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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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#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>
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);
#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){ pr_info_once("warning: `%s' uses 32-bit capabilities (legacy support in use)\n", current->comm);}
/* * 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){ pr_info_once("warning: `%s' uses deprecated v2 capabilities in a way that may be insecure\n", current->comm);}
/* * 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(); fallthrough; /* 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))) { const 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; struct __user_cap_data_struct kdata[2];
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) return ret;
/* * Annoying legacy format with 64-bit capabilities exposed * as two sets of 32-bit fields, so we need to split the * capability values up. */ kdata[0].effective = pE.val; kdata[1].effective = pE.val >> 32; kdata[0].permitted = pP.val; kdata[1].permitted = pP.val >> 32; kdata[0].inheritable = pI.val; kdata[1].inheritable = pI.val >> 32;
/* * 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(kdata[0]))) return -EFAULT;
return 0;}
static kernel_cap_t mk_kernel_cap(u32 low, u32 high){ return (kernel_cap_t) { (low | ((u64)high << 32)) & CAP_VALID_MASK };}
/** * 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[2] = { { 0, }, }; unsigned 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;
effective = mk_kernel_cap(kdata[0].effective, kdata[1].effective); permitted = mk_kernel_cap(kdata[0].permitted, kdata[1].permitted); inheritable = mk_kernel_cap(kdata[0].inheritable, kdata[1].inheritable);
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, CAP_OPT_NONE); rcu_read_unlock();
return (ret == 0);}
/** * 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(__task_cred(t), ns, cap, CAP_OPT_NOAUDIT); 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);}EXPORT_SYMBOL(has_capability_noaudit);
static bool ns_capable_common(struct user_namespace *ns, int cap, unsigned int opts){ int capable;
if (unlikely(!cap_valid(cap))) { pr_crit("capable() called with invalid cap=%u\n", cap); BUG(); }
capable = security_capable(current_cred(), ns, cap, opts); if (capable == 0) { current->flags |= PF_SUPERPRIV; return true; } return false;}
/** * 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, CAP_OPT_NONE);}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, CAP_OPT_NOAUDIT);}EXPORT_SYMBOL(ns_capable_noaudit);
/** * ns_capable_setid - Determine if the current task has a superior capability * in effect, while signalling that this check is being done from within a * setid or setgroups syscall. * @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_setid(struct user_namespace *ns, int cap){ return ns_capable_common(ns, cap, CAP_OPT_INSETID);}EXPORT_SYMBOL(ns_capable_setid);
/** * 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);#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, CAP_OPT_NONE) == 0) return true;
return false;}EXPORT_SYMBOL(file_ns_capable);
/** * privileged_wrt_inode_uidgid - Do capabilities in the namespace work over the inode? * @ns: The user namespace in question * @idmap: idmap of the mount @inode was found from * @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, struct mnt_idmap *idmap, const struct inode *inode){ return vfsuid_has_mapping(ns, i_uid_into_vfsuid(idmap, inode)) && vfsgid_has_mapping(ns, i_gid_into_vfsgid(idmap, inode));}
/** * capable_wrt_inode_uidgid - Check nsown_capable and uid and gid mapped * @idmap: idmap of the mount @inode was found from * @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(struct mnt_idmap *idmap, const struct inode *inode, int cap){ struct user_namespace *ns = current_user_ns();
return ns_capable(ns, cap) && privileged_wrt_inode_uidgid(ns, idmap, inode);}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(cred, ns, CAP_SYS_PTRACE, CAP_OPT_NOAUDIT); rcu_read_unlock(); return (ret == 0);}