linux/ipc/sem.c

1416 lines
35 KiB
C
Raw Normal View History

/*
* 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 <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 <alan@redhat.com>
* Lockless wakeup
* (c) 2003 Manfred Spraul <manfred@colorfullife.com>
[PATCH] Rework of IPC auditing 1) The audit_ipc_perms() function has been split into two different functions: - audit_ipc_obj() - audit_ipc_set_perm() There's a key shift here... The audit_ipc_obj() collects the uid, gid, mode, and SElinux context label of the current ipc object. This audit_ipc_obj() hook is now found in several places. Most notably, it is hooked in ipcperms(), which is called in various places around the ipc code permforming a MAC check. Additionally there are several places where *checkid() is used to validate that an operation is being performed on a valid object while not necessarily having a nearby ipcperms() call. In these locations, audit_ipc_obj() is called to ensure that the information is captured by the audit system. The audit_set_new_perm() function is called any time the permissions on the ipc object changes. In this case, the NEW permissions are recorded (and note that an audit_ipc_obj() call exists just a few lines before each instance). 2) Support for an AUDIT_IPC_SET_PERM audit message type. This allows for separate auxiliary audit records for normal operations on an IPC object and permissions changes. Note that the same struct audit_aux_data_ipcctl is used and populated, however there are separate audit_log_format statements based on the type of the message. Finally, the AUDIT_IPC block of code in audit_free_aux() was extended to handle aux messages of this new type. No more mem leaks I hope ;-) Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2006-04-02 23:07:33 +02:00
*
* 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>
*/
#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/mutex.h>
#include <linux/nsproxy.h>
#include <asm/uaccess.h>
#include "util.h"
#define sem_ids(ns) (*((ns)->ids[IPC_SEM_IDS]))
#define sem_lock(ns, id) ((struct sem_array*)ipc_lock(&sem_ids(ns), id))
#define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
#define sem_rmid(ns, id) ((struct sem_array*)ipc_rmid(&sem_ids(ns), id))
#define sem_checkid(ns, sma, semid) \
ipc_checkid(&sem_ids(ns),&sma->sem_perm,semid)
#define sem_buildid(ns, id, seq) \
ipc_buildid(&sem_ids(ns), id, seq)
static struct ipc_ids init_sem_ids;
static int newary(struct ipc_namespace *, key_t, int, int);
static void freeary(struct ipc_namespace *ns, struct sem_array *sma, int id);
#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, ns->sc_semmni);
}
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)
{
int i;
struct sem_array *sma;
mutex_lock(&sem_ids(ns).mutex);
for (i = 0; i <= sem_ids(ns).max_id; i++) {
sma = sem_lock(ns, i);
if (sma == NULL)
continue;
freeary(ns, sma, i);
}
mutex_unlock(&sem_ids(ns).mutex);
ipc_fini_ids(ns->ids[IPC_SEM_IDS]);
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);
}
/*
* 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
static int newary (struct ipc_namespace *ns, key_t key, int nsems, int semflg)
{
int id;
int retval;
struct sem_array *sma;
int size;
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 == -1) {
security_sem_free(sma);
ipc_rcu_putref(sma);
return -ENOSPC;
}
ns->used_sems += nsems;
sma->sem_id = sem_buildid(ns, 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_id;
}
asmlinkage long sys_semget (key_t key, int nsems, int semflg)
{
int id, err = -EINVAL;
struct sem_array *sma;
struct ipc_namespace *ns;
ns = current->nsproxy->ipc_ns;
if (nsems < 0 || nsems > ns->sc_semmsl)
return -EINVAL;
mutex_lock(&sem_ids(ns).mutex);
if (key == IPC_PRIVATE) {
err = newary(ns, key, nsems, semflg);
} else if ((id = ipc_findkey(&sem_ids(ns), key)) == -1) { /* key not used */
if (!(semflg & IPC_CREAT))
err = -ENOENT;
else
err = newary(ns, key, nsems, semflg);
} else if (semflg & IPC_CREAT && semflg & IPC_EXCL) {
err = -EEXIST;
} else {
sma = sem_lock(ns, id);
BUG_ON(sma==NULL);
if (nsems > sma->sem_nsems)
err = -EINVAL;
else if (ipcperms(&sma->sem_perm, semflg))
err = -EACCES;
else {
int semid = sem_buildid(ns, id, sma->sem_perm.seq);
err = security_sem_associate(sma, semflg);
if (!err)
err = semid;
}
sem_unlock(sma);
}
mutex_unlock(&sem_ids(ns).mutex);
return err;
}
/* 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.mutex locked and
* the spinlock for this semaphore set hold. sem_ids.mutex remains locked
* on exit.
*/
static void freeary (struct ipc_namespace *ns, struct sem_array *sma, int id)
{
struct sem_undo *un;
struct sem_queue *q;
int size;
/* 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 ID array*/
sma = sem_rmid(ns, id);
sem_unlock(sma);
ns->used_sems -= sma->sem_nsems;
size = sizeof (*sma) + sma->sem_nsems * sizeof (struct sem);
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;
mutex_lock(&sem_ids(ns).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 = sem_ids(ns).max_id;
mutex_unlock(&sem_ids(ns).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;
if(semid >= sem_ids(ns).entries->size)
return -EINVAL;
memset(&tbuf,0,sizeof(tbuf));
sma = sem_lock(ns, semid);
if(sma == NULL)
return -EINVAL;
err = -EACCES;
if (ipcperms (&sma->sem_perm, S_IRUGO))
goto out_unlock;
err = security_sem_semctl(sma, cmd);
if (err)
goto out_unlock;
id = sem_buildid(ns, semid, sma->sem_perm.seq);
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(ns, semid);
if(sma==NULL)
return -EINVAL;
nsems = sma->sem_nsems;
err=-EIDRM;
if (sem_checkid(ns,sma,semid))
goto out_unlock;
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 = current->tgid;
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(ns, semid);
if(sma==NULL)
return -EINVAL;
if (sem_checkid(ns,sma,semid)) {
err=-EIDRM;
goto out_unlock;
}
ipcp = &sma->sem_perm;
[PATCH] Rework of IPC auditing 1) The audit_ipc_perms() function has been split into two different functions: - audit_ipc_obj() - audit_ipc_set_perm() There's a key shift here... The audit_ipc_obj() collects the uid, gid, mode, and SElinux context label of the current ipc object. This audit_ipc_obj() hook is now found in several places. Most notably, it is hooked in ipcperms(), which is called in various places around the ipc code permforming a MAC check. Additionally there are several places where *checkid() is used to validate that an operation is being performed on a valid object while not necessarily having a nearby ipcperms() call. In these locations, audit_ipc_obj() is called to ensure that the information is captured by the audit system. The audit_set_new_perm() function is called any time the permissions on the ipc object changes. In this case, the NEW permissions are recorded (and note that an audit_ipc_obj() call exists just a few lines before each instance). 2) Support for an AUDIT_IPC_SET_PERM audit message type. This allows for separate auxiliary audit records for normal operations on an IPC object and permissions changes. Note that the same struct audit_aux_data_ipcctl is used and populated, however there are separate audit_log_format statements based on the type of the message. Finally, the AUDIT_IPC block of code in audit_free_aux() was extended to handle aux messages of this new type. No more mem leaks I hope ;-) Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2006-04-02 23:07:33 +02:00
err = audit_ipc_obj(ipcp);
if (err)
goto out_unlock;
[PATCH] update of IPC audit record cleanup The following patch addresses most of the issues with the IPC_SET_PERM records as described in: https://www.redhat.com/archives/linux-audit/2006-May/msg00010.html and addresses the comments I received on the record field names. To summarize, I made the following changes: 1. Changed sys_msgctl() and semctl_down() so that an IPC_SET_PERM record is emitted in the failure case as well as the success case. This matches the behavior in sys_shmctl(). I could simplify the code in sys_msgctl() and semctl_down() slightly but it would mean that in some error cases we could get an IPC_SET_PERM record without an IPC record and that seemed odd. 2. No change to the IPC record type, given no feedback on the backward compatibility question. 3. Removed the qbytes field from the IPC record. It wasn't being set and when audit_ipc_obj() is called from ipcperms(), the information isn't available. If we want the information in the IPC record, more extensive changes will be necessary. Since it only applies to message queues and it isn't really permission related, it doesn't seem worth it. 4. Removed the obj field from the IPC_SET_PERM record. This means that the kern_ipc_perm argument is no longer needed. 5. Removed the spaces and renamed the IPC_SET_PERM field names. Replaced iuid and igid fields with ouid and ogid in the IPC record. I tested this with the lspp.22 kernel on an x86_64 box. I believe it applies cleanly on the latest kernel. -- ljk Signed-off-by: Linda Knippers <linda.knippers@hp.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2006-05-17 04:03:48 +02:00
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, semid);
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:
mutex_lock(&sem_ids(ns).mutex);
err = semctl_down(ns,semid,semnum,cmd,version,arg);
mutex_unlock(&sem_ids(ns).mutex);
return err;
default:
return -EINVAL;
}
}
static inline void lock_semundo(void)
{
struct sem_undo_list *undo_list;
undo_list = current->sysvsem.undo_list;
if (undo_list)
spin_lock(&undo_list->lock);
}
/* This code has an interaction with copy_semundo().
* Consider; two tasks are sharing the undo_list. task1
* acquires the undo_list lock in lock_semundo(). If task2 now
* exits before task1 releases the lock (by calling
* unlock_semundo()), then task1 will never call spin_unlock().
* This leave the sem_undo_list in a locked state. If task1 now creats task3
* and once again shares the sem_undo_list, the sem_undo_list will still be
* locked, and future SEM_UNDO operations will deadlock. This case is
* dealt with in copy_semundo() by having it reinitialize the spin lock when
* the refcnt goes from 1 to 2.
*/
static inline void unlock_semundo(void)
{
struct sem_undo_list *undo_list;
undo_list = current->sysvsem.undo_list;
if (undo_list)
spin_unlock(&undo_list->lock);
}
/* 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);
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 **last, *un;
last = &ulp->proc_list;
un = *last;
while(un != NULL) {
if(un->semid==semid)
break;
if(un->semid==-1) {
*last=un->proc_next;
kfree(un);
} else {
last=&un->proc_next;
}
un=*last;
}
return un;
}
static struct sem_undo *find_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);
lock_semundo();
un = lookup_undo(ulp, semid);
unlock_semundo();
if (likely(un!=NULL))
goto out;
/* no undo structure around - allocate one. */
sma = sem_lock(ns, semid);
un = ERR_PTR(-EINVAL);
if(sma==NULL)
goto out;
un = ERR_PTR(-EIDRM);
if (sem_checkid(ns,sma,semid)) {
sem_unlock(sma);
goto out;
}
nsems = sma->sem_nsems;
ipc_rcu_getref(sma);
sem_unlock(sma);
new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
if (!new) {
ipc_lock_by_ptr(&sma->sem_perm);
ipc_rcu_putref(sma);
sem_unlock(sma);
return ERR_PTR(-ENOMEM);
}
new->semadj = (short *) &new[1];
new->semid = semid;
lock_semundo();
un = lookup_undo(ulp, semid);
if (un) {
unlock_semundo();
kfree(new);
ipc_lock_by_ptr(&sma->sem_perm);
ipc_rcu_putref(sma);
sem_unlock(sma);
goto out;
}
ipc_lock_by_ptr(&sma->sem_perm);
ipc_rcu_putref(sma);
if (sma->sem_perm.deleted) {
sem_unlock(sma);
unlock_semundo();
kfree(new);
un = ERR_PTR(-EIDRM);
goto out;
}
new->proc_next = ulp->proc_list;
ulp->proc_list = new;
new->id_next = sma->undo;
sma->undo = new;
sem_unlock(sma);
un = new;
unlock_semundo();
out:
return un;
}
asmlinkage long sys_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;
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;
}
retry_undos:
if (undos) {
un = find_undo(ns, semid);
if (IS_ERR(un)) {
error = PTR_ERR(un);
goto out_free;
}
} else
un = NULL;
sma = sem_lock(ns, semid);
error=-EINVAL;
if(sma==NULL)
goto out_free;
error = -EIDRM;
if (sem_checkid(ns,sma,semid))
goto out_unlock_free;
/*
* semid identifies are not unique - find_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 retry.
*/
if (un && un->semid == -1) {
sem_unlock(sma);
goto retry_undos;
}
error = -EFBIG;
if (max >= sma->sem_nsems)
goto out_unlock_free;
error = -EACCES;
if (ipcperms(&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, current->tgid);
if (error <= 0) {
if (alter && error == 0)
update_queue (sma);
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.sma = sma;
queue.sops = sops;
queue.nsops = nsops;
queue.undo = un;
queue.pid = current->tgid;
queue.id = semid;
queue.alter = alter;
if (alter)
append_to_queue(sma ,&queue);
else
prepend_to_queue(sma ,&queue);
queue.status = -EINTR;
queue.sleeper = current;
current->state = TASK_INTERRUPTIBLE;
sem_unlock(sma);
if (timeout)
jiffies_left = schedule_timeout(jiffies_left);
else
schedule();
error = queue.status;
while(unlikely(error == IN_WAKEUP)) {
cpu_relax();
error = queue.status;
}
if (error != -EINTR) {
/* fast path: update_queue already obtained all requested
* resources */
goto out_free;
}
sma = sem_lock(ns, semid);
if(sma==NULL) {
BUG_ON(queue.prev != NULL);
error = -EIDRM;
goto out_free;
}
/*
* If queue.status != -EINTR we are woken up by another process
*/
error = queue.status;
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;
remove_from_queue(sma,&queue);
goto out_unlock_free;
out_unlock_free:
sem_unlock(sma);
out_free:
if(sops != fast_sops)
kfree(sops);
return error;
}
asmlinkage long sys_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.
*
* See the notes above unlock_semundo() regarding the spin_lock_init()
* in this code. Initialize the undo_list->lock here instead of get_undo_list()
* because of the reasoning in the comment above unlock_semundo.
*/
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 *undo_list;
struct sem_undo *u, **up;
struct ipc_namespace *ns;
undo_list = tsk->sysvsem.undo_list;
if (!undo_list)
return;
if (!atomic_dec_and_test(&undo_list->refcnt))
return;
ns = tsk->nsproxy->ipc_ns;
/* There's no need to hold the semundo list lock, as current
* is the last task exiting for this undo list.
*/
for (up = &undo_list->proc_list; (u = *up); *up = u->proc_next, kfree(u)) {
struct sem_array *sma;
int nsems, i;
struct sem_undo *un, **unp;
int semid;
semid = u->semid;
if(semid == -1)
continue;
sma = sem_lock(ns, semid);
if (sma == NULL)
continue;
if (u->semid == -1)
goto next_entry;
BUG_ON(sem_checkid(ns,sma,u->semid));
/* remove u from the sma->undo list */
for (unp = &sma->undo; (un = *unp); unp = &un->id_next) {
if (u == un)
goto found;
}
printk ("exit_sem undo list error id=%d\n", u->semid);
goto next_entry;
found:
*unp = un->id_next;
/* perform adjustments registered in u */
nsems = sma->sem_nsems;
for (i = 0; i < nsems; i++) {
struct sem * semaphore = &sma->sem_base[i];
if (u->semadj[i]) {
semaphore->semval += u->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 = current->tgid;
}
}
sma->sem_otime = get_seconds();
/* maybe some queued-up processes were waiting for this */
update_queue(sma);
next_entry:
sem_unlock(sma);
}
kfree(undo_list);
}
#ifdef CONFIG_PROC_FS
static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
{
struct sem_array *sma = it;
return seq_printf(s,
"%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",
sma->sem_perm.key,
sma->sem_id,
sma->sem_perm.mode,
sma->sem_nsems,
sma->sem_perm.uid,
sma->sem_perm.gid,
sma->sem_perm.cuid,
sma->sem_perm.cgid,
sma->sem_otime,
sma->sem_ctime);
}
#endif