// SPDX-License-Identifier: GPL-2.0 /* * linux/ipc/util.c * Copyright (C) 1992 Krishna Balasubramanian * * Sep 1997 - Call suser() last after "normal" permission checks so we * get BSD style process accounting right. * Occurs in several places in the IPC code. * Chris Evans, * Nov 1999 - ipc helper functions, unified SMP locking * Manfred Spraul * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary(). * Mingming Cao * Mar 2006 - support for audit of ipc object properties * Dustin Kirkland * Jun 2006 - namespaces ssupport * OpenVZ, SWsoft Inc. * Pavel Emelianov * * General sysv ipc locking scheme: * rcu_read_lock() * obtain the ipc object (kern_ipc_perm) by looking up the id in an idr * tree. * - perform initial checks (capabilities, auditing and permission, * etc). * - perform read-only operations, such as STAT, INFO commands. * acquire the ipc lock (kern_ipc_perm.lock) through * ipc_lock_object() * - perform data updates, such as SET, RMID commands and * mechanism-specific operations (semop/semtimedop, * msgsnd/msgrcv, shmat/shmdt). * drop the ipc lock, through ipc_unlock_object(). * rcu_read_unlock() * * The ids->rwsem must be taken when: * - creating, removing and iterating the existing entries in ipc * identifier sets. * - iterating through files under /proc/sysvipc/ * * Note that sems have a special fast path that avoids kern_ipc_perm.lock - * see sem_lock(). */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "util.h" struct ipc_proc_iface { const char *path; const char *header; int ids; int (*show)(struct seq_file *, void *); }; /** * ipc_init - initialise ipc subsystem * * The various sysv ipc resources (semaphores, messages and shared * memory) are initialised. * * A callback routine is registered into the memory hotplug notifier * chain: since msgmni scales to lowmem this callback routine will be * called upon successful memory add / remove to recompute msmgni. */ static int __init ipc_init(void) { int err_sem, err_msg; err_sem = sem_init(); WARN(err_sem, "ipc: sysv sem_init failed: %d\n", err_sem); err_msg = msg_init(); WARN(err_msg, "ipc: sysv msg_init failed: %d\n", err_msg); shm_init(); return err_msg ? err_msg : err_sem; } device_initcall(ipc_init); static const struct rhashtable_params ipc_kht_params = { .head_offset = offsetof(struct kern_ipc_perm, khtnode), .key_offset = offsetof(struct kern_ipc_perm, key), .key_len = FIELD_SIZEOF(struct kern_ipc_perm, key), .locks_mul = 1, .automatic_shrinking = true, }; /** * ipc_init_ids - initialise ipc identifiers * @ids: ipc identifier set * * Set up the sequence range to use for the ipc identifier range (limited * below IPCMNI) then initialise the keys hashtable and ids idr. */ int ipc_init_ids(struct ipc_ids *ids) { int err; ids->in_use = 0; ids->seq = 0; ids->next_id = -1; init_rwsem(&ids->rwsem); err = rhashtable_init(&ids->key_ht, &ipc_kht_params); if (err) return err; idr_init(&ids->ipcs_idr); ids->tables_initialized = true; return 0; } #ifdef CONFIG_PROC_FS static const struct file_operations sysvipc_proc_fops; /** * ipc_init_proc_interface - create a proc interface for sysipc types using a seq_file interface. * @path: Path in procfs * @header: Banner to be printed at the beginning of the file. * @ids: ipc id table to iterate. * @show: show routine. */ void __init ipc_init_proc_interface(const char *path, const char *header, int ids, int (*show)(struct seq_file *, void *)) { struct proc_dir_entry *pde; struct ipc_proc_iface *iface; if (IS_ENABLED(CONFIG_PROC_STRIPPED)) return; iface = kmalloc(sizeof(*iface), GFP_KERNEL); if (!iface) return; iface->path = path; iface->header = header; iface->ids = ids; iface->show = show; pde = proc_create_data(path, S_IRUGO, /* world readable */ NULL, /* parent dir */ &sysvipc_proc_fops, iface); if (!pde) kfree(iface); } #endif /** * ipc_findkey - find a key in an ipc identifier set * @ids: ipc identifier set * @key: key to find * * Returns the locked pointer to the ipc structure if found or NULL * otherwise. If key is found ipc points to the owning ipc structure * * Called with writer ipc_ids.rwsem held. */ static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key) { struct kern_ipc_perm *ipcp = NULL; if (likely(ids->tables_initialized)) ipcp = rhashtable_lookup_fast(&ids->key_ht, &key, ipc_kht_params); if (ipcp) { rcu_read_lock(); ipc_lock_object(ipcp); return ipcp; } return NULL; } /** * ipc_get_maxid - get the last assigned id * @ids: ipc identifier set * * Called with ipc_ids.rwsem held. */ int ipc_get_maxid(struct ipc_ids *ids) { struct kern_ipc_perm *ipc; int max_id = -1; int total, id; if (ids->in_use == 0) return -1; if (ids->in_use == IPCMNI) return IPCMNI - 1; /* Look for the last assigned id */ total = 0; for (id = 0; id < IPCMNI && total < ids->in_use; id++) { ipc = idr_find(&ids->ipcs_idr, id); if (ipc != NULL) { max_id = id; total++; } } return max_id; } /** * ipc_addid - add an ipc identifier * @ids: ipc identifier set * @new: new ipc permission set * @size: limit for the number of used ids * * Add an entry 'new' to the ipc ids idr. The permissions object is * initialised and the first free entry is set up and the id assigned * is returned. The 'new' entry is returned in a locked state on success. * On failure the entry is not locked and a negative err-code is returned. * * Called with writer ipc_ids.rwsem held. */ int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size) { kuid_t euid; kgid_t egid; int id, err; int next_id = ids->next_id; if (size > IPCMNI) size = IPCMNI; if (!ids->tables_initialized || ids->in_use >= size) return -ENOSPC; idr_preload(GFP_KERNEL); refcount_set(&new->refcount, 1); spin_lock_init(&new->lock); new->deleted = false; rcu_read_lock(); spin_lock(&new->lock); current_euid_egid(&euid, &egid); new->cuid = new->uid = euid; new->gid = new->cgid = egid; id = idr_alloc(&ids->ipcs_idr, new, (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0, GFP_NOWAIT); idr_preload_end(); if (id >= 0 && new->key != IPC_PRIVATE) { err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode, ipc_kht_params); if (err < 0) { idr_remove(&ids->ipcs_idr, id); id = err; } } if (id < 0) { spin_unlock(&new->lock); rcu_read_unlock(); return id; } ids->in_use++; if (next_id < 0) { new->seq = ids->seq++; if (ids->seq > IPCID_SEQ_MAX) ids->seq = 0; } else { new->seq = ipcid_to_seqx(next_id); ids->next_id = -1; } new->id = ipc_buildid(id, new->seq); return id; } /** * ipcget_new - create a new ipc object * @ns: ipc namespace * @ids: ipc identifier set * @ops: the actual creation routine to call * @params: its parameters * * This routine is called by sys_msgget, sys_semget() and sys_shmget() * when the key is IPC_PRIVATE. */ static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids, const struct ipc_ops *ops, struct ipc_params *params) { int err; down_write(&ids->rwsem); err = ops->getnew(ns, params); up_write(&ids->rwsem); return err; } /** * ipc_check_perms - check security and permissions for an ipc object * @ns: ipc namespace * @ipcp: ipc permission set * @ops: the actual security routine to call * @params: its parameters * * This routine is called by sys_msgget(), sys_semget() and sys_shmget() * when the key is not IPC_PRIVATE and that key already exists in the * ds IDR. * * On success, the ipc id is returned. * * It is called with ipc_ids.rwsem and ipcp->lock held. */ static int ipc_check_perms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, const struct ipc_ops *ops, struct ipc_params *params) { int err; if (ipcperms(ns, ipcp, params->flg)) err = -EACCES; else { err = ops->associate(ipcp, params->flg); if (!err) err = ipcp->id; } return err; } /** * ipcget_public - get an ipc object or create a new one * @ns: ipc namespace * @ids: ipc identifier set * @ops: the actual creation routine to call * @params: its parameters * * This routine is called by sys_msgget, sys_semget() and sys_shmget() * when the key is not IPC_PRIVATE. * It adds a new entry if the key is not found and does some permission * / security checkings if the key is found. * * On success, the ipc id is returned. */ static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, const struct ipc_ops *ops, struct ipc_params *params) { struct kern_ipc_perm *ipcp; int flg = params->flg; int err; /* * Take the lock as a writer since we are potentially going to add * a new entry + read locks are not "upgradable" */ down_write(&ids->rwsem); ipcp = ipc_findkey(ids, params->key); if (ipcp == NULL) { /* key not used */ if (!(flg & IPC_CREAT)) err = -ENOENT; else err = ops->getnew(ns, params); } else { /* ipc object has been locked by ipc_findkey() */ if (flg & IPC_CREAT && flg & IPC_EXCL) err = -EEXIST; else { err = 0; if (ops->more_checks) err = ops->more_checks(ipcp, params); if (!err) /* * ipc_check_perms returns the IPC id on * success */ err = ipc_check_perms(ns, ipcp, ops, params); } ipc_unlock(ipcp); } up_write(&ids->rwsem); return err; } /** * ipc_kht_remove - remove an ipc from the key hashtable * @ids: ipc identifier set * @ipcp: ipc perm structure containing the key to remove * * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held * before this function is called, and remain locked on the exit. */ static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp) { if (ipcp->key != IPC_PRIVATE) rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode, ipc_kht_params); } /** * ipc_rmid - remove an ipc identifier * @ids: ipc identifier set * @ipcp: ipc perm structure containing the identifier to remove * * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held * before this function is called, and remain locked on the exit. */ void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp) { int lid = ipcid_to_idx(ipcp->id); idr_remove(&ids->ipcs_idr, lid); ipc_kht_remove(ids, ipcp); ids->in_use--; ipcp->deleted = true; } /** * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE * @ids: ipc identifier set * @ipcp: ipc perm structure containing the key to modify * * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held * before this function is called, and remain locked on the exit. */ void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp) { ipc_kht_remove(ids, ipcp); ipcp->key = IPC_PRIVATE; } int ipc_rcu_getref(struct kern_ipc_perm *ptr) { return refcount_inc_not_zero(&ptr->refcount); } void ipc_rcu_putref(struct kern_ipc_perm *ptr, void (*func)(struct rcu_head *head)) { if (!refcount_dec_and_test(&ptr->refcount)) return; call_rcu(&ptr->rcu, func); } /** * ipcperms - check ipc permissions * @ns: ipc namespace * @ipcp: ipc permission set * @flag: desired permission set * * Check user, group, other permissions for access * to ipc resources. return 0 if allowed * * @flag will most probably be 0 or ``S_...UGO`` from */ int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag) { kuid_t euid = current_euid(); int requested_mode, granted_mode; audit_ipc_obj(ipcp); requested_mode = (flag >> 6) | (flag >> 3) | flag; granted_mode = ipcp->mode; if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)) granted_mode >>= 6; else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid)) granted_mode >>= 3; /* is there some bit set in requested_mode but not in granted_mode? */ if ((requested_mode & ~granted_mode & 0007) && !ns_capable(ns->user_ns, CAP_IPC_OWNER)) return -1; return security_ipc_permission(ipcp, flag); } /* * Functions to convert between the kern_ipc_perm structure and the * old/new ipc_perm structures */ /** * kernel_to_ipc64_perm - convert kernel ipc permissions to user * @in: kernel permissions * @out: new style ipc permissions * * Turn the kernel object @in into a set of permissions descriptions * for returning to userspace (@out). */ void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out) { out->key = in->key; out->uid = from_kuid_munged(current_user_ns(), in->uid); out->gid = from_kgid_munged(current_user_ns(), in->gid); out->cuid = from_kuid_munged(current_user_ns(), in->cuid); out->cgid = from_kgid_munged(current_user_ns(), in->cgid); out->mode = in->mode; out->seq = in->seq; } /** * ipc64_perm_to_ipc_perm - convert new ipc permissions to old * @in: new style ipc permissions * @out: old style ipc permissions * * Turn the new style permissions object @in into a compatibility * object and store it into the @out pointer. */ void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out) { out->key = in->key; SET_UID(out->uid, in->uid); SET_GID(out->gid, in->gid); SET_UID(out->cuid, in->cuid); SET_GID(out->cgid, in->cgid); out->mode = in->mode; out->seq = in->seq; } /** * ipc_obtain_object_idr * @ids: ipc identifier set * @id: ipc id to look for * * Look for an id in the ipc ids idr and return associated ipc object. * * Call inside the RCU critical section. * The ipc object is *not* locked on exit. */ struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id) { struct kern_ipc_perm *out; int lid = ipcid_to_idx(id); if (unlikely(!ids->tables_initialized)) return ERR_PTR(-EINVAL); out = idr_find(&ids->ipcs_idr, lid); if (!out) return ERR_PTR(-EINVAL); return out; } /** * ipc_lock - lock an ipc structure without rwsem held * @ids: ipc identifier set * @id: ipc id to look for * * Look for an id in the ipc ids idr and lock the associated ipc object. * * The ipc object is locked on successful exit. */ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id) { struct kern_ipc_perm *out; rcu_read_lock(); out = ipc_obtain_object_idr(ids, id); if (IS_ERR(out)) goto err; spin_lock(&out->lock); /* * ipc_rmid() may have already freed the ID while ipc_lock() * was spinning: here verify that the structure is still valid. * Upon races with RMID, return -EIDRM, thus indicating that * the ID points to a removed identifier. */ if (ipc_valid_object(out)) return out; spin_unlock(&out->lock); out = ERR_PTR(-EIDRM); err: rcu_read_unlock(); return out; } /** * ipc_obtain_object_check * @ids: ipc identifier set * @id: ipc id to look for * * Similar to ipc_obtain_object_idr() but also checks * the ipc object reference counter. * * Call inside the RCU critical section. * The ipc object is *not* locked on exit. */ struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id) { struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id); if (IS_ERR(out)) goto out; if (ipc_checkid(out, id)) return ERR_PTR(-EINVAL); out: return out; } /** * ipcget - Common sys_*get() code * @ns: namespace * @ids: ipc identifier set * @ops: operations to be called on ipc object creation, permission checks * and further checks * @params: the parameters needed by the previous operations. * * Common routine called by sys_msgget(), sys_semget() and sys_shmget(). */ int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids, const struct ipc_ops *ops, struct ipc_params *params) { if (params->key == IPC_PRIVATE) return ipcget_new(ns, ids, ops, params); else return ipcget_public(ns, ids, ops, params); } /** * ipc_update_perm - update the permissions of an ipc object * @in: the permission given as input. * @out: the permission of the ipc to set. */ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out) { kuid_t uid = make_kuid(current_user_ns(), in->uid); kgid_t gid = make_kgid(current_user_ns(), in->gid); if (!uid_valid(uid) || !gid_valid(gid)) return -EINVAL; out->uid = uid; out->gid = gid; out->mode = (out->mode & ~S_IRWXUGO) | (in->mode & S_IRWXUGO); return 0; } /** * ipcctl_pre_down_nolock - retrieve an ipc and check permissions for some IPC_XXX cmd * @ns: ipc namespace * @ids: the table of ids where to look for the ipc * @id: the id of the ipc to retrieve * @cmd: the cmd to check * @perm: the permission to set * @extra_perm: one extra permission parameter used by msq * * This function does some common audit and permissions check for some IPC_XXX * cmd and is called from semctl_down, shmctl_down and msgctl_down. * It must be called without any lock held and: * * - retrieves the ipc with the given id in the given table. * - performs some audit and permission check, depending on the given cmd * - returns a pointer to the ipc object or otherwise, the corresponding * error. * * Call holding the both the rwsem and the rcu read lock. */ struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns, struct ipc_ids *ids, int id, int cmd, struct ipc64_perm *perm, int extra_perm) { kuid_t euid; int err = -EPERM; struct kern_ipc_perm *ipcp; ipcp = ipc_obtain_object_check(ids, id); if (IS_ERR(ipcp)) { err = PTR_ERR(ipcp); goto err; } audit_ipc_obj(ipcp); if (cmd == IPC_SET) audit_ipc_set_perm(extra_perm, perm->uid, perm->gid, perm->mode); euid = current_euid(); if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid) || ns_capable(ns->user_ns, CAP_SYS_ADMIN)) return ipcp; /* successful lookup */ err: return ERR_PTR(err); } #ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION /** * ipc_parse_version - ipc call version * @cmd: pointer to command * * Return IPC_64 for new style IPC and IPC_OLD for old style IPC. * The @cmd value is turned from an encoding command and version into * just the command code. */ int ipc_parse_version(int *cmd) { if (*cmd & IPC_64) { *cmd ^= IPC_64; return IPC_64; } else { return IPC_OLD; } } #endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */ #ifdef CONFIG_PROC_FS struct ipc_proc_iter { struct ipc_namespace *ns; struct ipc_proc_iface *iface; }; /* * This routine locks the ipc structure found at least at position pos. */ static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos, loff_t *new_pos) { struct kern_ipc_perm *ipc; int total, id; total = 0; for (id = 0; id < pos && total < ids->in_use; id++) { ipc = idr_find(&ids->ipcs_idr, id); if (ipc != NULL) total++; } ipc = NULL; if (total >= ids->in_use) goto out; for (; pos < IPCMNI; pos++) { ipc = idr_find(&ids->ipcs_idr, pos); if (ipc != NULL) { rcu_read_lock(); ipc_lock_object(ipc); break; } } out: *new_pos = pos + 1; return ipc; } static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos) { struct ipc_proc_iter *iter = s->private; struct ipc_proc_iface *iface = iter->iface; struct kern_ipc_perm *ipc = it; /* If we had an ipc id locked before, unlock it */ if (ipc && ipc != SEQ_START_TOKEN) ipc_unlock(ipc); return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos); } /* * File positions: pos 0 -> header, pos n -> ipc id = n - 1. * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START. */ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos) { struct ipc_proc_iter *iter = s->private; struct ipc_proc_iface *iface = iter->iface; struct ipc_ids *ids; ids = &iter->ns->ids[iface->ids]; /* * Take the lock - this will be released by the corresponding * call to stop(). */ down_read(&ids->rwsem); /* pos < 0 is invalid */ if (*pos < 0) return NULL; /* pos == 0 means header */ if (*pos == 0) return SEQ_START_TOKEN; /* Find the (pos-1)th ipc */ return sysvipc_find_ipc(ids, *pos - 1, pos); } static void sysvipc_proc_stop(struct seq_file *s, void *it) { struct kern_ipc_perm *ipc = it; struct ipc_proc_iter *iter = s->private; struct ipc_proc_iface *iface = iter->iface; struct ipc_ids *ids; /* If we had a locked structure, release it */ if (ipc && ipc != SEQ_START_TOKEN) ipc_unlock(ipc); ids = &iter->ns->ids[iface->ids]; /* Release the lock we took in start() */ up_read(&ids->rwsem); } static int sysvipc_proc_show(struct seq_file *s, void *it) { struct ipc_proc_iter *iter = s->private; struct ipc_proc_iface *iface = iter->iface; if (it == SEQ_START_TOKEN) { seq_puts(s, iface->header); return 0; } return iface->show(s, it); } static const struct seq_operations sysvipc_proc_seqops = { .start = sysvipc_proc_start, .stop = sysvipc_proc_stop, .next = sysvipc_proc_next, .show = sysvipc_proc_show, }; static int sysvipc_proc_open(struct inode *inode, struct file *file) { struct ipc_proc_iter *iter; iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter)); if (!iter) return -ENOMEM; iter->iface = PDE_DATA(inode); iter->ns = get_ipc_ns(current->nsproxy->ipc_ns); return 0; } static int sysvipc_proc_release(struct inode *inode, struct file *file) { struct seq_file *seq = file->private_data; struct ipc_proc_iter *iter = seq->private; put_ipc_ns(iter->ns); return seq_release_private(inode, file); } static const struct file_operations sysvipc_proc_fops = { .open = sysvipc_proc_open, .read = seq_read, .llseek = seq_lseek, .release = sysvipc_proc_release, }; #endif /* CONFIG_PROC_FS */