3 * Copyright (C) 1992 Krishna Balasubramanian
5 * Sep 1997 - Call suser() last after "normal" permission checks so we
6 * get BSD style process accounting right.
7 * Occurs in several places in the IPC code.
8 * Chris Evans, <chris@ferret.lmh.ox.ac.uk>
9 * Nov 1999 - ipc helper functions, unified SMP locking
10 * Manfred Spraul <manfreds@colorfullife.com>
11 * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
12 * Mingming Cao <cmm@us.ibm.com>
15 #include <linux/config.h>
17 #include <linux/shm.h>
18 #include <linux/init.h>
19 #include <linux/msg.h>
20 #include <linux/smp_lock.h>
21 #include <linux/vmalloc.h>
22 #include <linux/slab.h>
23 #include <linux/highuid.h>
24 #include <linux/security.h>
25 #include <linux/rcupdate.h>
26 #include <linux/workqueue.h>
31 * ipc_init - initialise IPC subsystem
33 * The various system5 IPC resources (semaphores, messages and shared
34 * memory are initialised
37 static int __init ipc_init(void)
47 * ipc_init_ids - initialise IPC identifiers
48 * @ids: Identifier set
49 * @size: Number of identifiers
51 * Given a size for the ipc identifier range (limited below IPCMNI)
52 * set up the sequence range to use then allocate and initialise the
56 void __init ipc_init_ids(struct ipc_ids* ids, int size)
59 sema_init(&ids->sem,1);
68 int seq_limit = INT_MAX/SEQ_MULTIPLIER;
69 if(seq_limit > USHRT_MAX)
70 ids->seq_max = USHRT_MAX;
72 ids->seq_max = seq_limit;
75 ids->entries = ipc_rcu_alloc(sizeof(struct ipc_id)*size);
77 if(ids->entries == NULL) {
78 printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
81 for(i=0;i<ids->size;i++)
82 ids->entries[i].p = NULL;
86 * ipc_findkey - find a key in an ipc identifier set
87 * @ids: Identifier set
88 * @key: The key to find
90 * Requires ipc_ids.sem locked.
91 * Returns the identifier if found or -1 if not.
94 int ipc_findkey(struct ipc_ids* ids, key_t key)
97 struct kern_ipc_perm* p;
98 int max_id = ids->max_id;
101 * read_barrier_depends is not needed here
102 * since ipc_ids.sem is held
104 for (id = 0; id <= max_id; id++) {
105 p = ids->entries[id].p;
115 * Requires ipc_ids.sem locked
117 static int grow_ary(struct ipc_ids* ids, int newsize)
125 if(newsize <= ids->size)
128 new = ipc_rcu_alloc(sizeof(struct ipc_id)*newsize);
131 memcpy(new, ids->entries, sizeof(struct ipc_id)*ids->size);
132 for(i=ids->size;i<newsize;i++) {
139 * before setting the ids->entries to the new array, there must be a
140 * smp_wmb() to make sure the memcpyed contents of the new array are
141 * visible before the new array becomes visible.
143 smp_wmb(); /* prevent seeing new array uninitialized. */
145 smp_wmb(); /* prevent indexing into old array based on new size. */
148 ipc_rcu_free(old, sizeof(struct ipc_id)*i);
153 * ipc_addid - add an IPC identifier
154 * @ids: IPC identifier set
155 * @new: new IPC permission set
156 * @size: new size limit for the id array
158 * Add an entry 'new' to the IPC arrays. The permissions object is
159 * initialised and the first free entry is set up and the id assigned
160 * is returned. The list is returned in a locked state on success.
161 * On failure the list is not locked and -1 is returned.
163 * Called with ipc_ids.sem held.
166 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
170 size = grow_ary(ids,size);
173 * read_barrier_depends() is not needed here since
174 * ipc_ids.sem is held
176 for (id = 0; id < size; id++) {
177 if(ids->entries[id].p == NULL)
183 if (id > ids->max_id)
186 new->cuid = new->uid = current->euid;
187 new->gid = new->cgid = current->egid;
189 new->seq = ids->seq++;
190 if(ids->seq > ids->seq_max)
193 new->lock = SPIN_LOCK_UNLOCKED;
196 spin_lock(&new->lock);
197 ids->entries[id].p = new;
202 * ipc_rmid - remove an IPC identifier
203 * @ids: identifier set
204 * @id: Identifier to remove
206 * The identifier must be valid, and in use. The kernel will panic if
207 * fed an invalid identifier. The entry is removed and internal
208 * variables recomputed. The object associated with the identifier
210 * ipc_ids.sem and the spinlock for this ID is hold before this function
211 * is called, and remain locked on the exit.
214 struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id)
216 struct kern_ipc_perm* p;
217 int lid = id % SEQ_MULTIPLIER;
222 * do not need a read_barrier_depends() here to force ordering
223 * on Alpha, since the ipc_ids.sem is held.
225 p = ids->entries[lid].p;
226 ids->entries[lid].p = NULL;
231 if (lid == ids->max_id) {
236 } while (ids->entries[lid].p == NULL);
244 * ipc_alloc - allocate ipc space
245 * @size: size desired
247 * Allocate memory from the appropriate pools and return a pointer to it.
248 * NULL is returned if the allocation fails
251 void* ipc_alloc(int size)
257 out = kmalloc(size, GFP_KERNEL);
262 * ipc_free - free ipc space
263 * @ptr: pointer returned by ipc_alloc
264 * @size: size of block
266 * Free a block created with ipc_alloc. The caller must know the size
267 * used in the allocation call.
270 void ipc_free(void* ptr, int size)
278 struct ipc_rcu_kmalloc
281 /* "void *" makes sure alignment of following data is sane. */
285 struct ipc_rcu_vmalloc
288 struct work_struct work;
289 /* "void *" makes sure alignment of following data is sane. */
293 static inline int rcu_use_vmalloc(int size)
295 /* Too big for a single page? */
296 if (sizeof(struct ipc_rcu_kmalloc) + size > PAGE_SIZE)
302 * ipc_rcu_alloc - allocate ipc and rcu space
303 * @size: size desired
305 * Allocate memory for the rcu header structure + the object.
306 * Returns the pointer to the object.
307 * NULL is returned if the allocation fails.
310 void* ipc_rcu_alloc(int size)
314 * We prepend the allocation with the rcu struct, and
315 * workqueue if necessary (for vmalloc).
317 if (rcu_use_vmalloc(size)) {
318 out = vmalloc(sizeof(struct ipc_rcu_vmalloc) + size);
319 if (out) out += sizeof(struct ipc_rcu_vmalloc);
321 out = kmalloc(sizeof(struct ipc_rcu_kmalloc)+size, GFP_KERNEL);
322 if (out) out += sizeof(struct ipc_rcu_kmalloc);
329 * ipc_schedule_free - free ipc + rcu space
331 * Since RCU callback function is called in bh,
332 * we need to defer the vfree to schedule_work
334 static void ipc_schedule_free(void* arg)
336 struct ipc_rcu_vmalloc *free = arg;
338 INIT_WORK(&free->work, vfree, free);
339 schedule_work(&free->work);
342 void ipc_rcu_free(void* ptr, int size)
344 if (rcu_use_vmalloc(size)) {
345 struct ipc_rcu_vmalloc *free;
346 free = ptr - sizeof(*free);
347 call_rcu(&free->rcu, ipc_schedule_free, free);
349 struct ipc_rcu_kmalloc *free;
350 free = ptr - sizeof(*free);
351 /* kfree takes a "const void *" so gcc warns. So we cast. */
352 call_rcu(&free->rcu, (void (*)(void *))kfree, free);
358 * ipcperms - check IPC permissions
359 * @ipcp: IPC permission set
360 * @flag: desired permission set.
362 * Check user, group, other permissions for access
363 * to ipc resources. return 0 if allowed
366 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
367 { /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
368 int requested_mode, granted_mode;
370 requested_mode = (flag >> 6) | (flag >> 3) | flag;
371 granted_mode = ipcp->mode;
372 if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
374 else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
376 /* is there some bit set in requested_mode but not in granted_mode? */
377 if ((requested_mode & ~granted_mode & 0007) &&
378 !capable(CAP_IPC_OWNER))
381 return security_ipc_permission(ipcp, flag);
385 * Functions to convert between the kern_ipc_perm structure and the
386 * old/new ipc_perm structures
390 * kernel_to_ipc64_perm - convert kernel ipc permissions to user
391 * @in: kernel permissions
392 * @out: new style IPC permissions
394 * Turn the kernel object 'in' into a set of permissions descriptions
395 * for returning to userspace (out).
399 void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
404 out->cuid = in->cuid;
405 out->cgid = in->cgid;
406 out->mode = in->mode;
411 * ipc64_perm_to_ipc_perm - convert old ipc permissions to new
412 * @in: new style IPC permissions
413 * @out: old style IPC permissions
415 * Turn the new style permissions object in into a compatibility
416 * object and store it into the 'out' pointer.
419 void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
422 SET_UID(out->uid, in->uid);
423 SET_GID(out->gid, in->gid);
424 SET_UID(out->cuid, in->cuid);
425 SET_GID(out->cgid, in->cgid);
426 out->mode = in->mode;
431 * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get()
432 * is called with shm_ids.sem locked. Since grow_ary() is also called with
433 * shm_ids.sem down(for Shared Memory), there is no need to add read
434 * barriers here to gurantee the writes in grow_ary() are seen in order
437 * However ipc_get() itself does not necessary require ipc_ids.sem down. So
438 * if in the future ipc_get() is used by other places without ipc_ids.sem
439 * down, then ipc_get() needs read memery barriers as ipc_lock() does.
441 struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
443 struct kern_ipc_perm* out;
444 int lid = id % SEQ_MULTIPLIER;
447 out = ids->entries[lid].p;
451 struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
453 struct kern_ipc_perm* out;
454 int lid = id % SEQ_MULTIPLIER;
455 struct ipc_id* entries;
458 if(lid >= ids->size) {
464 * Note: The following two read barriers are corresponding
465 * to the two write barriers in grow_ary(). They guarantee
466 * the writes are seen in the same order on the read side.
467 * smp_rmb() has effect on all CPUs. read_barrier_depends()
468 * is used if there are data dependency between two reads, and
469 * has effect only on Alpha.
471 smp_rmb(); /* prevent indexing old array with new size */
472 entries = ids->entries;
473 read_barrier_depends(); /*prevent seeing new array unitialized */
474 out = entries[lid].p;
479 spin_lock(&out->lock);
481 /* ipc_rmid() may have already freed the ID while ipc_lock
482 * was spinning: here verify that the structure is still valid
485 spin_unlock(&out->lock);
492 void ipc_unlock(struct kern_ipc_perm* perm)
494 spin_unlock(&perm->lock);
498 int ipc_buildid(struct ipc_ids* ids, int id, int seq)
500 return SEQ_MULTIPLIER*seq + id;
503 int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid)
505 if(uid/SEQ_MULTIPLIER != ipcp->seq)
510 #if !defined(__ia64__) && !defined(__x86_64__) && !defined(__hppa__)
513 * ipc_parse_version - IPC call version
514 * @cmd: pointer to command
516 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
517 * The cmd value is turned from an encoding command and version into
518 * just the command code.
521 int ipc_parse_version (int *cmd)
531 #endif /* __ia64__ */