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>
28 #include <asm/unistd.h>
33 * ipc_init - initialise IPC subsystem
35 * The various system5 IPC resources (semaphores, messages and shared
36 * memory are initialised
39 static int __init ipc_init(void)
49 * ipc_init_ids - initialise IPC identifiers
50 * @ids: Identifier set
51 * @size: Number of identifiers
53 * Given a size for the ipc identifier range (limited below IPCMNI)
54 * set up the sequence range to use then allocate and initialise the
58 void __init ipc_init_ids(struct ipc_ids* ids, int size)
61 sema_init(&ids->sem,1);
69 int seq_limit = INT_MAX/SEQ_MULTIPLIER;
70 if(seq_limit > USHRT_MAX)
71 ids->seq_max = USHRT_MAX;
73 ids->seq_max = seq_limit;
76 ids->entries = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*size +
77 sizeof(struct ipc_id_ary));
79 if(ids->entries == NULL) {
80 printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
82 ids->entries = &ids->nullentry;
84 ids->entries->size = size;
86 ids->entries->p[i] = NULL;
90 * ipc_findkey - find a key in an ipc identifier set
91 * @ids: Identifier set
92 * @key: The key to find
94 * Requires ipc_ids.sem locked.
95 * Returns the identifier if found or -1 if not.
98 int ipc_findkey(struct ipc_ids* ids, key_t key)
101 struct kern_ipc_perm* p;
102 int max_id = ids->max_id;
105 * rcu_dereference() is not needed here
106 * since ipc_ids.sem is held
108 for (id = 0; id <= max_id; id++) {
109 p = ids->entries->p[id];
112 if (!vx_check(p->xid, VX_IDENT))
121 * Requires ipc_ids.sem locked
123 static int grow_ary(struct ipc_ids* ids, int newsize)
125 struct ipc_id_ary* new;
126 struct ipc_id_ary* old;
128 int size = ids->entries->size;
135 new = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*newsize +
136 sizeof(struct ipc_id_ary));
140 memcpy(new->p, ids->entries->p, sizeof(struct kern_ipc_perm *)*size +
141 sizeof(struct ipc_id_ary));
142 for(i=size;i<newsize;i++) {
148 * Use rcu_assign_pointer() to make sure the memcpyed contents
149 * of the new array are visible before the new array becomes visible.
151 rcu_assign_pointer(ids->entries, new);
158 * ipc_addid - add an IPC identifier
159 * @ids: IPC identifier set
160 * @new: new IPC permission set
161 * @size: new size limit for the id array
163 * Add an entry 'new' to the IPC arrays. The permissions object is
164 * initialised and the first free entry is set up and the id assigned
165 * is returned. The list is returned in a locked state on success.
166 * On failure the list is not locked and -1 is returned.
168 * Called with ipc_ids.sem held.
171 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
175 size = grow_ary(ids,size);
178 * rcu_dereference()() is not needed here since
179 * ipc_ids.sem is held
181 for (id = 0; id < size; id++) {
182 if(ids->entries->p[id] == NULL)
188 if (id > ids->max_id)
191 new->cuid = new->uid = current->euid;
192 new->gid = new->cgid = current->egid;
194 new->seq = ids->seq++;
195 if(ids->seq > ids->seq_max)
198 spin_lock_init(&new->lock);
201 spin_lock(&new->lock);
202 ids->entries->p[id] = new;
207 * ipc_rmid - remove an IPC identifier
208 * @ids: identifier set
209 * @id: Identifier to remove
211 * The identifier must be valid, and in use. The kernel will panic if
212 * fed an invalid identifier. The entry is removed and internal
213 * variables recomputed. The object associated with the identifier
215 * ipc_ids.sem and the spinlock for this ID is hold before this function
216 * is called, and remain locked on the exit.
219 struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id)
221 struct kern_ipc_perm* p;
222 int lid = id % SEQ_MULTIPLIER;
223 if(lid >= ids->entries->size)
227 * do not need a rcu_dereference()() here to force ordering
228 * on Alpha, since the ipc_ids.sem is held.
230 p = ids->entries->p[lid];
231 ids->entries->p[lid] = NULL;
236 if (lid == ids->max_id) {
241 } while (ids->entries->p[lid] == NULL);
249 * ipc_alloc - allocate ipc space
250 * @size: size desired
252 * Allocate memory from the appropriate pools and return a pointer to it.
253 * NULL is returned if the allocation fails
256 void* ipc_alloc(int size)
262 out = kmalloc(size, GFP_KERNEL);
267 * ipc_free - free ipc space
268 * @ptr: pointer returned by ipc_alloc
269 * @size: size of block
271 * Free a block created with ipc_alloc. The caller must know the size
272 * used in the allocation call.
275 void ipc_free(void* ptr, int size)
285 * There are three headers that are prepended to the actual allocation:
286 * - during use: ipc_rcu_hdr.
287 * - during the rcu grace period: ipc_rcu_grace.
288 * - [only if vmalloc]: ipc_rcu_sched.
289 * Their lifetime doesn't overlap, thus the headers share the same memory.
290 * Unlike a normal union, they are right-aligned, thus some container_of
291 * forward/backward casting is necessary:
304 /* "void *" makes sure alignment of following data is sane. */
310 struct work_struct work;
311 /* "void *" makes sure alignment of following data is sane. */
315 #define HDRLEN_KMALLOC (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
316 sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
317 #define HDRLEN_VMALLOC (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
318 sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
320 static inline int rcu_use_vmalloc(int size)
322 /* Too big for a single page? */
323 if (HDRLEN_KMALLOC + size > PAGE_SIZE)
329 * ipc_rcu_alloc - allocate ipc and rcu space
330 * @size: size desired
332 * Allocate memory for the rcu header structure + the object.
333 * Returns the pointer to the object.
334 * NULL is returned if the allocation fails.
337 void* ipc_rcu_alloc(int size)
341 * We prepend the allocation with the rcu struct, and
342 * workqueue if necessary (for vmalloc).
344 if (rcu_use_vmalloc(size)) {
345 out = vmalloc(HDRLEN_VMALLOC + size);
347 out += HDRLEN_VMALLOC;
348 container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
349 container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
352 out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
354 out += HDRLEN_KMALLOC;
355 container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
356 container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
363 void ipc_rcu_getref(void *ptr)
365 container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
369 * ipc_schedule_free - free ipc + rcu space
371 * Since RCU callback function is called in bh,
372 * we need to defer the vfree to schedule_work
374 static void ipc_schedule_free(struct rcu_head *head)
376 struct ipc_rcu_grace *grace =
377 container_of(head, struct ipc_rcu_grace, rcu);
378 struct ipc_rcu_sched *sched =
379 container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]);
381 INIT_WORK(&sched->work, vfree, sched);
382 schedule_work(&sched->work);
386 * ipc_immediate_free - free ipc + rcu space
388 * Free from the RCU callback context
391 static void ipc_immediate_free(struct rcu_head *head)
393 struct ipc_rcu_grace *free =
394 container_of(head, struct ipc_rcu_grace, rcu);
398 void ipc_rcu_putref(void *ptr)
400 if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
403 if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
404 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
407 call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
413 * ipcperms - check IPC permissions
414 * @ipcp: IPC permission set
415 * @flag: desired permission set.
417 * Check user, group, other permissions for access
418 * to ipc resources. return 0 if allowed
421 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
422 { /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
423 int requested_mode, granted_mode;
425 if (!vx_check(ipcp->xid, VX_ADMIN|VX_IDENT)) /* maybe just VX_IDENT? */
427 requested_mode = (flag >> 6) | (flag >> 3) | flag;
428 granted_mode = ipcp->mode;
429 if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
431 else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
433 /* is there some bit set in requested_mode but not in granted_mode? */
434 if ((requested_mode & ~granted_mode & 0007) &&
435 !capable(CAP_IPC_OWNER))
438 return security_ipc_permission(ipcp, flag);
442 * Functions to convert between the kern_ipc_perm structure and the
443 * old/new ipc_perm structures
447 * kernel_to_ipc64_perm - convert kernel ipc permissions to user
448 * @in: kernel permissions
449 * @out: new style IPC permissions
451 * Turn the kernel object 'in' into a set of permissions descriptions
452 * for returning to userspace (out).
456 void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
461 out->cuid = in->cuid;
462 out->cgid = in->cgid;
463 out->mode = in->mode;
468 * ipc64_perm_to_ipc_perm - convert old ipc permissions to new
469 * @in: new style IPC permissions
470 * @out: old style IPC permissions
472 * Turn the new style permissions object in into a compatibility
473 * object and store it into the 'out' pointer.
476 void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
479 SET_UID(out->uid, in->uid);
480 SET_GID(out->gid, in->gid);
481 SET_UID(out->cuid, in->cuid);
482 SET_GID(out->cgid, in->cgid);
483 out->mode = in->mode;
488 * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get()
489 * is called with shm_ids.sem locked. Since grow_ary() is also called with
490 * shm_ids.sem down(for Shared Memory), there is no need to add read
491 * barriers here to gurantee the writes in grow_ary() are seen in order
494 * However ipc_get() itself does not necessary require ipc_ids.sem down. So
495 * if in the future ipc_get() is used by other places without ipc_ids.sem
496 * down, then ipc_get() needs read memery barriers as ipc_lock() does.
498 struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
500 struct kern_ipc_perm* out;
501 int lid = id % SEQ_MULTIPLIER;
502 if(lid >= ids->entries->size)
504 out = ids->entries->p[lid];
508 struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
510 struct kern_ipc_perm* out;
511 int lid = id % SEQ_MULTIPLIER;
512 struct ipc_id_ary* entries;
515 entries = rcu_dereference(ids->entries);
516 if(lid >= entries->size) {
520 out = entries->p[lid];
525 spin_lock(&out->lock);
527 /* ipc_rmid() may have already freed the ID while ipc_lock
528 * was spinning: here verify that the structure is still valid
531 spin_unlock(&out->lock);
538 void ipc_lock_by_ptr(struct kern_ipc_perm *perm)
541 spin_lock(&perm->lock);
544 void ipc_unlock(struct kern_ipc_perm* perm)
546 spin_unlock(&perm->lock);
550 int ipc_buildid(struct ipc_ids* ids, int id, int seq)
552 return SEQ_MULTIPLIER*seq + id;
555 int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid)
557 if(uid/SEQ_MULTIPLIER != ipcp->seq)
562 #ifdef __ARCH_WANT_IPC_PARSE_VERSION
566 * ipc_parse_version - IPC call version
567 * @cmd: pointer to command
569 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
570 * The cmd value is turned from an encoding command and version into
571 * just the command code.
574 int ipc_parse_version (int *cmd)
584 #endif /* __ARCH_WANT_IPC_PARSE_VERSION */