/* * 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> */ #include <linux/config.h> #include <linux/mm.h> #include <linux/shm.h> #include <linux/init.h> #include <linux/msg.h> #include <linux/smp_lock.h> #include <linux/vmalloc.h> #include <linux/slab.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 <asm/unistd.h> #include "util.h" struct ipc_proc_iface { const char *path; const char *header; struct ipc_ids *ids; int (*show)(struct seq_file *, void *); }; /** * ipc_init - initialise IPC subsystem * * The various system5 IPC resources (semaphores, messages and shared * memory are initialised */ static int __init ipc_init(void) { sem_init(); msg_init(); shm_init(); return 0; } __initcall(ipc_init); /** * ipc_init_ids - initialise IPC identifiers * @ids: Identifier set * @size: Number of identifiers * * Given a size for the ipc identifier range (limited below IPCMNI) * set up the sequence range to use then allocate and initialise the * array itself. */ void __init ipc_init_ids(struct ipc_ids* ids, int size) { int i; sema_init(&ids->sem,1); if(size > IPCMNI) size = IPCMNI; ids->in_use = 0; ids->max_id = -1; ids->seq = 0; { int seq_limit = INT_MAX/SEQ_MULTIPLIER; if(seq_limit > USHRT_MAX) ids->seq_max = USHRT_MAX; else ids->seq_max = seq_limit; } ids->entries = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*size + sizeof(struct ipc_id_ary)); if(ids->entries == NULL) { printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n"); size = 0; ids->entries = &ids->nullentry; } ids->entries->size = size; for(i=0;i<size;i++) ids->entries->p[i] = NULL; } #ifdef CONFIG_PROC_FS static 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, struct ipc_ids *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 = create_proc_entry(path, S_IRUGO, /* world readable */ NULL /* parent dir */); if (pde) { pde->data = iface; pde->proc_fops = &sysvipc_proc_fops; } else { kfree(iface); } } #endif /** * ipc_findkey - find a key in an ipc identifier set * @ids: Identifier set * @key: The key to find * * Requires ipc_ids.sem locked. * Returns the identifier if found or -1 if not. */ int ipc_findkey(struct ipc_ids* ids, key_t key) { int id; struct kern_ipc_perm* p; int max_id = ids->max_id; /* * rcu_dereference() is not needed here * since ipc_ids.sem is held */ for (id = 0; id <= max_id; id++) { p = ids->entries->p[id]; if(p==NULL) continue; if (key == p->key) return id; } return -1; } /* * Requires ipc_ids.sem locked */ static int grow_ary(struct ipc_ids* ids, int newsize) { struct ipc_id_ary* new; struct ipc_id_ary* old; int i; int size = ids->entries->size; if(newsize > IPCMNI) newsize = IPCMNI; if(newsize <= size) return newsize; new = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*newsize + sizeof(struct ipc_id_ary)); if(new == NULL) return size; new->size = newsize; memcpy(new->p, ids->entries->p, sizeof(struct kern_ipc_perm *)*size + sizeof(struct ipc_id_ary)); for(i=size;i<newsize;i++) { new->p[i] = NULL; } old = ids->entries; /* * Use rcu_assign_pointer() to make sure the memcpyed contents * of the new array are visible before the new array becomes visible. */ rcu_assign_pointer(ids->entries, new); ipc_rcu_putref(old); return newsize; } /** * ipc_addid - add an IPC identifier * @ids: IPC identifier set * @new: new IPC permission set * @size: new size limit for the id array * * Add an entry 'new' to the IPC arrays. The permissions object is * initialised and the first free entry is set up and the id assigned * is returned. The list is returned in a locked state on success. * On failure the list is not locked and -1 is returned. * * Called with ipc_ids.sem held. */ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size) { int id; size = grow_ary(ids,size); /* * rcu_dereference()() is not needed here since * ipc_ids.sem is held */ for (id = 0; id < size; id++) { if(ids->entries->p[id] == NULL) goto found; } return -1; found: ids->in_use++; if (id > ids->max_id) ids->max_id = id; new->cuid = new->uid = current->euid; new->gid = new->cgid = current->egid; new->seq = ids->seq++; if(ids->seq > ids->seq_max) ids->seq = 0; spin_lock_init(&new->lock); new->deleted = 0; rcu_read_lock(); spin_lock(&new->lock); ids->entries->p[id] = new; return id; } /** * ipc_rmid - remove an IPC identifier * @ids: identifier set * @id: Identifier to remove * * The identifier must be valid, and in use. The kernel will panic if * fed an invalid identifier. The entry is removed and internal * variables recomputed. The object associated with the identifier * is returned. * ipc_ids.sem and the spinlock for this ID is hold before this function * is called, and remain locked on the exit. */ struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id) { struct kern_ipc_perm* p; int lid = id % SEQ_MULTIPLIER; if(lid >= ids->entries->size) BUG(); /* * do not need a rcu_dereference()() here to force ordering * on Alpha, since the ipc_ids.sem is held. */ p = ids->entries->p[lid]; ids->entries->p[lid] = NULL; if(p==NULL) BUG(); ids->in_use--; if (lid == ids->max_id) { do { lid--; if(lid == -1) break; } while (ids->entries->p[lid] == NULL); ids->max_id = lid; } p->deleted = 1; return p; } /** * ipc_alloc - allocate ipc space * @size: size desired * * Allocate memory from the appropriate pools and return a pointer to it. * NULL is returned if the allocation fails */ void* ipc_alloc(int size) { void* out; if(size > PAGE_SIZE) out = vmalloc(size); else out = kmalloc(size, GFP_KERNEL); return out; } /** * ipc_free - free ipc space * @ptr: pointer returned by ipc_alloc * @size: size of block * * Free a block created with ipc_alloc. The caller must know the size * used in the allocation call. */ void ipc_free(void* ptr, int size) { if(size > PAGE_SIZE) vfree(ptr); else kfree(ptr); } /* * rcu allocations: * There are three headers that are prepended to the actual allocation: * - during use: ipc_rcu_hdr. * - during the rcu grace period: ipc_rcu_grace. * - [only if vmalloc]: ipc_rcu_sched. * Their lifetime doesn't overlap, thus the headers share the same memory. * Unlike a normal union, they are right-aligned, thus some container_of * forward/backward casting is necessary: */ struct ipc_rcu_hdr { int refcount; int is_vmalloc; void *data[0]; }; struct ipc_rcu_grace { struct rcu_head rcu; /* "void *" makes sure alignment of following data is sane. */ void *data[0]; }; struct ipc_rcu_sched { struct work_struct work; /* "void *" makes sure alignment of following data is sane. */ void *data[0]; }; #define HDRLEN_KMALLOC (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \ sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr)) #define HDRLEN_VMALLOC (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \ sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC) static inline int rcu_use_vmalloc(int size) { /* Too big for a single page? */ if (HDRLEN_KMALLOC + size > PAGE_SIZE) return 1; return 0; } /** * ipc_rcu_alloc - allocate ipc and rcu space * @size: size desired * * Allocate memory for the rcu header structure + the object. * Returns the pointer to the object. * NULL is returned if the allocation fails. */ void* ipc_rcu_alloc(int size) { void* out; /* * We prepend the allocation with the rcu struct, and * workqueue if necessary (for vmalloc). */ if (rcu_use_vmalloc(size)) { out = vmalloc(HDRLEN_VMALLOC + size); if (out) { out += HDRLEN_VMALLOC; container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1; container_of(out, struct ipc_rcu_hdr, data)->refcount = 1; } } else { out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL); if (out) { out += HDRLEN_KMALLOC; container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0; container_of(out, struct ipc_rcu_hdr, data)->refcount = 1; } } return out; } void ipc_rcu_getref(void *ptr) { container_of(ptr, struct ipc_rcu_hdr, data)->refcount++; } /** * ipc_schedule_free - free ipc + rcu space * @head: RCU callback structure for queued work * * Since RCU callback function is called in bh, * we need to defer the vfree to schedule_work */ static void ipc_schedule_free(struct rcu_head *head) { struct ipc_rcu_grace *grace = container_of(head, struct ipc_rcu_grace, rcu); struct ipc_rcu_sched *sched = container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]); INIT_WORK(&sched->work, vfree, sched); schedule_work(&sched->work); } /** * ipc_immediate_free - free ipc + rcu space * @head: RCU callback structure that contains pointer to be freed * * Free from the RCU callback context */ static void ipc_immediate_free(struct rcu_head *head) { struct ipc_rcu_grace *free = container_of(head, struct ipc_rcu_grace, rcu); kfree(free); } void ipc_rcu_putref(void *ptr) { if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0) return; if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) { call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu, ipc_schedule_free); } else { call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu, ipc_immediate_free); } } /** * ipcperms - check IPC permissions * @ipcp: IPC permission set * @flag: desired permission set. * * Check user, group, other permissions for access * to ipc resources. return 0 if allowed */ int ipcperms (struct kern_ipc_perm *ipcp, short flag) { /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */ int requested_mode, granted_mode; requested_mode = (flag >> 6) | (flag >> 3) | flag; granted_mode = ipcp->mode; if (current->euid == ipcp->cuid || current->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) && !capable(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 = in->uid; out->gid = in->gid; out->cuid = in->cuid; out->cgid = in->cgid; out->mode = in->mode; out->seq = in->seq; } /** * ipc64_perm_to_ipc_perm - convert old ipc permissions to new * @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; } /* * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get() * is called with shm_ids.sem locked. Since grow_ary() is also called with * shm_ids.sem down(for Shared Memory), there is no need to add read * barriers here to gurantee the writes in grow_ary() are seen in order * here (for Alpha). * * However ipc_get() itself does not necessary require ipc_ids.sem down. So * if in the future ipc_get() is used by other places without ipc_ids.sem * down, then ipc_get() needs read memery barriers as ipc_lock() does. */ struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id) { struct kern_ipc_perm* out; int lid = id % SEQ_MULTIPLIER; if(lid >= ids->entries->size) return NULL; out = ids->entries->p[lid]; return out; } struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id) { struct kern_ipc_perm* out; int lid = id % SEQ_MULTIPLIER; struct ipc_id_ary* entries; rcu_read_lock(); entries = rcu_dereference(ids->entries); if(lid >= entries->size) { rcu_read_unlock(); return NULL; } out = entries->p[lid]; if(out == NULL) { rcu_read_unlock(); return NULL; } 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 */ if (out->deleted) { spin_unlock(&out->lock); rcu_read_unlock(); return NULL; } return out; } void ipc_lock_by_ptr(struct kern_ipc_perm *perm) { rcu_read_lock(); spin_lock(&perm->lock); } void ipc_unlock(struct kern_ipc_perm* perm) { spin_unlock(&perm->lock); rcu_read_unlock(); } int ipc_buildid(struct ipc_ids* ids, int id, int seq) { return SEQ_MULTIPLIER*seq + id; } int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid) { if(uid/SEQ_MULTIPLIER != ipcp->seq) return 1; return 0; } #ifdef __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 /* __ARCH_WANT_IPC_PARSE_VERSION */ #ifdef CONFIG_PROC_FS static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos) { struct ipc_proc_iface *iface = s->private; struct kern_ipc_perm *ipc = it; loff_t p; /* If we had an ipc id locked before, unlock it */ if (ipc && ipc != SEQ_START_TOKEN) ipc_unlock(ipc); /* * p = *pos - 1 (because id 0 starts at position 1) * + 1 (because we increment the position by one) */ for (p = *pos; p <= iface->ids->max_id; p++) { if ((ipc = ipc_lock(iface->ids, p)) != NULL) { *pos = p + 1; return ipc; } } /* Out of range - return NULL to terminate iteration */ return NULL; } /* * File positions: pos 0 -> header, pos n -> ipc id + 1. * SeqFile iterator: iterator value locked shp or SEQ_TOKEN_START. */ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos) { struct ipc_proc_iface *iface = s->private; struct kern_ipc_perm *ipc; loff_t p; /* * Take the lock - this will be released by the corresponding * call to stop(). */ down(&iface->ids->sem); /* 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 */ for (p = *pos - 1; p <= iface->ids->max_id; p++) { if ((ipc = ipc_lock(iface->ids, p)) != NULL) { *pos = p + 1; return ipc; } } return NULL; } static void sysvipc_proc_stop(struct seq_file *s, void *it) { struct kern_ipc_perm *ipc = it; struct ipc_proc_iface *iface = s->private; /* If we had a locked segment, release it */ if (ipc && ipc != SEQ_START_TOKEN) ipc_unlock(ipc); /* Release the lock we took in start() */ up(&iface->ids->sem); } static int sysvipc_proc_show(struct seq_file *s, void *it) { struct ipc_proc_iface *iface = s->private; if (it == SEQ_START_TOKEN) return seq_puts(s, iface->header); return iface->show(s, it); } static 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) { int ret; struct seq_file *seq; ret = seq_open(file, &sysvipc_proc_seqops); if (!ret) { seq = file->private_data; seq->private = PDE(inode)->data; } return ret; } static struct file_operations sysvipc_proc_fops = { .open = sysvipc_proc_open, .read = seq_read, .llseek = seq_lseek, .release = seq_release, }; #endif /* CONFIG_PROC_FS */