cregit-Linux how code gets into the kernel

Release 4.17 kernel/capability.c

Directory: kernel
// SPDX-License-Identifier: GPL-2.0
/*
 * 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>
 */


#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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 <linux/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; }

Contributors

PersonTokensPropCommitsCommitProp
Serge E. Hallyn18100.00%1100.00%
Total18100.00%1100.00%

__setup("no_file_caps", file_caps_disable); #ifdef CONFIG_MULTIUSER /* * 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) { char name[sizeof(current->comm)]; pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n", get_task_comm(name, current)); }

Contributors

PersonTokensPropCommitsCommitProp
Andrew G. Morgan2993.55%150.00%
Joe Perches26.45%150.00%
Total31100.00%2100.00%

/* * 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) { char name[sizeof(current->comm)]; pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n", get_task_comm(name, current)); }

Contributors

PersonTokensPropCommitsCommitProp
Andrew G. Morgan2993.55%150.00%
Joe Perches26.45%150.00%
Total31100.00%2100.00%

/* * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Andrew G. Morgan4447.31%233.33%
Linus Torvalds (pre-git)4346.24%233.33%
Robert Love66.45%233.33%
Total93100.00%6100.00%

/* * 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; }

Contributors

PersonTokensPropCommitsCommitProp
Andrew G. Morgan9595.96%150.00%
Thomas Gleixner44.04%150.00%
Total99100.00%2100.00%

/** * 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 * unexpectedly 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++; } effective.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK; new = prepare_creds(); if (!new) return -ENOMEM; ret = security_capset(new, current_cred(), &effective, &inheritable, &permitted); if (ret < 0) goto error; audit_log_capset(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); }

Contributors

PersonTokensPropCommitsCommitProp
Serge E. Hallyn2756.25%133.33%
Eric Paris2143.75%266.67%
Total48100.00%3100.00%

/** * 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); }

Contributors

PersonTokensPropCommitsCommitProp
Serge E. Hallyn1979.17%150.00%
Eric Paris520.83%150.00%
Total24100.00%2100.00%

EXPORT_SYMBOL(has_capability); /** * 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); }

Contributors

PersonTokensPropCommitsCommitProp
Serge E. Hallyn2756.25%133.33%
Eric Paris2143.75%266.67%
Total48100.00%3100.00%

/** * 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); }

Contributors

PersonTokensPropCommitsCommitProp
Serge E. Hallyn1458.33%133.33%
Eric Paris937.50%133.33%
Chris Wright14.17%133.33%
Total24100.00%3100.00%


static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit) { int capable; if (unlikely(!cap_valid(cap))) { pr_crit("capable() called with invalid cap=%u\n", cap); BUG(); } capable = audit ? security_capable(current_cred(), ns, cap) : security_capable_noaudit(current_cred(), ns, cap); if (capable == 0) { current->flags |= PF_SUPERPRIV; return true; } return false; }

Contributors

PersonTokensPropCommitsCommitProp
Tyler Hicks2629.89%111.11%
Chris Wright2427.59%222.22%
Eric Paris2124.14%222.22%
Serge E. Hallyn910.34%111.11%
Linus Torvalds55.75%111.11%
David Howells11.15%111.11%
Joe Perches11.15%111.11%
Total87100.00%9100.00%

/** * 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) { return ns_capable_common(ns, cap, true); }

Contributors

PersonTokensPropCommitsCommitProp
Tyler Hicks23100.00%1100.00%
Total23100.00%1100.00%

EXPORT_SYMBOL(ns_capable); /** * ns_capable_noaudit - Determine if the current task has a superior capability * (unaudited) 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_noaudit(struct user_namespace *ns, int cap) { return ns_capable_common(ns, cap, false); }

Contributors

PersonTokensPropCommitsCommitProp
Tyler Hicks23100.00%1100.00%
Total23100.00%1100.00%

EXPORT_SYMBOL(ns_capable_noaudit); /** * 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); }

Contributors

PersonTokensPropCommitsCommitProp
Iulia Manda17100.00%1100.00%
Total17100.00%1100.00%

EXPORT_SYMBOL(capable); #endif /* CONFIG_MULTIUSER */ /** * file_ns_capable - Determine if the file's opener had a capability in effect * @file: The file we want to check * @ns: The usernamespace we want the capability in * @cap: The capability to be tested for * * Return true if task that opened the file had a capability in effect * when the file was opened. * * This does not set PF_SUPERPRIV because the caller may not * actually be privileged. */
bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap) { if (WARN_ON_ONCE(!cap_valid(cap))) return false; if (security_capable(file->f_cred, ns, cap) == 0) return true; return false; }

Contributors

PersonTokensPropCommitsCommitProp
Linus Torvalds54100.00%1100.00%
Total54100.00%1100.00%

EXPORT_SYMBOL(file_ns_capable); /** * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode? * @ns: The user namespace in question * @inode: The inode in question * * Return true if the inode uid and gid are within the namespace. */
bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct inode *inode) { return kuid_has_mapping(ns, inode->i_uid) && kgid_has_mapping(ns, inode->i_gid); }

Contributors

PersonTokensPropCommitsCommitProp
Eric W. Biedermann35100.00%1100.00%
Total35100.00%1100.00%

/** * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped * @inode: The inode in question * @cap: The capability in question * * Return true if the current task has the given capability targeted at * its own user namespace and that the given inode's uid and gid are * mapped into the current user namespace. */
bool capable_wrt_inode_uidgid(const struct inode *inode, int cap) { struct user_namespace *ns = current_user_ns(); return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, inode); }

Contributors

PersonTokensPropCommitsCommitProp
Eric W. Biedermann3594.59%375.00%
Andrew Lutomirski25.41%125.00%
Total37100.00%4100.00%

EXPORT_SYMBOL(capable_wrt_inode_uidgid); /** * ptracer_capable - Determine if the ptracer holds CAP_SYS_PTRACE in the namespace * @tsk: The task that may be ptraced * @ns: The user namespace to search for CAP_SYS_PTRACE in * * Return true if the task that is ptracing the current task had CAP_SYS_PTRACE * in the specified user namespace. */
bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns) { int ret = 0; /* An absent tracer adds no restrictions */ const struct cred *cred; rcu_read_lock(); cred = rcu_dereference(tsk->ptracer_cred); if (cred) ret = security_capable_noaudit(cred, ns, CAP_SYS_PTRACE); rcu_read_unlock(); return (ret == 0); }

Contributors

PersonTokensPropCommitsCommitProp
Eric W. Biedermann64100.00%1100.00%
Total64100.00%1100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
Andrew G. Morgan52036.78%59.80%
Serge E. Hallyn15110.68%59.80%
Eric W. Biedermann1369.62%47.84%
Eric Paris1299.12%713.73%
Linus Torvalds (pre-git)1047.36%23.92%
Tyler Hicks795.59%11.96%
Linus Torvalds664.67%35.88%
David Howells624.38%35.88%
Iulia Manda292.05%11.96%
Chris Wright271.91%23.92%
Arjan van de Ven261.84%11.96%
Heiko Carstens241.70%11.96%
Joe Perches120.85%11.96%
Robert Love100.71%23.92%
Greg Kroah-Hartman90.64%35.88%
Jike Song50.35%11.96%
Andrew Lutomirski40.28%11.96%
Thomas Gleixner40.28%11.96%
Dwight Engen40.28%11.96%
Ingo Molnar30.21%11.96%
Arnd Bergmann30.21%11.96%
Randy Dunlap30.21%11.96%
Arnaldo Carvalho de Melo20.14%11.96%
Fabian Frederick10.07%11.96%
Paul Gortmaker10.07%11.96%
Total1414100.00%51100.00%
Directory: kernel
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