// 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, <[email protected]> * Nov 1999 - ipc helper functions, unified SMP locking * Manfred Spraul <[email protected]> * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary(). * Mingming Cao <[email protected]> * Mar 2006 - support for audit of ipc object properties * Dustin Kirkland <[email protected]> * Jun 2006 - namespaces ssupport * OpenVZ, SWsoft Inc. * Pavel Emelianov <[email protected]> * * 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 { … }; /** * 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) { … } device_initcall(ipc_init); static const struct rhashtable_params ipc_kht_params = …; /** * 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) { … } #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 *)) { … } #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) { … } /* * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } bool ipc_rcu_getref(struct kern_ipc_perm *ptr) { … } void ipc_rcu_putref(struct kern_ipc_perm *ptr, void (*func)(struct rcu_head *head)) { … } /** * 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) { … } /* * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } #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 pid_namespace *ipc_seq_pid_ns(struct seq_file *s) { … } /** * 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) { … } static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *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) { … } static void sysvipc_proc_stop(struct seq_file *s, void *it) { … } static int sysvipc_proc_show(struct seq_file *s, void *it) { … } static const struct seq_operations sysvipc_proc_seqops = …; static int sysvipc_proc_open(struct inode *inode, struct file *file) { … } static int sysvipc_proc_release(struct inode *inode, struct file *file) { … } static const struct proc_ops sysvipc_proc_ops = …; #endif /* CONFIG_PROC_FS */
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