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Diffstat (limited to 'ipc/util.c')
| -rw-r--r-- | ipc/util.c | 931 |
1 files changed, 931 insertions, 0 deletions
diff --git a/ipc/util.c b/ipc/util.c new file mode 100644 index 000000000..05cb9de66 --- /dev/null +++ b/ipc/util.c @@ -0,0 +1,931 @@ +// 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, <chris@ferret.lmh.ox.ac.uk> + * Nov 1999 - ipc helper functions, unified SMP locking + * Manfred Spraul <manfred@colorfullife.com> + * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary(). + * Mingming Cao <cmm@us.ibm.com> + * Mar 2006 - support for audit of ipc object properties + * Dustin Kirkland <dustin.kirkland@us.ibm.com> + * Jun 2006 - namespaces ssupport + * OpenVZ, SWsoft Inc. + * Pavel Emelianov <xemul@openvz.org> + * + * 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 INFO command, that + * do not demand atomicity + * acquire the ipc lock (kern_ipc_perm.lock) through + * ipc_lock_object() + * - perform read-only operations that demand atomicity, + * such as STAT command. + * - 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 <linux/mm.h> +#include <linux/shm.h> +#include <linux/init.h> +#include <linux/msg.h> +#include <linux/vmalloc.h> +#include <linux/slab.h> +#include <linux/notifier.h> +#include <linux/capability.h> +#include <linux/highuid.h> +#include <linux/security.h> +#include <linux/rcupdate.h> +#include <linux/workqueue.h> +#include <linux/seq_file.h> +#include <linux/proc_fs.h> +#include <linux/audit.h> +#include <linux/nsproxy.h> +#include <linux/rwsem.h> +#include <linux/memory.h> +#include <linux/ipc_namespace.h> +#include <linux/rhashtable.h> +#include <linux/log2.h> + +#include <asm/unistd.h> + +#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) +{ + proc_mkdir("sysvipc", NULL); + sem_init(); + msg_init(); + shm_init(); + + return 0; +} +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 = sizeof_field(struct kern_ipc_perm, key), + .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 ipc_mni) then initialise the keys hashtable and ids idr. + */ +void ipc_init_ids(struct ipc_ids *ids) +{ + ids->in_use = 0; + ids->seq = 0; + init_rwsem(&ids->rwsem); + rhashtable_init(&ids->key_ht, &ipc_kht_params); + idr_init(&ids->ipcs_idr); + ids->max_idx = -1; + ids->last_idx = -1; +#ifdef CONFIG_CHECKPOINT_RESTORE + ids->next_id = -1; +#endif +} + +#ifdef CONFIG_PROC_FS +static const struct proc_ops sysvipc_proc_ops; +/** + * 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; + + 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_ops, + 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; + + ipcp = rhashtable_lookup_fast(&ids->key_ht, &key, + ipc_kht_params); + if (!ipcp) + return NULL; + + rcu_read_lock(); + ipc_lock_object(ipcp); + return ipcp; +} + +/* + * Insert new IPC object into idr tree, and set sequence number and id + * in the correct order. + * Especially: + * - the sequence number must be set before inserting the object into the idr, + * because the sequence number is accessed without a lock. + * - the id can/must be set after inserting the object into the idr. + * All accesses must be done after getting kern_ipc_perm.lock. + * + * The caller must own kern_ipc_perm.lock.of the new object. + * On error, the function returns a (negative) error code. + * + * To conserve sequence number space, especially with extended ipc_mni, + * the sequence number is incremented only when the returned ID is less than + * the last one. + */ +static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new) +{ + int idx, next_id = -1; + +#ifdef CONFIG_CHECKPOINT_RESTORE + next_id = ids->next_id; + ids->next_id = -1; +#endif + + /* + * As soon as a new object is inserted into the idr, + * ipc_obtain_object_idr() or ipc_obtain_object_check() can find it, + * and the lockless preparations for ipc operations can start. + * This means especially: permission checks, audit calls, allocation + * of undo structures, ... + * + * Thus the object must be fully initialized, and if something fails, + * then the full tear-down sequence must be followed. + * (i.e.: set new->deleted, reduce refcount, call_rcu()) + */ + + if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */ + int max_idx; + + max_idx = max(ids->in_use*3/2, ipc_min_cycle); + max_idx = min(max_idx, ipc_mni); + + /* allocate the idx, with a NULL struct kern_ipc_perm */ + idx = idr_alloc_cyclic(&ids->ipcs_idr, NULL, 0, max_idx, + GFP_NOWAIT); + + if (idx >= 0) { + /* + * idx got allocated successfully. + * Now calculate the sequence number and set the + * pointer for real. + */ + if (idx <= ids->last_idx) { + ids->seq++; + if (ids->seq >= ipcid_seq_max()) + ids->seq = 0; + } + ids->last_idx = idx; + + new->seq = ids->seq; + /* no need for smp_wmb(), this is done + * inside idr_replace, as part of + * rcu_assign_pointer + */ + idr_replace(&ids->ipcs_idr, new, idx); + } + } else { + new->seq = ipcid_to_seqx(next_id); + idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id), + 0, GFP_NOWAIT); + } + if (idx >= 0) + new->id = (new->seq << ipcmni_seq_shift()) + idx; + return idx; +} + +/** + * ipc_addid - add an ipc identifier + * @ids: ipc identifier set + * @new: new ipc permission set + * @limit: 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 index 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. + * The caller must use ipc_rcu_putref() to free the identifier. + * + * Called with writer ipc_ids.rwsem held. + */ +int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit) +{ + kuid_t euid; + kgid_t egid; + int idx, err; + + /* 1) Initialize the refcount so that ipc_rcu_putref works */ + refcount_set(&new->refcount, 1); + + if (limit > ipc_mni) + limit = ipc_mni; + + if (ids->in_use >= limit) + return -ENOSPC; + + idr_preload(GFP_KERNEL); + + spin_lock_init(&new->lock); + rcu_read_lock(); + spin_lock(&new->lock); + + current_euid_egid(&euid, &egid); + new->cuid = new->uid = euid; + new->gid = new->cgid = egid; + + new->deleted = false; + + idx = ipc_idr_alloc(ids, new); + idr_preload_end(); + + if (idx >= 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, idx); + idx = err; + } + } + if (idx < 0) { + new->deleted = true; + spin_unlock(&new->lock); + rcu_read_unlock(); + return idx; + } + + ids->in_use++; + if (idx > ids->max_idx) + ids->max_idx = idx; + return idx; +} + +/** + * 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) + WARN_ON_ONCE(rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode, + ipc_kht_params)); +} + +/** + * ipc_search_maxidx - search for the highest assigned index + * @ids: ipc identifier set + * @limit: known upper limit for highest assigned index + * + * The function determines the highest assigned index in @ids. It is intended + * to be called when ids->max_idx needs to be updated. + * Updating ids->max_idx is necessary when the current highest index ipc + * object is deleted. + * If no ipc object is allocated, then -1 is returned. + * + * ipc_ids.rwsem needs to be held by the caller. + */ +static int ipc_search_maxidx(struct ipc_ids *ids, int limit) +{ + int tmpidx; + int i; + int retval; + + i = ilog2(limit+1); + + retval = 0; + for (; i >= 0; i--) { + tmpidx = retval | (1<<i); + /* + * "0" is a possible index value, thus search using + * e.g. 15,7,3,1,0 instead of 16,8,4,2,1. + */ + tmpidx = tmpidx-1; + if (idr_get_next(&ids->ipcs_idr, &tmpidx)) + retval |= (1<<i); + } + return retval - 1; +} + +/** + * 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 idx = ipcid_to_idx(ipcp->id); + + WARN_ON_ONCE(idr_remove(&ids->ipcs_idr, idx) != ipcp); + ipc_kht_remove(ids, ipcp); + ids->in_use--; + ipcp->deleted = true; + + if (unlikely(idx == ids->max_idx)) { + idx = ids->max_idx-1; + if (idx >= 0) + idx = ipc_search_maxidx(ids, idx); + ids->max_idx = idx; + } +} + +/** + * 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; +} + +bool 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 <linux/stat.h> + */ +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 idx = ipcid_to_idx(id); + + out = idr_find(&ids->ipcs_idr, idx); + if (!out) + return ERR_PTR(-EINVAL); + + 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 + * sequence number. + * + * 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_obtain_check - retrieve an ipc object and check permissions + * @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: + * - retrieves the ipc object 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_obtain_check(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 pid_namespace *pid_ns; + struct ipc_proc_iface *iface; +}; + +struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s) +{ + struct ipc_proc_iter *iter = s->private; + return iter->pid_ns; +} + +/** + * sysvipc_find_ipc - Find and lock the ipc structure based on seq pos + * @ids: ipc identifier set + * @pos: expected position + * + * The function finds an ipc structure, based on the sequence file + * position @pos. If there is no ipc structure at position @pos, then + * the successor is selected. + * If a structure is found, then it is locked (both rcu_read_lock() and + * ipc_lock_object()) and @pos is set to the position needed to locate + * the found ipc structure. + * If nothing is found (i.e. EOF), @pos is not modified. + * + * The function returns the found ipc structure, or NULL at EOF. + */ +static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t *pos) +{ + int tmpidx; + struct kern_ipc_perm *ipc; + + /* convert from position to idr index -> "-1" */ + tmpidx = *pos - 1; + + ipc = idr_get_next(&ids->ipcs_idr, &tmpidx); + if (ipc != NULL) { + rcu_read_lock(); + ipc_lock_object(ipc); + + /* convert from idr index to position -> "+1" */ + *pos = tmpidx + 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); + + /* Next -> search for *pos+1 */ + (*pos)++; + return sysvipc_find_ipc(&iter->ns->ids[iface->ids], pos); +} + +/* + * File positions: pos 0 -> header, pos n -> ipc idx = 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; + + /* Otherwise return the correct ipc structure */ + return sysvipc_find_ipc(ids, 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); + iter->pid_ns = get_pid_ns(task_active_pid_ns(current)); + + 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); + put_pid_ns(iter->pid_ns); + return seq_release_private(inode, file); +} + +static const struct proc_ops sysvipc_proc_ops = { + .proc_flags = PROC_ENTRY_PERMANENT, + .proc_open = sysvipc_proc_open, + .proc_read = seq_read, + .proc_lseek = seq_lseek, + .proc_release = sysvipc_proc_release, +}; +#endif /* CONFIG_PROC_FS */ |