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);
70 int seq_limit = INT_MAX/SEQ_MULTIPLIER;
71 if(seq_limit > USHRT_MAX)
72 ids->seq_max = USHRT_MAX;
74 ids->seq_max = seq_limit;
77 ids->entries = ipc_rcu_alloc(sizeof(struct ipc_id)*size);
79 if(ids->entries == NULL) {
80 printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
83 for(i=0;i<ids->size;i++)
84 ids->entries[i].p = NULL;
88 * ipc_findkey - find a key in an ipc identifier set
89 * @ids: Identifier set
90 * @key: The key to find
92 * Requires ipc_ids.sem locked.
93 * Returns the identifier if found or -1 if not.
96 int ipc_findkey(struct ipc_ids* ids, key_t key)
99 struct kern_ipc_perm* p;
100 int max_id = ids->max_id;
103 * read_barrier_depends is not needed here
104 * since ipc_ids.sem is held
106 for (id = 0; id <= max_id; id++) {
107 p = ids->entries[id].p;
110 if (!vx_check(p->xid, VX_IDENT))
119 * Requires ipc_ids.sem locked
121 static int grow_ary(struct ipc_ids* ids, int newsize)
129 if(newsize <= ids->size)
132 new = ipc_rcu_alloc(sizeof(struct ipc_id)*newsize);
135 memcpy(new, ids->entries, sizeof(struct ipc_id)*ids->size);
136 for(i=ids->size;i<newsize;i++) {
143 * before setting the ids->entries to the new array, there must be a
144 * smp_wmb() to make sure the memcpyed contents of the new array are
145 * visible before the new array becomes visible.
147 smp_wmb(); /* prevent seeing new array uninitialized. */
149 smp_wmb(); /* prevent indexing into old array based on new size. */
152 ipc_rcu_free(old, sizeof(struct ipc_id)*i);
157 * ipc_addid - add an IPC identifier
158 * @ids: IPC identifier set
159 * @new: new IPC permission set
160 * @size: new size limit for the id array
162 * Add an entry 'new' to the IPC arrays. The permissions object is
163 * initialised and the first free entry is set up and the id assigned
164 * is returned. The list is returned in a locked state on success.
165 * On failure the list is not locked and -1 is returned.
167 * Called with ipc_ids.sem held.
170 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
174 size = grow_ary(ids,size);
177 * read_barrier_depends() is not needed here since
178 * ipc_ids.sem is held
180 for (id = 0; id < size; id++) {
181 if(ids->entries[id].p == NULL)
187 if (id > ids->max_id)
190 new->cuid = new->uid = current->euid;
191 new->gid = new->cgid = current->egid;
193 new->seq = ids->seq++;
194 if(ids->seq > ids->seq_max)
197 new->lock = SPIN_LOCK_UNLOCKED;
200 spin_lock(&new->lock);
201 ids->entries[id].p = new;
206 * ipc_rmid - remove an IPC identifier
207 * @ids: identifier set
208 * @id: Identifier to remove
210 * The identifier must be valid, and in use. The kernel will panic if
211 * fed an invalid identifier. The entry is removed and internal
212 * variables recomputed. The object associated with the identifier
214 * ipc_ids.sem and the spinlock for this ID is hold before this function
215 * is called, and remain locked on the exit.
218 struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id)
220 struct kern_ipc_perm* p;
221 int lid = id % SEQ_MULTIPLIER;
226 * do not need a read_barrier_depends() here to force ordering
227 * on Alpha, since the ipc_ids.sem is held.
229 p = ids->entries[lid].p;
230 ids->entries[lid].p = NULL;
235 if (lid == ids->max_id) {
240 } while (ids->entries[lid].p == NULL);
248 * ipc_alloc - allocate ipc space
249 * @size: size desired
251 * Allocate memory from the appropriate pools and return a pointer to it.
252 * NULL is returned if the allocation fails
255 void* ipc_alloc(int size)
261 out = kmalloc(size, GFP_KERNEL);
266 * ipc_free - free ipc space
267 * @ptr: pointer returned by ipc_alloc
268 * @size: size of block
270 * Free a block created with ipc_alloc. The caller must know the size
271 * used in the allocation call.
274 void ipc_free(void* ptr, int size)
282 struct ipc_rcu_kmalloc
285 /* "void *" makes sure alignment of following data is sane. */
289 struct ipc_rcu_vmalloc
292 struct work_struct work;
293 /* "void *" makes sure alignment of following data is sane. */
297 static inline int rcu_use_vmalloc(int size)
299 /* Too big for a single page? */
300 if (sizeof(struct ipc_rcu_kmalloc) + size > PAGE_SIZE)
306 * ipc_rcu_alloc - allocate ipc and rcu space
307 * @size: size desired
309 * Allocate memory for the rcu header structure + the object.
310 * Returns the pointer to the object.
311 * NULL is returned if the allocation fails.
314 void* ipc_rcu_alloc(int size)
318 * We prepend the allocation with the rcu struct, and
319 * workqueue if necessary (for vmalloc).
321 if (rcu_use_vmalloc(size)) {
322 out = vmalloc(sizeof(struct ipc_rcu_vmalloc) + size);
323 if (out) out += sizeof(struct ipc_rcu_vmalloc);
325 out = kmalloc(sizeof(struct ipc_rcu_kmalloc)+size, GFP_KERNEL);
326 if (out) out += sizeof(struct ipc_rcu_kmalloc);
333 * ipc_schedule_free - free ipc + rcu space
335 * Since RCU callback function is called in bh,
336 * we need to defer the vfree to schedule_work
338 static void ipc_schedule_free(void* arg)
340 struct ipc_rcu_vmalloc *free = arg;
342 INIT_WORK(&free->work, vfree, free);
343 schedule_work(&free->work);
346 void ipc_rcu_free(void* ptr, int size)
348 if (rcu_use_vmalloc(size)) {
349 struct ipc_rcu_vmalloc *free;
350 free = ptr - sizeof(*free);
351 call_rcu(&free->rcu, ipc_schedule_free, free);
353 struct ipc_rcu_kmalloc *free;
354 free = ptr - sizeof(*free);
355 /* kfree takes a "const void *" so gcc warns. So we cast. */
356 call_rcu(&free->rcu, (void (*)(void *))kfree, free);
362 * ipcperms - check IPC permissions
363 * @ipcp: IPC permission set
364 * @flag: desired permission set.
366 * Check user, group, other permissions for access
367 * to ipc resources. return 0 if allowed
370 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
371 { /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
372 int requested_mode, granted_mode;
374 if (!vx_check(ipcp->xid, VX_ADMIN|VX_IDENT)) /* maybe just VX_IDENT? */
376 requested_mode = (flag >> 6) | (flag >> 3) | flag;
377 granted_mode = ipcp->mode;
378 if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
380 else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
382 /* is there some bit set in requested_mode but not in granted_mode? */
383 if ((requested_mode & ~granted_mode & 0007) &&
384 !capable(CAP_IPC_OWNER))
387 return security_ipc_permission(ipcp, flag);
391 * Functions to convert between the kern_ipc_perm structure and the
392 * old/new ipc_perm structures
396 * kernel_to_ipc64_perm - convert kernel ipc permissions to user
397 * @in: kernel permissions
398 * @out: new style IPC permissions
400 * Turn the kernel object 'in' into a set of permissions descriptions
401 * for returning to userspace (out).
405 void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
410 out->cuid = in->cuid;
411 out->cgid = in->cgid;
412 out->mode = in->mode;
417 * ipc64_perm_to_ipc_perm - convert old ipc permissions to new
418 * @in: new style IPC permissions
419 * @out: old style IPC permissions
421 * Turn the new style permissions object in into a compatibility
422 * object and store it into the 'out' pointer.
425 void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
428 SET_UID(out->uid, in->uid);
429 SET_GID(out->gid, in->gid);
430 SET_UID(out->cuid, in->cuid);
431 SET_GID(out->cgid, in->cgid);
432 out->mode = in->mode;
437 * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get()
438 * is called with shm_ids.sem locked. Since grow_ary() is also called with
439 * shm_ids.sem down(for Shared Memory), there is no need to add read
440 * barriers here to gurantee the writes in grow_ary() are seen in order
443 * However ipc_get() itself does not necessary require ipc_ids.sem down. So
444 * if in the future ipc_get() is used by other places without ipc_ids.sem
445 * down, then ipc_get() needs read memery barriers as ipc_lock() does.
447 struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
449 struct kern_ipc_perm* out;
450 int lid = id % SEQ_MULTIPLIER;
453 out = ids->entries[lid].p;
457 struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
459 struct kern_ipc_perm* out;
460 int lid = id % SEQ_MULTIPLIER;
461 struct ipc_id* entries;
464 if(lid >= ids->size) {
470 * Note: The following two read barriers are corresponding
471 * to the two write barriers in grow_ary(). They guarantee
472 * the writes are seen in the same order on the read side.
473 * smp_rmb() has effect on all CPUs. read_barrier_depends()
474 * is used if there are data dependency between two reads, and
475 * has effect only on Alpha.
477 smp_rmb(); /* prevent indexing old array with new size */
478 entries = ids->entries;
479 read_barrier_depends(); /*prevent seeing new array unitialized */
480 out = entries[lid].p;
485 spin_lock(&out->lock);
487 /* ipc_rmid() may have already freed the ID while ipc_lock
488 * was spinning: here verify that the structure is still valid
491 spin_unlock(&out->lock);
498 void ipc_unlock(struct kern_ipc_perm* perm)
500 spin_unlock(&perm->lock);
504 int ipc_buildid(struct ipc_ids* ids, int id, int seq)
506 return SEQ_MULTIPLIER*seq + id;
509 int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid)
511 if(uid/SEQ_MULTIPLIER != ipcp->seq)
516 #ifdef __ARCH_WANT_IPC_PARSE_VERSION
520 * ipc_parse_version - IPC call version
521 * @cmd: pointer to command
523 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
524 * The cmd value is turned from an encoding command and version into
525 * just the command code.
528 int ipc_parse_version (int *cmd)
538 #endif /* __ARCH_WANT_IPC_PARSE_VERSION */