// 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, qstr.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;
}