/* * 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);