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/*
* 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 <manfreds@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/highuid.h>
#include <linux/security.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>
#include <asm/unistd.h>
#include "util.h"
/**
* 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;
}
/**
* 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
*
* 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
*
* 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 */
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