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sem.c
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sem.c
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/*
* linux/ipc/sem.c
* Copyright (C) 1992 Krishna Balasubramanian
* Copyright (C) 1995 Eric Schenk, Bruno Haible
*
* IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995):
* This code underwent a massive rewrite in order to solve some problems
* with the original code. In particular the original code failed to
* wake up processes that were waiting for semval to go to 0 if the
* value went to 0 and was then incremented rapidly enough. In solving
* this problem I have also modified the implementation so that it
* processes pending operations in a FIFO manner, thus give a guarantee
* that processes waiting for a lock on the semaphore won't starve
* unless another locking process fails to unlock.
* In addition the following two changes in behavior have been introduced:
* - The original implementation of semop returned the value
* last semaphore element examined on success. This does not
* match the manual page specifications, and effectively
* allows the user to read the semaphore even if they do not
* have read permissions. The implementation now returns 0
* on success as stated in the manual page.
* - There is some confusion over whether the set of undo adjustments
* to be performed at exit should be done in an atomic manner.
* That is, if we are attempting to decrement the semval should we queue
* up and wait until we can do so legally?
* The original implementation attempted to do this.
* The current implementation does not do so. This is because I don't
* think it is the right thing (TM) to do, and because I couldn't
* see a clean way to get the old behavior with the new design.
* The POSIX standard and SVID should be consulted to determine
* what behavior is mandated.
*
* Further notes on refinement (Christoph Rohland, December 1998):
* - The POSIX standard says, that the undo adjustments simply should
* redo. So the current implementation is o.K.
* - The previous code had two flaws:
* 1) It actively gave the semaphore to the next waiting process
* sleeping on the semaphore. Since this process did not have the
* cpu this led to many unnecessary context switches and bad
* performance. Now we only check which process should be able to
* get the semaphore and if this process wants to reduce some
* semaphore value we simply wake it up without doing the
* operation. So it has to try to get it later. Thus e.g. the
* running process may reacquire the semaphore during the current
* time slice. If it only waits for zero or increases the semaphore,
* we do the operation in advance and wake it up.
* 2) It did not wake up all zero waiting processes. We try to do
* better but only get the semops right which only wait for zero or
* increase. If there are decrement operations in the operations
* array we do the same as before.
*
* With the incarnation of O(1) scheduler, it becomes unnecessary to perform
* check/retry algorithm for waking up blocked processes as the new scheduler
* is better at handling thread switch than the old one.
*
* /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <[email protected]>
*
* SMP-threaded, sysctl's added
* (c) 1999 Manfred Spraul <[email protected]>
* Enforced range limit on SEM_UNDO
* (c) 2001 Red Hat Inc <[email protected]>
* Lockless wakeup
* (c) 2003 Manfred Spraul <[email protected]>
*
* support for audit of ipc object properties and permission changes
* Dustin Kirkland <[email protected]>
*
* namespaces support
* OpenVZ, SWsoft Inc.
* Pavel Emelianov <[email protected]>
*/
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/time.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/seq_file.h>
#include <linux/rwsem.h>
#include <linux/nsproxy.h>
#include <asm/uaccess.h>
#include "util.h"
#define sem_ids(ns) (*((ns)->ids[IPC_SEM_IDS]))
#define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
#define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
#define sem_buildid(id, seq) ipc_buildid(id, seq)
static struct ipc_ids init_sem_ids;
static int newary(struct ipc_namespace *, struct ipc_params *);
static void freeary(struct ipc_namespace *, struct sem_array *);
#ifdef CONFIG_PROC_FS
static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
#endif
#define SEMMSL_FAST 256 /* 512 bytes on stack */
#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
/*
* linked list protection:
* sem_undo.id_next,
* sem_array.sem_pending{,last},
* sem_array.sem_undo: sem_lock() for read/write
* sem_undo.proc_next: only "current" is allowed to read/write that field.
*
*/
#define sc_semmsl sem_ctls[0]
#define sc_semmns sem_ctls[1]
#define sc_semopm sem_ctls[2]
#define sc_semmni sem_ctls[3]
static void __sem_init_ns(struct ipc_namespace *ns, struct ipc_ids *ids)
{
ns->ids[IPC_SEM_IDS] = ids;
ns->sc_semmsl = SEMMSL;
ns->sc_semmns = SEMMNS;
ns->sc_semopm = SEMOPM;
ns->sc_semmni = SEMMNI;
ns->used_sems = 0;
ipc_init_ids(ids);
}
int sem_init_ns(struct ipc_namespace *ns)
{
struct ipc_ids *ids;
ids = kmalloc(sizeof(struct ipc_ids), GFP_KERNEL);
if (ids == NULL)
return -ENOMEM;
__sem_init_ns(ns, ids);
return 0;
}
void sem_exit_ns(struct ipc_namespace *ns)
{
struct sem_array *sma;
int next_id;
int total, in_use;
down_write(&sem_ids(ns).rw_mutex);
in_use = sem_ids(ns).in_use;
for (total = 0, next_id = 0; total < in_use; next_id++) {
sma = idr_find(&sem_ids(ns).ipcs_idr, next_id);
if (sma == NULL)
continue;
ipc_lock_by_ptr(&sma->sem_perm);
freeary(ns, sma);
total++;
}
up_write(&sem_ids(ns).rw_mutex);
kfree(ns->ids[IPC_SEM_IDS]);
ns->ids[IPC_SEM_IDS] = NULL;
}
void __init sem_init (void)
{
__sem_init_ns(&init_ipc_ns, &init_sem_ids);
ipc_init_proc_interface("sysvipc/sem",
" key semid perms nsems uid gid cuid cgid otime ctime\n",
IPC_SEM_IDS, sysvipc_sem_proc_show);
}
/*
* This routine is called in the paths where the rw_mutex is held to protect
* access to the idr tree.
*/
static inline struct sem_array *sem_lock_check_down(struct ipc_namespace *ns,
int id)
{
struct kern_ipc_perm *ipcp = ipc_lock_check_down(&sem_ids(ns), id);
return container_of(ipcp, struct sem_array, sem_perm);
}
/*
* sem_lock_(check_) routines are called in the paths where the rw_mutex
* is not held.
*/
static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
{
struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
return container_of(ipcp, struct sem_array, sem_perm);
}
static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
int id)
{
struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);
return container_of(ipcp, struct sem_array, sem_perm);
}
static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
{
ipc_rmid(&sem_ids(ns), &s->sem_perm);
}
/*
* Lockless wakeup algorithm:
* Without the check/retry algorithm a lockless wakeup is possible:
* - queue.status is initialized to -EINTR before blocking.
* - wakeup is performed by
* * unlinking the queue entry from sma->sem_pending
* * setting queue.status to IN_WAKEUP
* This is the notification for the blocked thread that a
* result value is imminent.
* * call wake_up_process
* * set queue.status to the final value.
* - the previously blocked thread checks queue.status:
* * if it's IN_WAKEUP, then it must wait until the value changes
* * if it's not -EINTR, then the operation was completed by
* update_queue. semtimedop can return queue.status without
* performing any operation on the sem array.
* * otherwise it must acquire the spinlock and check what's up.
*
* The two-stage algorithm is necessary to protect against the following
* races:
* - if queue.status is set after wake_up_process, then the woken up idle
* thread could race forward and try (and fail) to acquire sma->lock
* before update_queue had a chance to set queue.status
* - if queue.status is written before wake_up_process and if the
* blocked process is woken up by a signal between writing
* queue.status and the wake_up_process, then the woken up
* process could return from semtimedop and die by calling
* sys_exit before wake_up_process is called. Then wake_up_process
* will oops, because the task structure is already invalid.
* (yes, this happened on s390 with sysv msg).
*
*/
#define IN_WAKEUP 1
/**
* newary - Create a new semaphore set
* @ns: namespace
* @params: ptr to the structure that contains key, semflg and nsems
*
* Called with sem_ids.rw_mutex held (as a writer)
*/
static int newary(struct ipc_namespace *ns, struct ipc_params *params)
{
int id;
int retval;
struct sem_array *sma;
int size;
key_t key = params->key;
int nsems = params->u.nsems;
int semflg = params->flg;
if (!nsems)
return -EINVAL;
if (ns->used_sems + nsems > ns->sc_semmns)
return -ENOSPC;
size = sizeof (*sma) + nsems * sizeof (struct sem);
sma = ipc_rcu_alloc(size);
if (!sma) {
return -ENOMEM;
}
memset (sma, 0, size);
sma->sem_perm.mode = (semflg & S_IRWXUGO);
sma->sem_perm.key = key;
sma->sem_perm.security = NULL;
retval = security_sem_alloc(sma);
if (retval) {
ipc_rcu_putref(sma);
return retval;
}
id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
if (id < 0) {
security_sem_free(sma);
ipc_rcu_putref(sma);
return id;
}
ns->used_sems += nsems;
sma->sem_perm.id = sem_buildid(id, sma->sem_perm.seq);
sma->sem_base = (struct sem *) &sma[1];
/* sma->sem_pending = NULL; */
sma->sem_pending_last = &sma->sem_pending;
/* sma->undo = NULL; */
sma->sem_nsems = nsems;
sma->sem_ctime = get_seconds();
sem_unlock(sma);
return sma->sem_perm.id;
}
/*
* Called with sem_ids.rw_mutex and ipcp locked.
*/
static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
{
struct sem_array *sma;
sma = container_of(ipcp, struct sem_array, sem_perm);
return security_sem_associate(sma, semflg);
}
/*
* Called with sem_ids.rw_mutex and ipcp locked.
*/
static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
struct ipc_params *params)
{
struct sem_array *sma;
sma = container_of(ipcp, struct sem_array, sem_perm);
if (params->u.nsems > sma->sem_nsems)
return -EINVAL;
return 0;
}
asmlinkage long sys_semget(key_t key, int nsems, int semflg)
{
struct ipc_namespace *ns;
struct ipc_ops sem_ops;
struct ipc_params sem_params;
ns = current->nsproxy->ipc_ns;
if (nsems < 0 || nsems > ns->sc_semmsl)
return -EINVAL;
sem_ops.getnew = newary;
sem_ops.associate = sem_security;
sem_ops.more_checks = sem_more_checks;
sem_params.key = key;
sem_params.flg = semflg;
sem_params.u.nsems = nsems;
return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
}
/* Manage the doubly linked list sma->sem_pending as a FIFO:
* insert new queue elements at the tail sma->sem_pending_last.
*/
static inline void append_to_queue (struct sem_array * sma,
struct sem_queue * q)
{
*(q->prev = sma->sem_pending_last) = q;
*(sma->sem_pending_last = &q->next) = NULL;
}
static inline void prepend_to_queue (struct sem_array * sma,
struct sem_queue * q)
{
q->next = sma->sem_pending;
*(q->prev = &sma->sem_pending) = q;
if (q->next)
q->next->prev = &q->next;
else /* sma->sem_pending_last == &sma->sem_pending */
sma->sem_pending_last = &q->next;
}
static inline void remove_from_queue (struct sem_array * sma,
struct sem_queue * q)
{
*(q->prev) = q->next;
if (q->next)
q->next->prev = q->prev;
else /* sma->sem_pending_last == &q->next */
sma->sem_pending_last = q->prev;
q->prev = NULL; /* mark as removed */
}
/*
* Determine whether a sequence of semaphore operations would succeed
* all at once. Return 0 if yes, 1 if need to sleep, else return error code.
*/
static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
int nsops, struct sem_undo *un, int pid)
{
int result, sem_op;
struct sembuf *sop;
struct sem * curr;
for (sop = sops; sop < sops + nsops; sop++) {
curr = sma->sem_base + sop->sem_num;
sem_op = sop->sem_op;
result = curr->semval;
if (!sem_op && result)
goto would_block;
result += sem_op;
if (result < 0)
goto would_block;
if (result > SEMVMX)
goto out_of_range;
if (sop->sem_flg & SEM_UNDO) {
int undo = un->semadj[sop->sem_num] - sem_op;
/*
* Exceeding the undo range is an error.
*/
if (undo < (-SEMAEM - 1) || undo > SEMAEM)
goto out_of_range;
}
curr->semval = result;
}
sop--;
while (sop >= sops) {
sma->sem_base[sop->sem_num].sempid = pid;
if (sop->sem_flg & SEM_UNDO)
un->semadj[sop->sem_num] -= sop->sem_op;
sop--;
}
sma->sem_otime = get_seconds();
return 0;
out_of_range:
result = -ERANGE;
goto undo;
would_block:
if (sop->sem_flg & IPC_NOWAIT)
result = -EAGAIN;
else
result = 1;
undo:
sop--;
while (sop >= sops) {
sma->sem_base[sop->sem_num].semval -= sop->sem_op;
sop--;
}
return result;
}
/* Go through the pending queue for the indicated semaphore
* looking for tasks that can be completed.
*/
static void update_queue (struct sem_array * sma)
{
int error;
struct sem_queue * q;
q = sma->sem_pending;
while(q) {
error = try_atomic_semop(sma, q->sops, q->nsops,
q->undo, q->pid);
/* Does q->sleeper still need to sleep? */
if (error <= 0) {
struct sem_queue *n;
remove_from_queue(sma,q);
q->status = IN_WAKEUP;
/*
* Continue scanning. The next operation
* that must be checked depends on the type of the
* completed operation:
* - if the operation modified the array, then
* restart from the head of the queue and
* check for threads that might be waiting
* for semaphore values to become 0.
* - if the operation didn't modify the array,
* then just continue.
*/
if (q->alter)
n = sma->sem_pending;
else
n = q->next;
wake_up_process(q->sleeper);
/* hands-off: q will disappear immediately after
* writing q->status.
*/
smp_wmb();
q->status = error;
q = n;
} else {
q = q->next;
}
}
}
/* The following counts are associated to each semaphore:
* semncnt number of tasks waiting on semval being nonzero
* semzcnt number of tasks waiting on semval being zero
* This model assumes that a task waits on exactly one semaphore.
* Since semaphore operations are to be performed atomically, tasks actually
* wait on a whole sequence of semaphores simultaneously.
* The counts we return here are a rough approximation, but still
* warrant that semncnt+semzcnt>0 if the task is on the pending queue.
*/
static int count_semncnt (struct sem_array * sma, ushort semnum)
{
int semncnt;
struct sem_queue * q;
semncnt = 0;
for (q = sma->sem_pending; q; q = q->next) {
struct sembuf * sops = q->sops;
int nsops = q->nsops;
int i;
for (i = 0; i < nsops; i++)
if (sops[i].sem_num == semnum
&& (sops[i].sem_op < 0)
&& !(sops[i].sem_flg & IPC_NOWAIT))
semncnt++;
}
return semncnt;
}
static int count_semzcnt (struct sem_array * sma, ushort semnum)
{
int semzcnt;
struct sem_queue * q;
semzcnt = 0;
for (q = sma->sem_pending; q; q = q->next) {
struct sembuf * sops = q->sops;
int nsops = q->nsops;
int i;
for (i = 0; i < nsops; i++)
if (sops[i].sem_num == semnum
&& (sops[i].sem_op == 0)
&& !(sops[i].sem_flg & IPC_NOWAIT))
semzcnt++;
}
return semzcnt;
}
/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
* as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
* remains locked on exit.
*/
static void freeary(struct ipc_namespace *ns, struct sem_array *sma)
{
struct sem_undo *un;
struct sem_queue *q;
/* Invalidate the existing undo structures for this semaphore set.
* (They will be freed without any further action in exit_sem()
* or during the next semop.)
*/
for (un = sma->undo; un; un = un->id_next)
un->semid = -1;
/* Wake up all pending processes and let them fail with EIDRM. */
q = sma->sem_pending;
while(q) {
struct sem_queue *n;
/* lazy remove_from_queue: we are killing the whole queue */
q->prev = NULL;
n = q->next;
q->status = IN_WAKEUP;
wake_up_process(q->sleeper); /* doesn't sleep */
smp_wmb();
q->status = -EIDRM; /* hands-off q */
q = n;
}
/* Remove the semaphore set from the IDR */
sem_rmid(ns, sma);
sem_unlock(sma);
ns->used_sems -= sma->sem_nsems;
security_sem_free(sma);
ipc_rcu_putref(sma);
}
static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
{
switch(version) {
case IPC_64:
return copy_to_user(buf, in, sizeof(*in));
case IPC_OLD:
{
struct semid_ds out;
ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
out.sem_otime = in->sem_otime;
out.sem_ctime = in->sem_ctime;
out.sem_nsems = in->sem_nsems;
return copy_to_user(buf, &out, sizeof(out));
}
default:
return -EINVAL;
}
}
static int semctl_nolock(struct ipc_namespace *ns, int semid, int semnum,
int cmd, int version, union semun arg)
{
int err = -EINVAL;
struct sem_array *sma;
switch(cmd) {
case IPC_INFO:
case SEM_INFO:
{
struct seminfo seminfo;
int max_id;
err = security_sem_semctl(NULL, cmd);
if (err)
return err;
memset(&seminfo,0,sizeof(seminfo));
seminfo.semmni = ns->sc_semmni;
seminfo.semmns = ns->sc_semmns;
seminfo.semmsl = ns->sc_semmsl;
seminfo.semopm = ns->sc_semopm;
seminfo.semvmx = SEMVMX;
seminfo.semmnu = SEMMNU;
seminfo.semmap = SEMMAP;
seminfo.semume = SEMUME;
down_read(&sem_ids(ns).rw_mutex);
if (cmd == SEM_INFO) {
seminfo.semusz = sem_ids(ns).in_use;
seminfo.semaem = ns->used_sems;
} else {
seminfo.semusz = SEMUSZ;
seminfo.semaem = SEMAEM;
}
max_id = ipc_get_maxid(&sem_ids(ns));
up_read(&sem_ids(ns).rw_mutex);
if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
return -EFAULT;
return (max_id < 0) ? 0: max_id;
}
case SEM_STAT:
{
struct semid64_ds tbuf;
int id;
sma = sem_lock(ns, semid);
if (IS_ERR(sma))
return PTR_ERR(sma);
err = -EACCES;
if (ipcperms (&sma->sem_perm, S_IRUGO))
goto out_unlock;
err = security_sem_semctl(sma, cmd);
if (err)
goto out_unlock;
id = sma->sem_perm.id;
memset(&tbuf, 0, sizeof(tbuf));
kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
tbuf.sem_otime = sma->sem_otime;
tbuf.sem_ctime = sma->sem_ctime;
tbuf.sem_nsems = sma->sem_nsems;
sem_unlock(sma);
if (copy_semid_to_user (arg.buf, &tbuf, version))
return -EFAULT;
return id;
}
default:
return -EINVAL;
}
return err;
out_unlock:
sem_unlock(sma);
return err;
}
static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
int cmd, int version, union semun arg)
{
struct sem_array *sma;
struct sem* curr;
int err;
ushort fast_sem_io[SEMMSL_FAST];
ushort* sem_io = fast_sem_io;
int nsems;
sma = sem_lock_check(ns, semid);
if (IS_ERR(sma))
return PTR_ERR(sma);
nsems = sma->sem_nsems;
err = -EACCES;
if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO))
goto out_unlock;
err = security_sem_semctl(sma, cmd);
if (err)
goto out_unlock;
err = -EACCES;
switch (cmd) {
case GETALL:
{
ushort __user *array = arg.array;
int i;
if(nsems > SEMMSL_FAST) {
ipc_rcu_getref(sma);
sem_unlock(sma);
sem_io = ipc_alloc(sizeof(ushort)*nsems);
if(sem_io == NULL) {
ipc_lock_by_ptr(&sma->sem_perm);
ipc_rcu_putref(sma);
sem_unlock(sma);
return -ENOMEM;
}
ipc_lock_by_ptr(&sma->sem_perm);
ipc_rcu_putref(sma);
if (sma->sem_perm.deleted) {
sem_unlock(sma);
err = -EIDRM;
goto out_free;
}
}
for (i = 0; i < sma->sem_nsems; i++)
sem_io[i] = sma->sem_base[i].semval;
sem_unlock(sma);
err = 0;
if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
err = -EFAULT;
goto out_free;
}
case SETALL:
{
int i;
struct sem_undo *un;
ipc_rcu_getref(sma);
sem_unlock(sma);
if(nsems > SEMMSL_FAST) {
sem_io = ipc_alloc(sizeof(ushort)*nsems);
if(sem_io == NULL) {
ipc_lock_by_ptr(&sma->sem_perm);
ipc_rcu_putref(sma);
sem_unlock(sma);
return -ENOMEM;
}
}
if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
ipc_lock_by_ptr(&sma->sem_perm);
ipc_rcu_putref(sma);
sem_unlock(sma);
err = -EFAULT;
goto out_free;
}
for (i = 0; i < nsems; i++) {
if (sem_io[i] > SEMVMX) {
ipc_lock_by_ptr(&sma->sem_perm);
ipc_rcu_putref(sma);
sem_unlock(sma);
err = -ERANGE;
goto out_free;
}
}
ipc_lock_by_ptr(&sma->sem_perm);
ipc_rcu_putref(sma);
if (sma->sem_perm.deleted) {
sem_unlock(sma);
err = -EIDRM;
goto out_free;
}
for (i = 0; i < nsems; i++)
sma->sem_base[i].semval = sem_io[i];
for (un = sma->undo; un; un = un->id_next)
for (i = 0; i < nsems; i++)
un->semadj[i] = 0;
sma->sem_ctime = get_seconds();
/* maybe some queued-up processes were waiting for this */
update_queue(sma);
err = 0;
goto out_unlock;
}
case IPC_STAT:
{
struct semid64_ds tbuf;
memset(&tbuf,0,sizeof(tbuf));
kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
tbuf.sem_otime = sma->sem_otime;
tbuf.sem_ctime = sma->sem_ctime;
tbuf.sem_nsems = sma->sem_nsems;
sem_unlock(sma);
if (copy_semid_to_user (arg.buf, &tbuf, version))
return -EFAULT;
return 0;
}
/* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
}
err = -EINVAL;
if(semnum < 0 || semnum >= nsems)
goto out_unlock;
curr = &sma->sem_base[semnum];
switch (cmd) {
case GETVAL:
err = curr->semval;
goto out_unlock;
case GETPID:
err = curr->sempid;
goto out_unlock;
case GETNCNT:
err = count_semncnt(sma,semnum);
goto out_unlock;
case GETZCNT:
err = count_semzcnt(sma,semnum);
goto out_unlock;
case SETVAL:
{
int val = arg.val;
struct sem_undo *un;
err = -ERANGE;
if (val > SEMVMX || val < 0)
goto out_unlock;
for (un = sma->undo; un; un = un->id_next)
un->semadj[semnum] = 0;
curr->semval = val;
curr->sempid = task_tgid_vnr(current);
sma->sem_ctime = get_seconds();
/* maybe some queued-up processes were waiting for this */
update_queue(sma);
err = 0;
goto out_unlock;
}
}
out_unlock:
sem_unlock(sma);
out_free:
if(sem_io != fast_sem_io)
ipc_free(sem_io, sizeof(ushort)*nsems);
return err;
}
struct sem_setbuf {
uid_t uid;
gid_t gid;
mode_t mode;
};
static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __user *buf, int version)
{
switch(version) {
case IPC_64:
{
struct semid64_ds tbuf;
if(copy_from_user(&tbuf, buf, sizeof(tbuf)))
return -EFAULT;
out->uid = tbuf.sem_perm.uid;
out->gid = tbuf.sem_perm.gid;
out->mode = tbuf.sem_perm.mode;
return 0;
}
case IPC_OLD:
{
struct semid_ds tbuf_old;
if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
return -EFAULT;
out->uid = tbuf_old.sem_perm.uid;
out->gid = tbuf_old.sem_perm.gid;
out->mode = tbuf_old.sem_perm.mode;
return 0;
}
default:
return -EINVAL;
}
}
static int semctl_down(struct ipc_namespace *ns, int semid, int semnum,
int cmd, int version, union semun arg)
{
struct sem_array *sma;
int err;
struct sem_setbuf uninitialized_var(setbuf);
struct kern_ipc_perm *ipcp;
if(cmd == IPC_SET) {
if(copy_semid_from_user (&setbuf, arg.buf, version))
return -EFAULT;
}
sma = sem_lock_check_down(ns, semid);
if (IS_ERR(sma))
return PTR_ERR(sma);
ipcp = &sma->sem_perm;
err = audit_ipc_obj(ipcp);
if (err)
goto out_unlock;
if (cmd == IPC_SET) {
err = audit_ipc_set_perm(0, setbuf.uid, setbuf.gid, setbuf.mode);
if (err)
goto out_unlock;
}
if (current->euid != ipcp->cuid &&
current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN)) {
err=-EPERM;
goto out_unlock;
}
err = security_sem_semctl(sma, cmd);
if (err)
goto out_unlock;
switch(cmd){
case IPC_RMID:
freeary(ns, sma);
err = 0;
break;
case IPC_SET:
ipcp->uid = setbuf.uid;
ipcp->gid = setbuf.gid;
ipcp->mode = (ipcp->mode & ~S_IRWXUGO)
| (setbuf.mode & S_IRWXUGO);
sma->sem_ctime = get_seconds();
sem_unlock(sma);
err = 0;
break;
default:
sem_unlock(sma);
err = -EINVAL;
break;
}
return err;
out_unlock:
sem_unlock(sma);
return err;
}
asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
{
int err = -EINVAL;
int version;
struct ipc_namespace *ns;
if (semid < 0)
return -EINVAL;
version = ipc_parse_version(&cmd);
ns = current->nsproxy->ipc_ns;
switch(cmd) {
case IPC_INFO:
case SEM_INFO:
case SEM_STAT:
err = semctl_nolock(ns,semid,semnum,cmd,version,arg);
return err;
case GETALL:
case GETVAL:
case GETPID:
case GETNCNT:
case GETZCNT:
case IPC_STAT:
case SETVAL:
case SETALL:
err = semctl_main(ns,semid,semnum,cmd,version,arg);
return err;
case IPC_RMID:
case IPC_SET:
down_write(&sem_ids(ns).rw_mutex);
err = semctl_down(ns,semid,semnum,cmd,version,arg);
up_write(&sem_ids(ns).rw_mutex);
return err;
default:
return -EINVAL;
}
}