linux/fs/autofs4/waitq.c
Ian Kent a537055395 [PATCH] autofs4: NFY_NONE wait race fix
This patch fixes two problems.

First, the comparison of entries in the waitq.c was incorrect.

Second, the NFY_NONE check was incorrect. The test of whether the dentry
is mounted if ineffective, for example, if an expire fails then we could
wait forever on a non existant expire. The bug was identified by Jeff
Moyer.

The patch changes autofs4 to wait on expires only as this is all that's
needed.  If there is no existing wait when autofs4_wait is call with a type
of NFY_NONE it delays until either a wait appears or the the expire flag is
cleared.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-05-15 11:20:54 -07:00

402 lines
9.9 KiB
C

/* -*- c -*- --------------------------------------------------------------- *
*
* linux/fs/autofs/waitq.c
*
* Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
* Copyright 2001-2006 Ian Kent <raven@themaw.net>
*
* This file is part of the Linux kernel and is made available under
* the terms of the GNU General Public License, version 2, or at your
* option, any later version, incorporated herein by reference.
*
* ------------------------------------------------------------------------- */
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/signal.h>
#include <linux/file.h>
#include "autofs_i.h"
/* We make this a static variable rather than a part of the superblock; it
is better if we don't reassign numbers easily even across filesystems */
static autofs_wqt_t autofs4_next_wait_queue = 1;
/* These are the signals we allow interrupting a pending mount */
#define SHUTDOWN_SIGS (sigmask(SIGKILL) | sigmask(SIGINT) | sigmask(SIGQUIT))
void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
{
struct autofs_wait_queue *wq, *nwq;
DPRINTK("entering catatonic mode");
sbi->catatonic = 1;
wq = sbi->queues;
sbi->queues = NULL; /* Erase all wait queues */
while (wq) {
nwq = wq->next;
wq->status = -ENOENT; /* Magic is gone - report failure */
kfree(wq->name);
wq->name = NULL;
wake_up_interruptible(&wq->queue);
wq = nwq;
}
if (sbi->pipe) {
fput(sbi->pipe); /* Close the pipe */
sbi->pipe = NULL;
}
shrink_dcache_sb(sbi->sb);
}
static int autofs4_write(struct file *file, const void *addr, int bytes)
{
unsigned long sigpipe, flags;
mm_segment_t fs;
const char *data = (const char *)addr;
ssize_t wr = 0;
/** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/
sigpipe = sigismember(&current->pending.signal, SIGPIPE);
/* Save pointer to user space and point back to kernel space */
fs = get_fs();
set_fs(KERNEL_DS);
while (bytes &&
(wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {
data += wr;
bytes -= wr;
}
set_fs(fs);
/* Keep the currently executing process from receiving a
SIGPIPE unless it was already supposed to get one */
if (wr == -EPIPE && !sigpipe) {
spin_lock_irqsave(&current->sighand->siglock, flags);
sigdelset(&current->pending.signal, SIGPIPE);
recalc_sigpending();
spin_unlock_irqrestore(&current->sighand->siglock, flags);
}
return (bytes > 0);
}
static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
struct autofs_wait_queue *wq,
int type)
{
union autofs_packet_union pkt;
size_t pktsz;
DPRINTK("wait id = 0x%08lx, name = %.*s, type=%d",
wq->wait_queue_token, wq->len, wq->name, type);
memset(&pkt,0,sizeof pkt); /* For security reasons */
pkt.hdr.proto_version = sbi->version;
pkt.hdr.type = type;
switch (type) {
/* Kernel protocol v4 missing and expire packets */
case autofs_ptype_missing:
{
struct autofs_packet_missing *mp = &pkt.missing;
pktsz = sizeof(*mp);
mp->wait_queue_token = wq->wait_queue_token;
mp->len = wq->len;
memcpy(mp->name, wq->name, wq->len);
mp->name[wq->len] = '\0';
break;
}
case autofs_ptype_expire_multi:
{
struct autofs_packet_expire_multi *ep = &pkt.expire_multi;
pktsz = sizeof(*ep);
ep->wait_queue_token = wq->wait_queue_token;
ep->len = wq->len;
memcpy(ep->name, wq->name, wq->len);
ep->name[wq->len] = '\0';
break;
}
/*
* Kernel protocol v5 packet for handling indirect and direct
* mount missing and expire requests
*/
case autofs_ptype_missing_indirect:
case autofs_ptype_expire_indirect:
case autofs_ptype_missing_direct:
case autofs_ptype_expire_direct:
{
struct autofs_v5_packet *packet = &pkt.v5_packet;
pktsz = sizeof(*packet);
packet->wait_queue_token = wq->wait_queue_token;
packet->len = wq->len;
memcpy(packet->name, wq->name, wq->len);
packet->name[wq->len] = '\0';
packet->dev = wq->dev;
packet->ino = wq->ino;
packet->uid = wq->uid;
packet->gid = wq->gid;
packet->pid = wq->pid;
packet->tgid = wq->tgid;
break;
}
default:
printk("autofs4_notify_daemon: bad type %d!\n", type);
return;
}
if (autofs4_write(sbi->pipe, &pkt, pktsz))
autofs4_catatonic_mode(sbi);
}
static int autofs4_getpath(struct autofs_sb_info *sbi,
struct dentry *dentry, char **name)
{
struct dentry *root = sbi->sb->s_root;
struct dentry *tmp;
char *buf = *name;
char *p;
int len = 0;
spin_lock(&dcache_lock);
for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
len += tmp->d_name.len + 1;
if (--len > NAME_MAX) {
spin_unlock(&dcache_lock);
return 0;
}
*(buf + len) = '\0';
p = buf + len - dentry->d_name.len;
strncpy(p, dentry->d_name.name, dentry->d_name.len);
for (tmp = dentry->d_parent; tmp != root ; tmp = tmp->d_parent) {
*(--p) = '/';
p -= tmp->d_name.len;
strncpy(p, tmp->d_name.name, tmp->d_name.len);
}
spin_unlock(&dcache_lock);
return len;
}
static struct autofs_wait_queue *
autofs4_find_wait(struct autofs_sb_info *sbi,
char *name, unsigned int hash, unsigned int len)
{
struct autofs_wait_queue *wq;
for (wq = sbi->queues; wq; wq = wq->next) {
if (wq->hash == hash &&
wq->len == len &&
wq->name && !memcmp(wq->name, name, len))
break;
}
return wq;
}
int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
enum autofs_notify notify)
{
struct autofs_info *ino;
struct autofs_wait_queue *wq;
char *name;
unsigned int len = 0;
unsigned int hash = 0;
int status, type;
/* In catatonic mode, we don't wait for nobody */
if (sbi->catatonic)
return -ENOENT;
name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
if (!name)
return -ENOMEM;
/* If this is a direct mount request create a dummy name */
if (IS_ROOT(dentry) && (sbi->type & AUTOFS_TYPE_DIRECT))
len = sprintf(name, "%p", dentry);
else {
len = autofs4_getpath(sbi, dentry, &name);
if (!len) {
kfree(name);
return -ENOENT;
}
}
hash = full_name_hash(name, len);
if (mutex_lock_interruptible(&sbi->wq_mutex)) {
kfree(name);
return -EINTR;
}
wq = autofs4_find_wait(sbi, name, hash, len);
ino = autofs4_dentry_ino(dentry);
if (!wq && ino && notify == NFY_NONE) {
/*
* Either we've betean the pending expire to post it's
* wait or it finished while we waited on the mutex.
* So we need to wait till either, the wait appears
* or the expire finishes.
*/
while (ino->flags & AUTOFS_INF_EXPIRING) {
mutex_unlock(&sbi->wq_mutex);
schedule_timeout_interruptible(HZ/10);
if (mutex_lock_interruptible(&sbi->wq_mutex)) {
kfree(name);
return -EINTR;
}
wq = autofs4_find_wait(sbi, name, hash, len);
if (wq)
break;
}
/*
* Not ideal but the status has already gone. Of the two
* cases where we wait on NFY_NONE neither depend on the
* return status of the wait.
*/
if (!wq) {
kfree(name);
mutex_unlock(&sbi->wq_mutex);
return 0;
}
}
if (!wq) {
/* Create a new wait queue */
wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
if (!wq) {
kfree(name);
mutex_unlock(&sbi->wq_mutex);
return -ENOMEM;
}
wq->wait_queue_token = autofs4_next_wait_queue;
if (++autofs4_next_wait_queue == 0)
autofs4_next_wait_queue = 1;
wq->next = sbi->queues;
sbi->queues = wq;
init_waitqueue_head(&wq->queue);
wq->hash = hash;
wq->name = name;
wq->len = len;
wq->dev = autofs4_get_dev(sbi);
wq->ino = autofs4_get_ino(sbi);
wq->uid = current->uid;
wq->gid = current->gid;
wq->pid = current->pid;
wq->tgid = current->tgid;
wq->status = -EINTR; /* Status return if interrupted */
atomic_set(&wq->wait_ctr, 2);
mutex_unlock(&sbi->wq_mutex);
if (sbi->version < 5) {
if (notify == NFY_MOUNT)
type = autofs_ptype_missing;
else
type = autofs_ptype_expire_multi;
} else {
if (notify == NFY_MOUNT)
type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
autofs_ptype_missing_direct :
autofs_ptype_missing_indirect;
else
type = (sbi->type & AUTOFS_TYPE_DIRECT) ?
autofs_ptype_expire_direct :
autofs_ptype_expire_indirect;
}
DPRINTK("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
(unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
/* autofs4_notify_daemon() may block */
autofs4_notify_daemon(sbi, wq, type);
} else {
atomic_inc(&wq->wait_ctr);
mutex_unlock(&sbi->wq_mutex);
kfree(name);
DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
(unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
}
/* wq->name is NULL if and only if the lock is already released */
if (sbi->catatonic) {
/* We might have slept, so check again for catatonic mode */
wq->status = -ENOENT;
kfree(wq->name);
wq->name = NULL;
}
if (wq->name) {
/* Block all but "shutdown" signals while waiting */
sigset_t oldset;
unsigned long irqflags;
spin_lock_irqsave(&current->sighand->siglock, irqflags);
oldset = current->blocked;
siginitsetinv(&current->blocked, SHUTDOWN_SIGS & ~oldset.sig[0]);
recalc_sigpending();
spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
wait_event_interruptible(wq->queue, wq->name == NULL);
spin_lock_irqsave(&current->sighand->siglock, irqflags);
current->blocked = oldset;
recalc_sigpending();
spin_unlock_irqrestore(&current->sighand->siglock, irqflags);
} else {
DPRINTK("skipped sleeping");
}
status = wq->status;
/* Are we the last process to need status? */
if (atomic_dec_and_test(&wq->wait_ctr))
kfree(wq);
return status;
}
int autofs4_wait_release(struct autofs_sb_info *sbi, autofs_wqt_t wait_queue_token, int status)
{
struct autofs_wait_queue *wq, **wql;
mutex_lock(&sbi->wq_mutex);
for (wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next) {
if (wq->wait_queue_token == wait_queue_token)
break;
}
if (!wq) {
mutex_unlock(&sbi->wq_mutex);
return -EINVAL;
}
*wql = wq->next; /* Unlink from chain */
mutex_unlock(&sbi->wq_mutex);
kfree(wq->name);
wq->name = NULL; /* Do not wait on this queue */
wq->status = status;
if (atomic_dec_and_test(&wq->wait_ctr)) /* Is anyone still waiting for this guy? */
kfree(wq);
else
wake_up_interruptible(&wq->queue);
return 0;
}