android_kernel_xiaomi_sm8350/fs/autofs4/waitq.c
Ian Kent 3e7b191980 [PATCH] autofs4: atomic var underflow
Fix accidental underflow of the atomic counter.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-27 08:44:41 -08:00

374 lines
9.2 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;
}
int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
enum autofs_notify notify)
{
struct autofs_wait_queue *wq;
char *name;
unsigned int len = 0;
unsigned int hash = 0;
int 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;
/* 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;
}
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);
mutex_unlock(&sbi->wq_mutex);
return -ENOENT;
}
/* 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);
atomic_set(&wq->notify, 1);
mutex_unlock(&sbi->wq_mutex);
} 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);
}
if (notify != NFY_NONE && atomic_read(&wq->notify)) {
int type;
atomic_dec(&wq->notify);
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);
}
/* 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;
}