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>
27 #include <linux/vs_base.h>
29 #include <asm/unistd.h>
34 * ipc_init - initialise IPC subsystem
36 * The various system5 IPC resources (semaphores, messages and shared
37 * memory are initialised
40 static int __init ipc_init(void)
50 * ipc_init_ids - initialise IPC identifiers
51 * @ids: Identifier set
52 * @size: Number of identifiers
54 * Given a size for the ipc identifier range (limited below IPCMNI)
55 * set up the sequence range to use then allocate and initialise the
59 void __init ipc_init_ids(struct ipc_ids* ids, int size)
62 sema_init(&ids->sem,1);
71 int seq_limit = INT_MAX/SEQ_MULTIPLIER;
72 if(seq_limit > USHRT_MAX)
73 ids->seq_max = USHRT_MAX;
75 ids->seq_max = seq_limit;
78 ids->entries = ipc_rcu_alloc(sizeof(struct ipc_id)*size);
80 if(ids->entries == NULL) {
81 printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
84 for(i=0;i<ids->size;i++)
85 ids->entries[i].p = NULL;
89 * ipc_findkey - find a key in an ipc identifier set
90 * @ids: Identifier set
91 * @key: The key to find
93 * Requires ipc_ids.sem locked.
94 * Returns the identifier if found or -1 if not.
97 int ipc_findkey(struct ipc_ids* ids, key_t key)
100 struct kern_ipc_perm* p;
101 int max_id = ids->max_id;
104 * read_barrier_depends is not needed here
105 * since ipc_ids.sem is held
107 for (id = 0; id <= max_id; id++) {
108 p = ids->entries[id].p;
111 if (!vx_check(p->xid, VX_IDENT))
120 * Requires ipc_ids.sem locked
122 static int grow_ary(struct ipc_ids* ids, int newsize)
130 if(newsize <= ids->size)
133 new = ipc_rcu_alloc(sizeof(struct ipc_id)*newsize);
136 memcpy(new, ids->entries, sizeof(struct ipc_id)*ids->size);
137 for(i=ids->size;i<newsize;i++) {
144 * before setting the ids->entries to the new array, there must be a
145 * smp_wmb() to make sure the memcpyed contents of the new array are
146 * visible before the new array becomes visible.
148 smp_wmb(); /* prevent seeing new array uninitialized. */
150 smp_wmb(); /* prevent indexing into old array based on new size. */
153 ipc_rcu_free(old, sizeof(struct ipc_id)*i);
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 * read_barrier_depends() is not needed here since
179 * ipc_ids.sem is held
181 for (id = 0; id < size; id++) {
182 if(ids->entries[id].p == 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 new->lock = SPIN_LOCK_UNLOCKED;
201 spin_lock(&new->lock);
202 ids->entries[id].p = 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;
227 * do not need a read_barrier_depends() here to force ordering
228 * on Alpha, since the ipc_ids.sem is held.
230 p = ids->entries[lid].p;
231 ids->entries[lid].p = NULL;
236 if (lid == ids->max_id) {
241 } while (ids->entries[lid].p == 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)
283 struct ipc_rcu_kmalloc
286 /* "void *" makes sure alignment of following data is sane. */
290 struct ipc_rcu_vmalloc
293 struct work_struct work;
294 /* "void *" makes sure alignment of following data is sane. */
298 static inline int rcu_use_vmalloc(int size)
300 /* Too big for a single page? */
301 if (sizeof(struct ipc_rcu_kmalloc) + size > PAGE_SIZE)
307 * ipc_rcu_alloc - allocate ipc and rcu space
308 * @size: size desired
310 * Allocate memory for the rcu header structure + the object.
311 * Returns the pointer to the object.
312 * NULL is returned if the allocation fails.
315 void* ipc_rcu_alloc(int size)
319 * We prepend the allocation with the rcu struct, and
320 * workqueue if necessary (for vmalloc).
322 if (rcu_use_vmalloc(size)) {
323 out = vmalloc(sizeof(struct ipc_rcu_vmalloc) + size);
324 if (out) out += sizeof(struct ipc_rcu_vmalloc);
326 out = kmalloc(sizeof(struct ipc_rcu_kmalloc)+size, GFP_KERNEL);
327 if (out) out += sizeof(struct ipc_rcu_kmalloc);
334 * ipc_schedule_free - free ipc + rcu space
336 * Since RCU callback function is called in bh,
337 * we need to defer the vfree to schedule_work
339 static void ipc_schedule_free(void* arg)
341 struct ipc_rcu_vmalloc *free = arg;
343 INIT_WORK(&free->work, vfree, free);
344 schedule_work(&free->work);
347 void ipc_rcu_free(void* ptr, int size)
349 if (rcu_use_vmalloc(size)) {
350 struct ipc_rcu_vmalloc *free;
351 free = ptr - sizeof(*free);
352 call_rcu(&free->rcu, ipc_schedule_free, free);
354 struct ipc_rcu_kmalloc *free;
355 free = ptr - sizeof(*free);
356 /* kfree takes a "const void *" so gcc warns. So we cast. */
357 call_rcu(&free->rcu, (void (*)(void *))kfree, free);
363 * ipcperms - check IPC permissions
364 * @ipcp: IPC permission set
365 * @flag: desired permission set.
367 * Check user, group, other permissions for access
368 * to ipc resources. return 0 if allowed
371 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
372 { /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
373 int requested_mode, granted_mode;
375 if (!vx_check(ipcp->xid, VX_ADMIN|VX_IDENT)) /* maybe just VX_IDENT? */
377 requested_mode = (flag >> 6) | (flag >> 3) | flag;
378 granted_mode = ipcp->mode;
379 if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
381 else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
383 /* is there some bit set in requested_mode but not in granted_mode? */
384 if ((requested_mode & ~granted_mode & 0007) &&
385 !capable(CAP_IPC_OWNER))
388 return security_ipc_permission(ipcp, flag);
392 * Functions to convert between the kern_ipc_perm structure and the
393 * old/new ipc_perm structures
397 * kernel_to_ipc64_perm - convert kernel ipc permissions to user
398 * @in: kernel permissions
399 * @out: new style IPC permissions
401 * Turn the kernel object 'in' into a set of permissions descriptions
402 * for returning to userspace (out).
406 void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
411 out->cuid = in->cuid;
412 out->cgid = in->cgid;
413 out->mode = in->mode;
418 * ipc64_perm_to_ipc_perm - convert old ipc permissions to new
419 * @in: new style IPC permissions
420 * @out: old style IPC permissions
422 * Turn the new style permissions object in into a compatibility
423 * object and store it into the 'out' pointer.
426 void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
429 SET_UID(out->uid, in->uid);
430 SET_GID(out->gid, in->gid);
431 SET_UID(out->cuid, in->cuid);
432 SET_GID(out->cgid, in->cgid);
433 out->mode = in->mode;
438 * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get()
439 * is called with shm_ids.sem locked. Since grow_ary() is also called with
440 * shm_ids.sem down(for Shared Memory), there is no need to add read
441 * barriers here to gurantee the writes in grow_ary() are seen in order
444 * However ipc_get() itself does not necessary require ipc_ids.sem down. So
445 * if in the future ipc_get() is used by other places without ipc_ids.sem
446 * down, then ipc_get() needs read memery barriers as ipc_lock() does.
448 struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
450 struct kern_ipc_perm* out;
451 int lid = id % SEQ_MULTIPLIER;
454 out = ids->entries[lid].p;
458 struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
460 struct kern_ipc_perm* out;
461 int lid = id % SEQ_MULTIPLIER;
462 struct ipc_id* entries;
465 if(lid >= ids->size) {
471 * Note: The following two read barriers are corresponding
472 * to the two write barriers in grow_ary(). They guarantee
473 * the writes are seen in the same order on the read side.
474 * smp_rmb() has effect on all CPUs. read_barrier_depends()
475 * is used if there are data dependency between two reads, and
476 * has effect only on Alpha.
478 smp_rmb(); /* prevent indexing old array with new size */
479 entries = ids->entries;
480 read_barrier_depends(); /*prevent seeing new array unitialized */
481 out = entries[lid].p;
486 spin_lock(&out->lock);
488 /* ipc_rmid() may have already freed the ID while ipc_lock
489 * was spinning: here verify that the structure is still valid
492 spin_unlock(&out->lock);
499 void ipc_unlock(struct kern_ipc_perm* perm)
501 spin_unlock(&perm->lock);
505 int ipc_buildid(struct ipc_ids* ids, int id, int seq)
507 return SEQ_MULTIPLIER*seq + id;
510 int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid)
512 if(uid/SEQ_MULTIPLIER != ipcp->seq)
517 #ifdef __ARCH_WANT_IPC_PARSE_VERSION
521 * ipc_parse_version - IPC call version
522 * @cmd: pointer to command
524 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
525 * The cmd value is turned from an encoding command and version into
526 * just the command code.
529 int ipc_parse_version (int *cmd)
539 #endif /* __ARCH_WANT_IPC_PARSE_VERSION */