linux/fs/autofs/waitq.c
Al Viro 2be7828c9f get rid of autofs_getpath()
allow wq->name.name to point not at the beginning of the object containing
the string, with wq->offset telling how far into it we are.  Then we can
bloody well just use dentry_path_raw() instead of autofs_getpath() -
the only real difference is that dentry_path_raw() puts the result into
the end of buffer and returns where it starts.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2021-03-21 11:44:02 -04:00

513 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright 1997-1998 Transmeta Corporation -- All Rights Reserved
* Copyright 2001-2006 Ian Kent <raven@themaw.net>
*/
#include <linux/sched/signal.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 autofs_next_wait_queue = 1;
void autofs_catatonic_mode(struct autofs_sb_info *sbi)
{
struct autofs_wait_queue *wq, *nwq;
mutex_lock(&sbi->wq_mutex);
if (sbi->flags & AUTOFS_SBI_CATATONIC) {
mutex_unlock(&sbi->wq_mutex);
return;
}
pr_debug("entering catatonic mode\n");
sbi->flags |= AUTOFS_SBI_CATATONIC;
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.name - wq->offset);
wq->name.name = NULL;
wq->wait_ctr--;
wake_up_interruptible(&wq->queue);
wq = nwq;
}
fput(sbi->pipe); /* Close the pipe */
sbi->pipe = NULL;
sbi->pipefd = -1;
mutex_unlock(&sbi->wq_mutex);
}
static int autofs_write(struct autofs_sb_info *sbi,
struct file *file, const void *addr, int bytes)
{
unsigned long sigpipe, flags;
const char *data = (const char *)addr;
ssize_t wr = 0;
sigpipe = sigismember(&current->pending.signal, SIGPIPE);
mutex_lock(&sbi->pipe_mutex);
while (bytes) {
wr = __kernel_write(file, data, bytes, NULL);
if (wr <= 0)
break;
data += wr;
bytes -= wr;
}
mutex_unlock(&sbi->pipe_mutex);
/* 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);
}
/* if 'wr' returned 0 (impossible) we assume -EIO (safe) */
return bytes == 0 ? 0 : wr < 0 ? wr : -EIO;
}
static void autofs_notify_daemon(struct autofs_sb_info *sbi,
struct autofs_wait_queue *wq,
int type)
{
union {
struct autofs_packet_hdr hdr;
union autofs_packet_union v4_pkt;
union autofs_v5_packet_union v5_pkt;
} pkt;
struct file *pipe = NULL;
size_t pktsz;
int ret;
pr_debug("wait id = 0x%08lx, name = %.*s, type=%d\n",
(unsigned long) wq->wait_queue_token,
wq->name.len, wq->name.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.v4_pkt.missing;
pktsz = sizeof(*mp);
mp->wait_queue_token = wq->wait_queue_token;
mp->len = wq->name.len;
memcpy(mp->name, wq->name.name, wq->name.len);
mp->name[wq->name.len] = '\0';
break;
}
case autofs_ptype_expire_multi:
{
struct autofs_packet_expire_multi *ep =
&pkt.v4_pkt.expire_multi;
pktsz = sizeof(*ep);
ep->wait_queue_token = wq->wait_queue_token;
ep->len = wq->name.len;
memcpy(ep->name, wq->name.name, wq->name.len);
ep->name[wq->name.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_pkt.v5_packet;
struct user_namespace *user_ns = sbi->pipe->f_cred->user_ns;
pktsz = sizeof(*packet);
packet->wait_queue_token = wq->wait_queue_token;
packet->len = wq->name.len;
memcpy(packet->name, wq->name.name, wq->name.len);
packet->name[wq->name.len] = '\0';
packet->dev = wq->dev;
packet->ino = wq->ino;
packet->uid = from_kuid_munged(user_ns, wq->uid);
packet->gid = from_kgid_munged(user_ns, wq->gid);
packet->pid = wq->pid;
packet->tgid = wq->tgid;
break;
}
default:
pr_warn("bad type %d!\n", type);
mutex_unlock(&sbi->wq_mutex);
return;
}
pipe = get_file(sbi->pipe);
mutex_unlock(&sbi->wq_mutex);
switch (ret = autofs_write(sbi, pipe, &pkt, pktsz)) {
case 0:
break;
case -ENOMEM:
case -ERESTARTSYS:
/* Just fail this one */
autofs_wait_release(sbi, wq->wait_queue_token, ret);
break;
default:
autofs_catatonic_mode(sbi);
break;
}
fput(pipe);
}
static struct autofs_wait_queue *
autofs_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
{
struct autofs_wait_queue *wq;
for (wq = sbi->queues; wq; wq = wq->next) {
if (wq->name.hash == qstr->hash &&
wq->name.len == qstr->len &&
wq->name.name &&
!memcmp(wq->name.name, qstr->name, qstr->len))
break;
}
return wq;
}
/*
* Check if we have a valid request.
* Returns
* 1 if the request should continue.
* In this case we can return an autofs_wait_queue entry if one is
* found or NULL to idicate a new wait needs to be created.
* 0 or a negative errno if the request shouldn't continue.
*/
static int validate_request(struct autofs_wait_queue **wait,
struct autofs_sb_info *sbi,
const struct qstr *qstr,
const struct path *path, enum autofs_notify notify)
{
struct dentry *dentry = path->dentry;
struct autofs_wait_queue *wq;
struct autofs_info *ino;
if (sbi->flags & AUTOFS_SBI_CATATONIC)
return -ENOENT;
/* Wait in progress, continue; */
wq = autofs_find_wait(sbi, qstr);
if (wq) {
*wait = wq;
return 1;
}
*wait = NULL;
/* If we don't yet have any info this is a new request */
ino = autofs_dentry_ino(dentry);
if (!ino)
return 1;
/*
* If we've been asked to wait on an existing expire (NFY_NONE)
* but there is no wait in the queue ...
*/
if (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))
return -EINTR;
if (sbi->flags & AUTOFS_SBI_CATATONIC)
return -ENOENT;
wq = autofs_find_wait(sbi, qstr);
if (wq) {
*wait = wq;
return 1;
}
}
/*
* 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.
*/
return 0;
}
/*
* If we've been asked to trigger a mount and the request
* completed while we waited on the mutex ...
*/
if (notify == NFY_MOUNT) {
struct dentry *new = NULL;
struct path this;
int valid = 1;
/*
* If the dentry was successfully mounted while we slept
* on the wait queue mutex we can return success. If it
* isn't mounted (doesn't have submounts for the case of
* a multi-mount with no mount at it's base) we can
* continue on and create a new request.
*/
if (!IS_ROOT(dentry)) {
if (d_unhashed(dentry) &&
d_really_is_positive(dentry)) {
struct dentry *parent = dentry->d_parent;
new = d_lookup(parent, &dentry->d_name);
if (new)
dentry = new;
}
}
this.mnt = path->mnt;
this.dentry = dentry;
if (path_has_submounts(&this))
valid = 0;
if (new)
dput(new);
return valid;
}
return 1;
}
int autofs_wait(struct autofs_sb_info *sbi,
const struct path *path, enum autofs_notify notify)
{
struct dentry *dentry = path->dentry;
struct autofs_wait_queue *wq;
struct qstr qstr;
char *name;
int status, ret, type;
unsigned int offset = 0;
pid_t pid;
pid_t tgid;
/* In catatonic mode, we don't wait for nobody */
if (sbi->flags & AUTOFS_SBI_CATATONIC)
return -ENOENT;
/*
* Try translating pids to the namespace of the daemon.
*
* Zero means failure: we are in an unrelated pid namespace.
*/
pid = task_pid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
tgid = task_tgid_nr_ns(current, ns_of_pid(sbi->oz_pgrp));
if (pid == 0 || tgid == 0)
return -ENOENT;
if (d_really_is_negative(dentry)) {
/*
* A wait for a negative dentry is invalid for certain
* cases. A direct or offset mount "always" has its mount
* point directory created and so the request dentry must
* be positive or the map key doesn't exist. The situation
* is very similar for indirect mounts except only dentrys
* in the root of the autofs file system may be negative.
*/
if (autofs_type_trigger(sbi->type))
return -ENOENT;
else if (!IS_ROOT(dentry->d_parent))
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) && autofs_type_trigger(sbi->type)) {
qstr.name = name;
qstr.len = sprintf(name, "%p", dentry);
} else {
char *p = dentry_path_raw(dentry, name, NAME_MAX);
if (IS_ERR(p)) {
kfree(name);
return -ENOENT;
}
qstr.name = ++p; // skip the leading slash
qstr.len = strlen(p);
offset = p - name;
}
qstr.hash = full_name_hash(dentry, name, qstr.len);
if (mutex_lock_interruptible(&sbi->wq_mutex)) {
kfree(name);
return -EINTR;
}
ret = validate_request(&wq, sbi, &qstr, path, notify);
if (ret <= 0) {
if (ret != -EINTR)
mutex_unlock(&sbi->wq_mutex);
kfree(name);
return ret;
}
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 = autofs_next_wait_queue;
if (++autofs_next_wait_queue == 0)
autofs_next_wait_queue = 1;
wq->next = sbi->queues;
sbi->queues = wq;
init_waitqueue_head(&wq->queue);
memcpy(&wq->name, &qstr, sizeof(struct qstr));
wq->offset = offset;
wq->dev = autofs_get_dev(sbi);
wq->ino = autofs_get_ino(sbi);
wq->uid = current_uid();
wq->gid = current_gid();
wq->pid = pid;
wq->tgid = tgid;
wq->status = -EINTR; /* Status return if interrupted */
wq->wait_ctr = 2;
if (sbi->version < 5) {
if (notify == NFY_MOUNT)
type = autofs_ptype_missing;
else
type = autofs_ptype_expire_multi;
} else {
if (notify == NFY_MOUNT)
type = autofs_type_trigger(sbi->type) ?
autofs_ptype_missing_direct :
autofs_ptype_missing_indirect;
else
type = autofs_type_trigger(sbi->type) ?
autofs_ptype_expire_direct :
autofs_ptype_expire_indirect;
}
pr_debug("new wait id = 0x%08lx, name = %.*s, nfy=%d\n",
(unsigned long) wq->wait_queue_token, wq->name.len,
wq->name.name, notify);
/*
* autofs_notify_daemon() may block; it will unlock ->wq_mutex
*/
autofs_notify_daemon(sbi, wq, type);
} else {
wq->wait_ctr++;
pr_debug("existing wait id = 0x%08lx, name = %.*s, nfy=%d\n",
(unsigned long) wq->wait_queue_token, wq->name.len,
wq->name.name, notify);
mutex_unlock(&sbi->wq_mutex);
kfree(name);
}
/*
* wq->name.name is NULL iff the lock is already released
* or the mount has been made catatonic.
*/
wait_event_killable(wq->queue, wq->name.name == NULL);
status = wq->status;
/*
* For direct and offset mounts we need to track the requester's
* uid and gid in the dentry info struct. This is so it can be
* supplied, on request, by the misc device ioctl interface.
* This is needed during daemon resatart when reconnecting
* to existing, active, autofs mounts. The uid and gid (and
* related string values) may be used for macro substitution
* in autofs mount maps.
*/
if (!status) {
struct autofs_info *ino;
struct dentry *de = NULL;
/* direct mount or browsable map */
ino = autofs_dentry_ino(dentry);
if (!ino) {
/* If not lookup actual dentry used */
de = d_lookup(dentry->d_parent, &dentry->d_name);
if (de)
ino = autofs_dentry_ino(de);
}
/* Set mount requester */
if (ino) {
spin_lock(&sbi->fs_lock);
ino->uid = wq->uid;
ino->gid = wq->gid;
spin_unlock(&sbi->fs_lock);
}
if (de)
dput(de);
}
/* Are we the last process to need status? */
mutex_lock(&sbi->wq_mutex);
if (!--wq->wait_ctr)
kfree(wq);
mutex_unlock(&sbi->wq_mutex);
return status;
}
int autofs_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) != NULL; 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 */
kfree(wq->name.name - wq->offset);
wq->name.name = NULL; /* Do not wait on this queue */
wq->status = status;
wake_up(&wq->queue);
if (!--wq->wait_ctr)
kfree(wq);
mutex_unlock(&sbi->wq_mutex);
return 0;
}