitted
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*
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* Returns 0 on success and < 0 on error.
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*/
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asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
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{
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struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
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unsigned i, tocopy;
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kernel_cap_t inheritable, permitted, effective;
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struct cred *new;
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int ret;
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pid_t pid;
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ret = cap_validate_magic(header, &tocopy);
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if (ret != 0)
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return ret;
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if (get_user(pid, &header->pid))
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return -EFAULT;
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/* may only affect current now */
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if (pid != 0 && pid != task_pid_vnr(current))
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return -EPERM;
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if (copy_from_user(&kdata, data,
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tocopy * sizeof(struct __user_cap_data_struct)))
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return -EFAULT;
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for (i = 0; i < tocopy; i++) {
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effective.cap[i] = kdata[i].effective;
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permitted.cap[i] = kdata[i].permitted;
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inheritable.cap[i] = kdata[i].inheritable;
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}
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while (i < _KERNEL_CAPABILITY_U32S) {
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effective.cap[i] = 0;
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permitted.cap[i] = 0;
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inheritable.cap[i] = 0;
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i++;
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}
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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ret = security_capset(new, current_cred(),
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&effective, &inheritable, &permitted);
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if (ret < 0)
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goto error;
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audit_log_capset(pid, new, current_cred());
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return commit_creds(new);
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error:
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abort_creds(new);
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return ret;
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}
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/**
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* capable - Determine if the current task has a superior capability in effect
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* @cap: The capability to be tested for
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*
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* Return true if the current task has the given superior capability currently
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* available for use, false if not.
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*
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* This sets PF_SUPERPRIV on the task if the capability is available on the
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* assumption that it's about to be used.
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*/
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int capable(int cap)
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{
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if (unlikely(!cap_valid(cap))) {
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printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
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BUG();
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}
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if (has_capability(current, cap)) {
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current->flags |= PF_SUPERPRIV;
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return 1;
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}
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return 0;
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}
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EXPORT_SYMBOL(capable);
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