Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

738 lines (643 sloc) 17.229 kb
/*
* 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 <manfred@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/capability.h>
#include <linux/highuid.h>
#include <linux/security.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <asm/unistd.h>
#include "util.h"
struct ipc_proc_iface {
const char *path;
const char *header;
struct ipc_ids *ids;
int (*show)(struct seq_file *, void *);
};
/**
* 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;
}
#ifdef CONFIG_PROC_FS
static struct file_operations sysvipc_proc_fops;
/**
* ipc_init_proc_interface - Create a proc interface for sysipc types
* using a seq_file interface.
* @path: Path in procfs
* @header: Banner to be printed at the beginning of the file.
* @ids: ipc id table to iterate.
* @show: show routine.
*/
void __init ipc_init_proc_interface(const char *path, const char *header,
struct ipc_ids *ids,
int (*show)(struct seq_file *, void *))
{
struct proc_dir_entry *pde;
struct ipc_proc_iface *iface;
iface = kmalloc(sizeof(*iface), GFP_KERNEL);
if (!iface)
return;
iface->path = path;
iface->header = header;
iface->ids = ids;
iface->show = show;
pde = create_proc_entry(path,
S_IRUGO, /* world readable */
NULL /* parent dir */);
if (pde) {
pde->data = iface;
pde->proc_fops = &sysvipc_proc_fops;
} else {
kfree(iface);
}
}
#endif
/**
* 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);
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
* @head: RCU callback structure for queued work
*
* 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
* @head: RCU callback structure that contains pointer to be freed
*
* 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 */
#ifdef CONFIG_PROC_FS
static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
{
struct ipc_proc_iface *iface = s->private;
struct kern_ipc_perm *ipc = it;
loff_t p;
/* If we had an ipc id locked before, unlock it */
if (ipc && ipc != SEQ_START_TOKEN)
ipc_unlock(ipc);
/*
* p = *pos - 1 (because id 0 starts at position 1)
* + 1 (because we increment the position by one)
*/
for (p = *pos; p <= iface->ids->max_id; p++) {
if ((ipc = ipc_lock(iface->ids, p)) != NULL) {
*pos = p + 1;
return ipc;
}
}
/* Out of range - return NULL to terminate iteration */
return NULL;
}
/*
* File positions: pos 0 -> header, pos n -> ipc id + 1.
* SeqFile iterator: iterator value locked shp or SEQ_TOKEN_START.
*/
static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
{
struct ipc_proc_iface *iface = s->private;
struct kern_ipc_perm *ipc;
loff_t p;
/*
* Take the lock - this will be released by the corresponding
* call to stop().
*/
down(&iface->ids->sem);
/* pos < 0 is invalid */
if (*pos < 0)
return NULL;
/* pos == 0 means header */
if (*pos == 0)
return SEQ_START_TOKEN;
/* Find the (pos-1)th ipc */
for (p = *pos - 1; p <= iface->ids->max_id; p++) {
if ((ipc = ipc_lock(iface->ids, p)) != NULL) {
*pos = p + 1;
return ipc;
}
}
return NULL;
}
static void sysvipc_proc_stop(struct seq_file *s, void *it)
{
struct kern_ipc_perm *ipc = it;
struct ipc_proc_iface *iface = s->private;
/* If we had a locked segment, release it */
if (ipc && ipc != SEQ_START_TOKEN)
ipc_unlock(ipc);
/* Release the lock we took in start() */
up(&iface->ids->sem);
}
static int sysvipc_proc_show(struct seq_file *s, void *it)
{
struct ipc_proc_iface *iface = s->private;
if (it == SEQ_START_TOKEN)
return seq_puts(s, iface->header);
return iface->show(s, it);
}
static struct seq_operations sysvipc_proc_seqops = {
.start = sysvipc_proc_start,
.stop = sysvipc_proc_stop,
.next = sysvipc_proc_next,
.show = sysvipc_proc_show,
};
static int sysvipc_proc_open(struct inode *inode, struct file *file) {
int ret;
struct seq_file *seq;
ret = seq_open(file, &sysvipc_proc_seqops);
if (!ret) {
seq = file->private_data;
seq->private = PDE(inode)->data;
}
return ret;
}
static struct file_operations sysvipc_proc_fops = {
.open = sysvipc_proc_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
#endif /* CONFIG_PROC_FS */
Jump to Line
Something went wrong with that request. Please try again.