mirror of
https://github.com/FEX-Emu/linux.git
synced 2024-12-24 02:18:54 +00:00
1efdb69b0b
- Store the ipc owner and creator with a kuid - Store the ipc group and the crators group with a kgid. - Add error handling to ipc_update_perms, allowing it to fail if the uids and gids can not be converted to kuids or kgids. - Modify the proc files to display the ipc creator and owner in the user namespace of the opener of the proc file. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
1699 lines
42 KiB
C
1699 lines
42 KiB
C
/*
|
|
* linux/ipc/sem.c
|
|
* Copyright (C) 1992 Krishna Balasubramanian
|
|
* Copyright (C) 1995 Eric Schenk, Bruno Haible
|
|
*
|
|
* /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
|
|
*
|
|
* SMP-threaded, sysctl's added
|
|
* (c) 1999 Manfred Spraul <manfred@colorfullife.com>
|
|
* Enforced range limit on SEM_UNDO
|
|
* (c) 2001 Red Hat Inc
|
|
* Lockless wakeup
|
|
* (c) 2003 Manfred Spraul <manfred@colorfullife.com>
|
|
* Further wakeup optimizations, documentation
|
|
* (c) 2010 Manfred Spraul <manfred@colorfullife.com>
|
|
*
|
|
* support for audit of ipc object properties and permission changes
|
|
* Dustin Kirkland <dustin.kirkland@us.ibm.com>
|
|
*
|
|
* namespaces support
|
|
* OpenVZ, SWsoft Inc.
|
|
* Pavel Emelianov <xemul@openvz.org>
|
|
*
|
|
* Implementation notes: (May 2010)
|
|
* This file implements System V semaphores.
|
|
*
|
|
* User space visible behavior:
|
|
* - FIFO ordering for semop() operations (just FIFO, not starvation
|
|
* protection)
|
|
* - multiple semaphore operations that alter the same semaphore in
|
|
* one semop() are handled.
|
|
* - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
|
|
* SETALL calls.
|
|
* - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
|
|
* - undo adjustments at process exit are limited to 0..SEMVMX.
|
|
* - namespace are supported.
|
|
* - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing
|
|
* to /proc/sys/kernel/sem.
|
|
* - statistics about the usage are reported in /proc/sysvipc/sem.
|
|
*
|
|
* Internals:
|
|
* - scalability:
|
|
* - all global variables are read-mostly.
|
|
* - semop() calls and semctl(RMID) are synchronized by RCU.
|
|
* - most operations do write operations (actually: spin_lock calls) to
|
|
* the per-semaphore array structure.
|
|
* Thus: Perfect SMP scaling between independent semaphore arrays.
|
|
* If multiple semaphores in one array are used, then cache line
|
|
* trashing on the semaphore array spinlock will limit the scaling.
|
|
* - semncnt and semzcnt are calculated on demand in count_semncnt() and
|
|
* count_semzcnt()
|
|
* - the task that performs a successful semop() scans the list of all
|
|
* sleeping tasks and completes any pending operations that can be fulfilled.
|
|
* Semaphores are actively given to waiting tasks (necessary for FIFO).
|
|
* (see update_queue())
|
|
* - To improve the scalability, the actual wake-up calls are performed after
|
|
* dropping all locks. (see wake_up_sem_queue_prepare(),
|
|
* wake_up_sem_queue_do())
|
|
* - All work is done by the waker, the woken up task does not have to do
|
|
* anything - not even acquiring a lock or dropping a refcount.
|
|
* - A woken up task may not even touch the semaphore array anymore, it may
|
|
* have been destroyed already by a semctl(RMID).
|
|
* - The synchronizations between wake-ups due to a timeout/signal and a
|
|
* wake-up due to a completed semaphore operation is achieved by using an
|
|
* intermediate state (IN_WAKEUP).
|
|
* - UNDO values are stored in an array (one per process and per
|
|
* semaphore array, lazily allocated). For backwards compatibility, multiple
|
|
* modes for the UNDO variables are supported (per process, per thread)
|
|
* (see copy_semundo, CLONE_SYSVSEM)
|
|
* - There are two lists of the pending operations: a per-array list
|
|
* and per-semaphore list (stored in the array). This allows to achieve FIFO
|
|
* ordering without always scanning all pending operations.
|
|
* The worst-case behavior is nevertheless O(N^2) for N wakeups.
|
|
*/
|
|
|
|
#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 <linux/ipc_namespace.h>
|
|
|
|
#include <asm/uaccess.h>
|
|
#include "util.h"
|
|
|
|
/* One semaphore structure for each semaphore in the system. */
|
|
struct sem {
|
|
int semval; /* current value */
|
|
int sempid; /* pid of last operation */
|
|
struct list_head sem_pending; /* pending single-sop operations */
|
|
};
|
|
|
|
/* One queue for each sleeping process in the system. */
|
|
struct sem_queue {
|
|
struct list_head simple_list; /* queue of pending operations */
|
|
struct list_head list; /* queue of pending operations */
|
|
struct task_struct *sleeper; /* this process */
|
|
struct sem_undo *undo; /* undo structure */
|
|
int pid; /* process id of requesting process */
|
|
int status; /* completion status of operation */
|
|
struct sembuf *sops; /* array of pending operations */
|
|
int nsops; /* number of operations */
|
|
int alter; /* does *sops alter the array? */
|
|
};
|
|
|
|
/* Each task has a list of undo requests. They are executed automatically
|
|
* when the process exits.
|
|
*/
|
|
struct sem_undo {
|
|
struct list_head list_proc; /* per-process list: *
|
|
* all undos from one process
|
|
* rcu protected */
|
|
struct rcu_head rcu; /* rcu struct for sem_undo */
|
|
struct sem_undo_list *ulp; /* back ptr to sem_undo_list */
|
|
struct list_head list_id; /* per semaphore array list:
|
|
* all undos for one array */
|
|
int semid; /* semaphore set identifier */
|
|
short *semadj; /* array of adjustments */
|
|
/* one per semaphore */
|
|
};
|
|
|
|
/* sem_undo_list controls shared access to the list of sem_undo structures
|
|
* that may be shared among all a CLONE_SYSVSEM task group.
|
|
*/
|
|
struct sem_undo_list {
|
|
atomic_t refcnt;
|
|
spinlock_t lock;
|
|
struct list_head list_proc;
|
|
};
|
|
|
|
|
|
#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)
|
|
|
|
static int newary(struct ipc_namespace *, struct ipc_params *);
|
|
static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
|
|
#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]
|
|
|
|
void sem_init_ns(struct ipc_namespace *ns)
|
|
{
|
|
ns->sc_semmsl = SEMMSL;
|
|
ns->sc_semmns = SEMMNS;
|
|
ns->sc_semopm = SEMOPM;
|
|
ns->sc_semmni = SEMMNI;
|
|
ns->used_sems = 0;
|
|
ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
|
|
}
|
|
|
|
#ifdef CONFIG_IPC_NS
|
|
void sem_exit_ns(struct ipc_namespace *ns)
|
|
{
|
|
free_ipcs(ns, &sem_ids(ns), freeary);
|
|
idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
|
|
}
|
|
#endif
|
|
|
|
void __init sem_init (void)
|
|
{
|
|
sem_init_ns(&init_ipc_ns);
|
|
ipc_init_proc_interface("sysvipc/sem",
|
|
" key semid perms nsems uid gid cuid cgid otime ctime\n",
|
|
IPC_SEM_IDS, sysvipc_sem_proc_show);
|
|
}
|
|
|
|
/*
|
|
* 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);
|
|
|
|
if (IS_ERR(ipcp))
|
|
return (struct sem_array *)ipcp;
|
|
|
|
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);
|
|
|
|
if (IS_ERR(ipcp))
|
|
return (struct sem_array *)ipcp;
|
|
|
|
return container_of(ipcp, struct sem_array, sem_perm);
|
|
}
|
|
|
|
static inline void sem_lock_and_putref(struct sem_array *sma)
|
|
{
|
|
ipc_lock_by_ptr(&sma->sem_perm);
|
|
ipc_rcu_putref(sma);
|
|
}
|
|
|
|
static inline void sem_getref_and_unlock(struct sem_array *sma)
|
|
{
|
|
ipc_rcu_getref(sma);
|
|
ipc_unlock(&(sma)->sem_perm);
|
|
}
|
|
|
|
static inline void sem_putref(struct sem_array *sma)
|
|
{
|
|
ipc_lock_by_ptr(&sma->sem_perm);
|
|
ipc_rcu_putref(sma);
|
|
ipc_unlock(&(sma)->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;
|
|
int i;
|
|
|
|
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_base = (struct sem *) &sma[1];
|
|
|
|
for (i = 0; i < nsems; i++)
|
|
INIT_LIST_HEAD(&sma->sem_base[i].sem_pending);
|
|
|
|
sma->complex_count = 0;
|
|
INIT_LIST_HEAD(&sma->sem_pending);
|
|
INIT_LIST_HEAD(&sma->list_id);
|
|
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;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(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);
|
|
}
|
|
|
|
/*
|
|
* 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--;
|
|
}
|
|
|
|
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;
|
|
}
|
|
|
|
/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
|
|
* @q: queue entry that must be signaled
|
|
* @error: Error value for the signal
|
|
*
|
|
* Prepare the wake-up of the queue entry q.
|
|
*/
|
|
static void wake_up_sem_queue_prepare(struct list_head *pt,
|
|
struct sem_queue *q, int error)
|
|
{
|
|
if (list_empty(pt)) {
|
|
/*
|
|
* Hold preempt off so that we don't get preempted and have the
|
|
* wakee busy-wait until we're scheduled back on.
|
|
*/
|
|
preempt_disable();
|
|
}
|
|
q->status = IN_WAKEUP;
|
|
q->pid = error;
|
|
|
|
list_add_tail(&q->simple_list, pt);
|
|
}
|
|
|
|
/**
|
|
* wake_up_sem_queue_do(pt) - do the actual wake-up
|
|
* @pt: list of tasks to be woken up
|
|
*
|
|
* Do the actual wake-up.
|
|
* The function is called without any locks held, thus the semaphore array
|
|
* could be destroyed already and the tasks can disappear as soon as the
|
|
* status is set to the actual return code.
|
|
*/
|
|
static void wake_up_sem_queue_do(struct list_head *pt)
|
|
{
|
|
struct sem_queue *q, *t;
|
|
int did_something;
|
|
|
|
did_something = !list_empty(pt);
|
|
list_for_each_entry_safe(q, t, pt, simple_list) {
|
|
wake_up_process(q->sleeper);
|
|
/* q can disappear immediately after writing q->status. */
|
|
smp_wmb();
|
|
q->status = q->pid;
|
|
}
|
|
if (did_something)
|
|
preempt_enable();
|
|
}
|
|
|
|
static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
|
|
{
|
|
list_del(&q->list);
|
|
if (q->nsops == 1)
|
|
list_del(&q->simple_list);
|
|
else
|
|
sma->complex_count--;
|
|
}
|
|
|
|
/** check_restart(sma, q)
|
|
* @sma: semaphore array
|
|
* @q: the operation that just completed
|
|
*
|
|
* update_queue is O(N^2) when it restarts scanning the whole queue of
|
|
* waiting operations. Therefore this function checks if the restart is
|
|
* really necessary. It is called after a previously waiting operation
|
|
* was completed.
|
|
*/
|
|
static int check_restart(struct sem_array *sma, struct sem_queue *q)
|
|
{
|
|
struct sem *curr;
|
|
struct sem_queue *h;
|
|
|
|
/* if the operation didn't modify the array, then no restart */
|
|
if (q->alter == 0)
|
|
return 0;
|
|
|
|
/* pending complex operations are too difficult to analyse */
|
|
if (sma->complex_count)
|
|
return 1;
|
|
|
|
/* we were a sleeping complex operation. Too difficult */
|
|
if (q->nsops > 1)
|
|
return 1;
|
|
|
|
curr = sma->sem_base + q->sops[0].sem_num;
|
|
|
|
/* No-one waits on this queue */
|
|
if (list_empty(&curr->sem_pending))
|
|
return 0;
|
|
|
|
/* the new semaphore value */
|
|
if (curr->semval) {
|
|
/* It is impossible that someone waits for the new value:
|
|
* - q is a previously sleeping simple operation that
|
|
* altered the array. It must be a decrement, because
|
|
* simple increments never sleep.
|
|
* - The value is not 0, thus wait-for-zero won't proceed.
|
|
* - If there are older (higher priority) decrements
|
|
* in the queue, then they have observed the original
|
|
* semval value and couldn't proceed. The operation
|
|
* decremented to value - thus they won't proceed either.
|
|
*/
|
|
BUG_ON(q->sops[0].sem_op >= 0);
|
|
return 0;
|
|
}
|
|
/*
|
|
* semval is 0. Check if there are wait-for-zero semops.
|
|
* They must be the first entries in the per-semaphore simple queue
|
|
*/
|
|
h = list_first_entry(&curr->sem_pending, struct sem_queue, simple_list);
|
|
BUG_ON(h->nsops != 1);
|
|
BUG_ON(h->sops[0].sem_num != q->sops[0].sem_num);
|
|
|
|
/* Yes, there is a wait-for-zero semop. Restart */
|
|
if (h->sops[0].sem_op == 0)
|
|
return 1;
|
|
|
|
/* Again - no-one is waiting for the new value. */
|
|
return 0;
|
|
}
|
|
|
|
|
|
/**
|
|
* update_queue(sma, semnum): Look for tasks that can be completed.
|
|
* @sma: semaphore array.
|
|
* @semnum: semaphore that was modified.
|
|
* @pt: list head for the tasks that must be woken up.
|
|
*
|
|
* update_queue must be called after a semaphore in a semaphore array
|
|
* was modified. If multiple semaphore were modified, then @semnum
|
|
* must be set to -1.
|
|
* The tasks that must be woken up are added to @pt. The return code
|
|
* is stored in q->pid.
|
|
* The function return 1 if at least one semop was completed successfully.
|
|
*/
|
|
static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
|
|
{
|
|
struct sem_queue *q;
|
|
struct list_head *walk;
|
|
struct list_head *pending_list;
|
|
int offset;
|
|
int semop_completed = 0;
|
|
|
|
/* if there are complex operations around, then knowing the semaphore
|
|
* that was modified doesn't help us. Assume that multiple semaphores
|
|
* were modified.
|
|
*/
|
|
if (sma->complex_count)
|
|
semnum = -1;
|
|
|
|
if (semnum == -1) {
|
|
pending_list = &sma->sem_pending;
|
|
offset = offsetof(struct sem_queue, list);
|
|
} else {
|
|
pending_list = &sma->sem_base[semnum].sem_pending;
|
|
offset = offsetof(struct sem_queue, simple_list);
|
|
}
|
|
|
|
again:
|
|
walk = pending_list->next;
|
|
while (walk != pending_list) {
|
|
int error, restart;
|
|
|
|
q = (struct sem_queue *)((char *)walk - offset);
|
|
walk = walk->next;
|
|
|
|
/* If we are scanning the single sop, per-semaphore list of
|
|
* one semaphore and that semaphore is 0, then it is not
|
|
* necessary to scan the "alter" entries: simple increments
|
|
* that affect only one entry succeed immediately and cannot
|
|
* be in the per semaphore pending queue, and decrements
|
|
* cannot be successful if the value is already 0.
|
|
*/
|
|
if (semnum != -1 && sma->sem_base[semnum].semval == 0 &&
|
|
q->alter)
|
|
break;
|
|
|
|
error = try_atomic_semop(sma, q->sops, q->nsops,
|
|
q->undo, q->pid);
|
|
|
|
/* Does q->sleeper still need to sleep? */
|
|
if (error > 0)
|
|
continue;
|
|
|
|
unlink_queue(sma, q);
|
|
|
|
if (error) {
|
|
restart = 0;
|
|
} else {
|
|
semop_completed = 1;
|
|
restart = check_restart(sma, q);
|
|
}
|
|
|
|
wake_up_sem_queue_prepare(pt, q, error);
|
|
if (restart)
|
|
goto again;
|
|
}
|
|
return semop_completed;
|
|
}
|
|
|
|
/**
|
|
* do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
|
|
* @sma: semaphore array
|
|
* @sops: operations that were performed
|
|
* @nsops: number of operations
|
|
* @otime: force setting otime
|
|
* @pt: list head of the tasks that must be woken up.
|
|
*
|
|
* do_smart_update() does the required called to update_queue, based on the
|
|
* actual changes that were performed on the semaphore array.
|
|
* Note that the function does not do the actual wake-up: the caller is
|
|
* responsible for calling wake_up_sem_queue_do(@pt).
|
|
* It is safe to perform this call after dropping all locks.
|
|
*/
|
|
static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
|
|
int otime, struct list_head *pt)
|
|
{
|
|
int i;
|
|
|
|
if (sma->complex_count || sops == NULL) {
|
|
if (update_queue(sma, -1, pt))
|
|
otime = 1;
|
|
goto done;
|
|
}
|
|
|
|
for (i = 0; i < nsops; i++) {
|
|
if (sops[i].sem_op > 0 ||
|
|
(sops[i].sem_op < 0 &&
|
|
sma->sem_base[sops[i].sem_num].semval == 0))
|
|
if (update_queue(sma, sops[i].sem_num, pt))
|
|
otime = 1;
|
|
}
|
|
done:
|
|
if (otime)
|
|
sma->sem_otime = get_seconds();
|
|
}
|
|
|
|
|
|
/* 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;
|
|
list_for_each_entry(q, &sma->sem_pending, list) {
|
|
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;
|
|
list_for_each_entry(q, &sma->sem_pending, list) {
|
|
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 kern_ipc_perm *ipcp)
|
|
{
|
|
struct sem_undo *un, *tu;
|
|
struct sem_queue *q, *tq;
|
|
struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
|
|
struct list_head tasks;
|
|
|
|
/* Free the existing undo structures for this semaphore set. */
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
|
|
list_del(&un->list_id);
|
|
spin_lock(&un->ulp->lock);
|
|
un->semid = -1;
|
|
list_del_rcu(&un->list_proc);
|
|
spin_unlock(&un->ulp->lock);
|
|
kfree_rcu(un, rcu);
|
|
}
|
|
|
|
/* Wake up all pending processes and let them fail with EIDRM. */
|
|
INIT_LIST_HEAD(&tasks);
|
|
list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
|
|
unlink_queue(sma, q);
|
|
wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
|
|
}
|
|
|
|
/* Remove the semaphore set from the IDR */
|
|
sem_rmid(ns, sma);
|
|
sem_unlock(sma);
|
|
|
|
wake_up_sem_queue_do(&tasks);
|
|
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;
|
|
|
|
memset(&out, 0, sizeof(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 cmd, int version, union semun arg)
|
|
{
|
|
int err;
|
|
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 IPC_STAT:
|
|
case SEM_STAT:
|
|
{
|
|
struct semid64_ds tbuf;
|
|
int id;
|
|
|
|
if (cmd == SEM_STAT) {
|
|
sma = sem_lock(ns, semid);
|
|
if (IS_ERR(sma))
|
|
return PTR_ERR(sma);
|
|
id = sma->sem_perm.id;
|
|
} else {
|
|
sma = sem_lock_check(ns, semid);
|
|
if (IS_ERR(sma))
|
|
return PTR_ERR(sma);
|
|
id = 0;
|
|
}
|
|
|
|
err = -EACCES;
|
|
if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
|
|
goto out_unlock;
|
|
|
|
err = security_sem_semctl(sma, cmd);
|
|
if (err)
|
|
goto out_unlock;
|
|
|
|
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;
|
|
}
|
|
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;
|
|
struct list_head tasks;
|
|
|
|
sma = sem_lock_check(ns, semid);
|
|
if (IS_ERR(sma))
|
|
return PTR_ERR(sma);
|
|
|
|
INIT_LIST_HEAD(&tasks);
|
|
nsems = sma->sem_nsems;
|
|
|
|
err = -EACCES;
|
|
if (ipcperms(ns, &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) {
|
|
sem_getref_and_unlock(sma);
|
|
|
|
sem_io = ipc_alloc(sizeof(ushort)*nsems);
|
|
if(sem_io == NULL) {
|
|
sem_putref(sma);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
sem_lock_and_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;
|
|
|
|
sem_getref_and_unlock(sma);
|
|
|
|
if(nsems > SEMMSL_FAST) {
|
|
sem_io = ipc_alloc(sizeof(ushort)*nsems);
|
|
if(sem_io == NULL) {
|
|
sem_putref(sma);
|
|
return -ENOMEM;
|
|
}
|
|
}
|
|
|
|
if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
|
|
sem_putref(sma);
|
|
err = -EFAULT;
|
|
goto out_free;
|
|
}
|
|
|
|
for (i = 0; i < nsems; i++) {
|
|
if (sem_io[i] > SEMVMX) {
|
|
sem_putref(sma);
|
|
err = -ERANGE;
|
|
goto out_free;
|
|
}
|
|
}
|
|
sem_lock_and_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];
|
|
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_for_each_entry(un, &sma->list_id, list_id) {
|
|
for (i = 0; i < nsems; i++)
|
|
un->semadj[i] = 0;
|
|
}
|
|
sma->sem_ctime = get_seconds();
|
|
/* maybe some queued-up processes were waiting for this */
|
|
do_smart_update(sma, NULL, 0, 0, &tasks);
|
|
err = 0;
|
|
goto out_unlock;
|
|
}
|
|
/* 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;
|
|
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_for_each_entry(un, &sma->list_id, list_id)
|
|
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 */
|
|
do_smart_update(sma, NULL, 0, 0, &tasks);
|
|
err = 0;
|
|
goto out_unlock;
|
|
}
|
|
}
|
|
out_unlock:
|
|
sem_unlock(sma);
|
|
wake_up_sem_queue_do(&tasks);
|
|
|
|
out_free:
|
|
if(sem_io != fast_sem_io)
|
|
ipc_free(sem_io, sizeof(ushort)*nsems);
|
|
return err;
|
|
}
|
|
|
|
static inline unsigned long
|
|
copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
|
|
{
|
|
switch(version) {
|
|
case IPC_64:
|
|
if (copy_from_user(out, buf, sizeof(*out)))
|
|
return -EFAULT;
|
|
return 0;
|
|
case IPC_OLD:
|
|
{
|
|
struct semid_ds tbuf_old;
|
|
|
|
if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
|
|
return -EFAULT;
|
|
|
|
out->sem_perm.uid = tbuf_old.sem_perm.uid;
|
|
out->sem_perm.gid = tbuf_old.sem_perm.gid;
|
|
out->sem_perm.mode = tbuf_old.sem_perm.mode;
|
|
|
|
return 0;
|
|
}
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This function handles some semctl commands which require the rw_mutex
|
|
* to be held in write mode.
|
|
* NOTE: no locks must be held, the rw_mutex is taken inside this function.
|
|
*/
|
|
static int semctl_down(struct ipc_namespace *ns, int semid,
|
|
int cmd, int version, union semun arg)
|
|
{
|
|
struct sem_array *sma;
|
|
int err;
|
|
struct semid64_ds semid64;
|
|
struct kern_ipc_perm *ipcp;
|
|
|
|
if(cmd == IPC_SET) {
|
|
if (copy_semid_from_user(&semid64, arg.buf, version))
|
|
return -EFAULT;
|
|
}
|
|
|
|
ipcp = ipcctl_pre_down(ns, &sem_ids(ns), semid, cmd,
|
|
&semid64.sem_perm, 0);
|
|
if (IS_ERR(ipcp))
|
|
return PTR_ERR(ipcp);
|
|
|
|
sma = container_of(ipcp, struct sem_array, sem_perm);
|
|
|
|
err = security_sem_semctl(sma, cmd);
|
|
if (err)
|
|
goto out_unlock;
|
|
|
|
switch(cmd){
|
|
case IPC_RMID:
|
|
freeary(ns, ipcp);
|
|
goto out_up;
|
|
case IPC_SET:
|
|
err = ipc_update_perm(&semid64.sem_perm, ipcp);
|
|
if (err)
|
|
goto out_unlock;
|
|
sma->sem_ctime = get_seconds();
|
|
break;
|
|
default:
|
|
err = -EINVAL;
|
|
}
|
|
|
|
out_unlock:
|
|
sem_unlock(sma);
|
|
out_up:
|
|
up_write(&sem_ids(ns).rw_mutex);
|
|
return err;
|
|
}
|
|
|
|
SYSCALL_DEFINE(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 IPC_STAT:
|
|
case SEM_STAT:
|
|
err = semctl_nolock(ns, semid, cmd, version, arg);
|
|
return err;
|
|
case GETALL:
|
|
case GETVAL:
|
|
case GETPID:
|
|
case GETNCNT:
|
|
case GETZCNT:
|
|
case SETVAL:
|
|
case SETALL:
|
|
err = semctl_main(ns,semid,semnum,cmd,version,arg);
|
|
return err;
|
|
case IPC_RMID:
|
|
case IPC_SET:
|
|
err = semctl_down(ns, semid, cmd, version, arg);
|
|
return err;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
|
|
asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg)
|
|
{
|
|
return SYSC_semctl((int) semid, (int) semnum, (int) cmd, arg);
|
|
}
|
|
SYSCALL_ALIAS(sys_semctl, SyS_semctl);
|
|
#endif
|
|
|
|
/* If the task doesn't already have a undo_list, then allocate one
|
|
* here. We guarantee there is only one thread using this undo list,
|
|
* and current is THE ONE
|
|
*
|
|
* If this allocation and assignment succeeds, but later
|
|
* portions of this code fail, there is no need to free the sem_undo_list.
|
|
* Just let it stay associated with the task, and it'll be freed later
|
|
* at exit time.
|
|
*
|
|
* This can block, so callers must hold no locks.
|
|
*/
|
|
static inline int get_undo_list(struct sem_undo_list **undo_listp)
|
|
{
|
|
struct sem_undo_list *undo_list;
|
|
|
|
undo_list = current->sysvsem.undo_list;
|
|
if (!undo_list) {
|
|
undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
|
|
if (undo_list == NULL)
|
|
return -ENOMEM;
|
|
spin_lock_init(&undo_list->lock);
|
|
atomic_set(&undo_list->refcnt, 1);
|
|
INIT_LIST_HEAD(&undo_list->list_proc);
|
|
|
|
current->sysvsem.undo_list = undo_list;
|
|
}
|
|
*undo_listp = undo_list;
|
|
return 0;
|
|
}
|
|
|
|
static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
|
|
{
|
|
struct sem_undo *un;
|
|
|
|
list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
|
|
if (un->semid == semid)
|
|
return un;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
|
|
{
|
|
struct sem_undo *un;
|
|
|
|
assert_spin_locked(&ulp->lock);
|
|
|
|
un = __lookup_undo(ulp, semid);
|
|
if (un) {
|
|
list_del_rcu(&un->list_proc);
|
|
list_add_rcu(&un->list_proc, &ulp->list_proc);
|
|
}
|
|
return un;
|
|
}
|
|
|
|
/**
|
|
* find_alloc_undo - Lookup (and if not present create) undo array
|
|
* @ns: namespace
|
|
* @semid: semaphore array id
|
|
*
|
|
* The function looks up (and if not present creates) the undo structure.
|
|
* The size of the undo structure depends on the size of the semaphore
|
|
* array, thus the alloc path is not that straightforward.
|
|
* Lifetime-rules: sem_undo is rcu-protected, on success, the function
|
|
* performs a rcu_read_lock().
|
|
*/
|
|
static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
|
|
{
|
|
struct sem_array *sma;
|
|
struct sem_undo_list *ulp;
|
|
struct sem_undo *un, *new;
|
|
int nsems;
|
|
int error;
|
|
|
|
error = get_undo_list(&ulp);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
|
|
rcu_read_lock();
|
|
spin_lock(&ulp->lock);
|
|
un = lookup_undo(ulp, semid);
|
|
spin_unlock(&ulp->lock);
|
|
if (likely(un!=NULL))
|
|
goto out;
|
|
rcu_read_unlock();
|
|
|
|
/* no undo structure around - allocate one. */
|
|
/* step 1: figure out the size of the semaphore array */
|
|
sma = sem_lock_check(ns, semid);
|
|
if (IS_ERR(sma))
|
|
return ERR_CAST(sma);
|
|
|
|
nsems = sma->sem_nsems;
|
|
sem_getref_and_unlock(sma);
|
|
|
|
/* step 2: allocate new undo structure */
|
|
new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
|
|
if (!new) {
|
|
sem_putref(sma);
|
|
return ERR_PTR(-ENOMEM);
|
|
}
|
|
|
|
/* step 3: Acquire the lock on semaphore array */
|
|
sem_lock_and_putref(sma);
|
|
if (sma->sem_perm.deleted) {
|
|
sem_unlock(sma);
|
|
kfree(new);
|
|
un = ERR_PTR(-EIDRM);
|
|
goto out;
|
|
}
|
|
spin_lock(&ulp->lock);
|
|
|
|
/*
|
|
* step 4: check for races: did someone else allocate the undo struct?
|
|
*/
|
|
un = lookup_undo(ulp, semid);
|
|
if (un) {
|
|
kfree(new);
|
|
goto success;
|
|
}
|
|
/* step 5: initialize & link new undo structure */
|
|
new->semadj = (short *) &new[1];
|
|
new->ulp = ulp;
|
|
new->semid = semid;
|
|
assert_spin_locked(&ulp->lock);
|
|
list_add_rcu(&new->list_proc, &ulp->list_proc);
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_add(&new->list_id, &sma->list_id);
|
|
un = new;
|
|
|
|
success:
|
|
spin_unlock(&ulp->lock);
|
|
rcu_read_lock();
|
|
sem_unlock(sma);
|
|
out:
|
|
return un;
|
|
}
|
|
|
|
|
|
/**
|
|
* get_queue_result - Retrieve the result code from sem_queue
|
|
* @q: Pointer to queue structure
|
|
*
|
|
* Retrieve the return code from the pending queue. If IN_WAKEUP is found in
|
|
* q->status, then we must loop until the value is replaced with the final
|
|
* value: This may happen if a task is woken up by an unrelated event (e.g.
|
|
* signal) and in parallel the task is woken up by another task because it got
|
|
* the requested semaphores.
|
|
*
|
|
* The function can be called with or without holding the semaphore spinlock.
|
|
*/
|
|
static int get_queue_result(struct sem_queue *q)
|
|
{
|
|
int error;
|
|
|
|
error = q->status;
|
|
while (unlikely(error == IN_WAKEUP)) {
|
|
cpu_relax();
|
|
error = q->status;
|
|
}
|
|
|
|
return error;
|
|
}
|
|
|
|
|
|
SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
|
|
unsigned, nsops, const struct timespec __user *, timeout)
|
|
{
|
|
int error = -EINVAL;
|
|
struct sem_array *sma;
|
|
struct sembuf fast_sops[SEMOPM_FAST];
|
|
struct sembuf* sops = fast_sops, *sop;
|
|
struct sem_undo *un;
|
|
int undos = 0, alter = 0, max;
|
|
struct sem_queue queue;
|
|
unsigned long jiffies_left = 0;
|
|
struct ipc_namespace *ns;
|
|
struct list_head tasks;
|
|
|
|
ns = current->nsproxy->ipc_ns;
|
|
|
|
if (nsops < 1 || semid < 0)
|
|
return -EINVAL;
|
|
if (nsops > ns->sc_semopm)
|
|
return -E2BIG;
|
|
if(nsops > SEMOPM_FAST) {
|
|
sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
|
|
if(sops==NULL)
|
|
return -ENOMEM;
|
|
}
|
|
if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
|
|
error=-EFAULT;
|
|
goto out_free;
|
|
}
|
|
if (timeout) {
|
|
struct timespec _timeout;
|
|
if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
|
|
error = -EFAULT;
|
|
goto out_free;
|
|
}
|
|
if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
|
|
_timeout.tv_nsec >= 1000000000L) {
|
|
error = -EINVAL;
|
|
goto out_free;
|
|
}
|
|
jiffies_left = timespec_to_jiffies(&_timeout);
|
|
}
|
|
max = 0;
|
|
for (sop = sops; sop < sops + nsops; sop++) {
|
|
if (sop->sem_num >= max)
|
|
max = sop->sem_num;
|
|
if (sop->sem_flg & SEM_UNDO)
|
|
undos = 1;
|
|
if (sop->sem_op != 0)
|
|
alter = 1;
|
|
}
|
|
|
|
if (undos) {
|
|
un = find_alloc_undo(ns, semid);
|
|
if (IS_ERR(un)) {
|
|
error = PTR_ERR(un);
|
|
goto out_free;
|
|
}
|
|
} else
|
|
un = NULL;
|
|
|
|
INIT_LIST_HEAD(&tasks);
|
|
|
|
sma = sem_lock_check(ns, semid);
|
|
if (IS_ERR(sma)) {
|
|
if (un)
|
|
rcu_read_unlock();
|
|
error = PTR_ERR(sma);
|
|
goto out_free;
|
|
}
|
|
|
|
/*
|
|
* semid identifiers are not unique - find_alloc_undo may have
|
|
* allocated an undo structure, it was invalidated by an RMID
|
|
* and now a new array with received the same id. Check and fail.
|
|
* This case can be detected checking un->semid. The existence of
|
|
* "un" itself is guaranteed by rcu.
|
|
*/
|
|
error = -EIDRM;
|
|
if (un) {
|
|
if (un->semid == -1) {
|
|
rcu_read_unlock();
|
|
goto out_unlock_free;
|
|
} else {
|
|
/*
|
|
* rcu lock can be released, "un" cannot disappear:
|
|
* - sem_lock is acquired, thus IPC_RMID is
|
|
* impossible.
|
|
* - exit_sem is impossible, it always operates on
|
|
* current (or a dead task).
|
|
*/
|
|
|
|
rcu_read_unlock();
|
|
}
|
|
}
|
|
|
|
error = -EFBIG;
|
|
if (max >= sma->sem_nsems)
|
|
goto out_unlock_free;
|
|
|
|
error = -EACCES;
|
|
if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
|
|
goto out_unlock_free;
|
|
|
|
error = security_sem_semop(sma, sops, nsops, alter);
|
|
if (error)
|
|
goto out_unlock_free;
|
|
|
|
error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
|
|
if (error <= 0) {
|
|
if (alter && error == 0)
|
|
do_smart_update(sma, sops, nsops, 1, &tasks);
|
|
|
|
goto out_unlock_free;
|
|
}
|
|
|
|
/* We need to sleep on this operation, so we put the current
|
|
* task into the pending queue and go to sleep.
|
|
*/
|
|
|
|
queue.sops = sops;
|
|
queue.nsops = nsops;
|
|
queue.undo = un;
|
|
queue.pid = task_tgid_vnr(current);
|
|
queue.alter = alter;
|
|
if (alter)
|
|
list_add_tail(&queue.list, &sma->sem_pending);
|
|
else
|
|
list_add(&queue.list, &sma->sem_pending);
|
|
|
|
if (nsops == 1) {
|
|
struct sem *curr;
|
|
curr = &sma->sem_base[sops->sem_num];
|
|
|
|
if (alter)
|
|
list_add_tail(&queue.simple_list, &curr->sem_pending);
|
|
else
|
|
list_add(&queue.simple_list, &curr->sem_pending);
|
|
} else {
|
|
INIT_LIST_HEAD(&queue.simple_list);
|
|
sma->complex_count++;
|
|
}
|
|
|
|
queue.status = -EINTR;
|
|
queue.sleeper = current;
|
|
|
|
sleep_again:
|
|
current->state = TASK_INTERRUPTIBLE;
|
|
sem_unlock(sma);
|
|
|
|
if (timeout)
|
|
jiffies_left = schedule_timeout(jiffies_left);
|
|
else
|
|
schedule();
|
|
|
|
error = get_queue_result(&queue);
|
|
|
|
if (error != -EINTR) {
|
|
/* fast path: update_queue already obtained all requested
|
|
* resources.
|
|
* Perform a smp_mb(): User space could assume that semop()
|
|
* is a memory barrier: Without the mb(), the cpu could
|
|
* speculatively read in user space stale data that was
|
|
* overwritten by the previous owner of the semaphore.
|
|
*/
|
|
smp_mb();
|
|
|
|
goto out_free;
|
|
}
|
|
|
|
sma = sem_lock(ns, semid);
|
|
|
|
/*
|
|
* Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
|
|
*/
|
|
error = get_queue_result(&queue);
|
|
|
|
/*
|
|
* Array removed? If yes, leave without sem_unlock().
|
|
*/
|
|
if (IS_ERR(sma)) {
|
|
goto out_free;
|
|
}
|
|
|
|
|
|
/*
|
|
* If queue.status != -EINTR we are woken up by another process.
|
|
* Leave without unlink_queue(), but with sem_unlock().
|
|
*/
|
|
|
|
if (error != -EINTR) {
|
|
goto out_unlock_free;
|
|
}
|
|
|
|
/*
|
|
* If an interrupt occurred we have to clean up the queue
|
|
*/
|
|
if (timeout && jiffies_left == 0)
|
|
error = -EAGAIN;
|
|
|
|
/*
|
|
* If the wakeup was spurious, just retry
|
|
*/
|
|
if (error == -EINTR && !signal_pending(current))
|
|
goto sleep_again;
|
|
|
|
unlink_queue(sma, &queue);
|
|
|
|
out_unlock_free:
|
|
sem_unlock(sma);
|
|
|
|
wake_up_sem_queue_do(&tasks);
|
|
out_free:
|
|
if(sops != fast_sops)
|
|
kfree(sops);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
|
|
unsigned, nsops)
|
|
{
|
|
return sys_semtimedop(semid, tsops, nsops, NULL);
|
|
}
|
|
|
|
/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
|
|
* parent and child tasks.
|
|
*/
|
|
|
|
int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
|
|
{
|
|
struct sem_undo_list *undo_list;
|
|
int error;
|
|
|
|
if (clone_flags & CLONE_SYSVSEM) {
|
|
error = get_undo_list(&undo_list);
|
|
if (error)
|
|
return error;
|
|
atomic_inc(&undo_list->refcnt);
|
|
tsk->sysvsem.undo_list = undo_list;
|
|
} else
|
|
tsk->sysvsem.undo_list = NULL;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* add semadj values to semaphores, free undo structures.
|
|
* undo structures are not freed when semaphore arrays are destroyed
|
|
* so some of them may be out of date.
|
|
* IMPLEMENTATION NOTE: There is some confusion over whether the
|
|
* set of adjustments that needs to be done should be done in an atomic
|
|
* manner or not. 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 (queue and wait).
|
|
* The current implementation does not do so. The POSIX standard
|
|
* and SVID should be consulted to determine what behavior is mandated.
|
|
*/
|
|
void exit_sem(struct task_struct *tsk)
|
|
{
|
|
struct sem_undo_list *ulp;
|
|
|
|
ulp = tsk->sysvsem.undo_list;
|
|
if (!ulp)
|
|
return;
|
|
tsk->sysvsem.undo_list = NULL;
|
|
|
|
if (!atomic_dec_and_test(&ulp->refcnt))
|
|
return;
|
|
|
|
for (;;) {
|
|
struct sem_array *sma;
|
|
struct sem_undo *un;
|
|
struct list_head tasks;
|
|
int semid;
|
|
int i;
|
|
|
|
rcu_read_lock();
|
|
un = list_entry_rcu(ulp->list_proc.next,
|
|
struct sem_undo, list_proc);
|
|
if (&un->list_proc == &ulp->list_proc)
|
|
semid = -1;
|
|
else
|
|
semid = un->semid;
|
|
rcu_read_unlock();
|
|
|
|
if (semid == -1)
|
|
break;
|
|
|
|
sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid);
|
|
|
|
/* exit_sem raced with IPC_RMID, nothing to do */
|
|
if (IS_ERR(sma))
|
|
continue;
|
|
|
|
un = __lookup_undo(ulp, semid);
|
|
if (un == NULL) {
|
|
/* exit_sem raced with IPC_RMID+semget() that created
|
|
* exactly the same semid. Nothing to do.
|
|
*/
|
|
sem_unlock(sma);
|
|
continue;
|
|
}
|
|
|
|
/* remove un from the linked lists */
|
|
assert_spin_locked(&sma->sem_perm.lock);
|
|
list_del(&un->list_id);
|
|
|
|
spin_lock(&ulp->lock);
|
|
list_del_rcu(&un->list_proc);
|
|
spin_unlock(&ulp->lock);
|
|
|
|
/* perform adjustments registered in un */
|
|
for (i = 0; i < sma->sem_nsems; i++) {
|
|
struct sem * semaphore = &sma->sem_base[i];
|
|
if (un->semadj[i]) {
|
|
semaphore->semval += un->semadj[i];
|
|
/*
|
|
* Range checks of the new semaphore value,
|
|
* not defined by sus:
|
|
* - Some unices ignore the undo entirely
|
|
* (e.g. HP UX 11i 11.22, Tru64 V5.1)
|
|
* - some cap the value (e.g. FreeBSD caps
|
|
* at 0, but doesn't enforce SEMVMX)
|
|
*
|
|
* Linux caps the semaphore value, both at 0
|
|
* and at SEMVMX.
|
|
*
|
|
* Manfred <manfred@colorfullife.com>
|
|
*/
|
|
if (semaphore->semval < 0)
|
|
semaphore->semval = 0;
|
|
if (semaphore->semval > SEMVMX)
|
|
semaphore->semval = SEMVMX;
|
|
semaphore->sempid = task_tgid_vnr(current);
|
|
}
|
|
}
|
|
/* maybe some queued-up processes were waiting for this */
|
|
INIT_LIST_HEAD(&tasks);
|
|
do_smart_update(sma, NULL, 0, 1, &tasks);
|
|
sem_unlock(sma);
|
|
wake_up_sem_queue_do(&tasks);
|
|
|
|
kfree_rcu(un, rcu);
|
|
}
|
|
kfree(ulp);
|
|
}
|
|
|
|
#ifdef CONFIG_PROC_FS
|
|
static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
|
|
{
|
|
struct user_namespace *user_ns = seq_user_ns(s);
|
|
struct sem_array *sma = it;
|
|
|
|
return seq_printf(s,
|
|
"%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
|
|
sma->sem_perm.key,
|
|
sma->sem_perm.id,
|
|
sma->sem_perm.mode,
|
|
sma->sem_nsems,
|
|
from_kuid_munged(user_ns, sma->sem_perm.uid),
|
|
from_kgid_munged(user_ns, sma->sem_perm.gid),
|
|
from_kuid_munged(user_ns, sma->sem_perm.cuid),
|
|
from_kgid_munged(user_ns, sma->sem_perm.cgid),
|
|
sma->sem_otime,
|
|
sma->sem_ctime);
|
|
}
|
|
#endif
|