linux/fs/autofs4/waitq.c
Ian Kent cc9acc8858 [PATCH] autofs4: post expire race fix
At the tail end of an expire it's possible for a process to enter
autofs4_wait, with a waitq type of NFY_NONE but find that the expire is
finished.  In this cause autofs4_wait will try to create a new wait but not
notify the daemon leading to a hang.  As the wait type is meant to delay mount
requests from revalidate or lookup during an expire and the expire is done all
we need to do is check if the dentry is a mountpoint.  If it's not then we're
done.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-21 19:07:35 -07:00

313 lines
7.7 KiB
C

/* -*- c -*- --------------------------------------------------------------- *
*
* linux/fs/autofs/waitq.c
*
* Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
* Copyright 2001-2003 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;
if (type == 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';
} else if (type == 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';
} else {
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;
}
int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
enum autofs_notify notify)
{
struct autofs_wait_queue *wq;
char *name;
int len, status;
/* 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;
len = autofs4_getpath(sbi, dentry, &name);
if (!len) {
kfree(name);
return -ENOENT;
}
if (down_interruptible(&sbi->wq_sem)) {
kfree(name);
return -EINTR;
}
for (wq = sbi->queues ; wq ; wq = wq->next) {
if (wq->hash == dentry->d_name.hash &&
wq->len == len &&
wq->name && !memcmp(wq->name, name, len))
break;
}
if ( !wq ) {
/* Can't wait for an expire if there's no mount */
if (notify == NFY_NONE && !d_mountpoint(dentry)) {
kfree(name);
up(&sbi->wq_sem);
return -ENOENT;
}
/* Create a new wait queue */
wq = kmalloc(sizeof(struct autofs_wait_queue),GFP_KERNEL);
if ( !wq ) {
kfree(name);
up(&sbi->wq_sem);
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 = dentry->d_name.hash;
wq->name = name;
wq->len = len;
wq->status = -EINTR; /* Status return if interrupted */
atomic_set(&wq->wait_ctr, 2);
atomic_set(&wq->notified, 1);
up(&sbi->wq_sem);
} else {
atomic_inc(&wq->wait_ctr);
up(&sbi->wq_sem);
kfree(name);
DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
(unsigned long) wq->wait_queue_token, wq->len, wq->name, notify);
}
if (notify != NFY_NONE && atomic_dec_and_test(&wq->notified)) {
int type = (notify == NFY_MOUNT ?
autofs_ptype_missing : autofs_ptype_expire_multi);
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);
}
/* 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;
if ( wq->name ) {
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;
down(&sbi->wq_sem);
for ( wql = &sbi->queues ; (wq = *wql) != 0 ; wql = &wq->next ) {
if ( wq->wait_queue_token == wait_queue_token )
break;
}
if ( !wq ) {
up(&sbi->wq_sem);
return -EINVAL;
}
*wql = wq->next; /* Unlink from chain */
up(&sbi->wq_sem);
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;
}