// SPDX-License-Identifier: GPL-2.0-or-later
/* Daemon interface
 *
 * Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/completion.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/namei.h>
#include <linux/poll.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/statfs.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/fs_struct.h>
#include "internal.h"

static int cachefiles_daemon_open(struct inode *, struct file *);
static int cachefiles_daemon_release(struct inode *, struct file *);
static ssize_t cachefiles_daemon_read(struct file *, char __user *, size_t,
                                      loff_t *);
static ssize_t cachefiles_daemon_write(struct file *, const char __user *,
                                       size_t, loff_t *);
static __poll_t cachefiles_daemon_poll(struct file *,
                                           struct poll_table_struct *);
static int cachefiles_daemon_frun(struct cachefiles_cache *, char *);
static int cachefiles_daemon_fcull(struct cachefiles_cache *, char *);
static int cachefiles_daemon_fstop(struct cachefiles_cache *, char *);
static int cachefiles_daemon_brun(struct cachefiles_cache *, char *);
static int cachefiles_daemon_bcull(struct cachefiles_cache *, char *);
static int cachefiles_daemon_bstop(struct cachefiles_cache *, char *);
static int cachefiles_daemon_cull(struct cachefiles_cache *, char *);
static int cachefiles_daemon_debug(struct cachefiles_cache *, char *);
static int cachefiles_daemon_dir(struct cachefiles_cache *, char *);
static int cachefiles_daemon_inuse(struct cachefiles_cache *, char *);
static int cachefiles_daemon_secctx(struct cachefiles_cache *, char *);
static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
static int cachefiles_daemon_bind(struct cachefiles_cache *, char *);
static void cachefiles_daemon_unbind(struct cachefiles_cache *);

static unsigned long cachefiles_open;

const struct file_operations cachefiles_daemon_fops = {
        .owner          = THIS_MODULE,
        .open           = cachefiles_daemon_open,
        .release        = cachefiles_daemon_release,
        .read           = cachefiles_daemon_read,
        .write          = cachefiles_daemon_write,
        .poll           = cachefiles_daemon_poll,
        .llseek         = noop_llseek,
};

struct cachefiles_daemon_cmd {
        char name[8];
        int (*handler)(struct cachefiles_cache *cache, char *args);
};

static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
        { "bind",       cachefiles_daemon_bind          },
        { "brun",       cachefiles_daemon_brun          },
        { "bcull",      cachefiles_daemon_bcull         },
        { "bstop",      cachefiles_daemon_bstop         },
        { "cull",       cachefiles_daemon_cull          },
        { "debug",      cachefiles_daemon_debug         },
        { "dir",        cachefiles_daemon_dir           },
        { "frun",       cachefiles_daemon_frun          },
        { "fcull",      cachefiles_daemon_fcull         },
        { "fstop",      cachefiles_daemon_fstop         },
        { "inuse",      cachefiles_daemon_inuse         },
        { "secctx",     cachefiles_daemon_secctx        },
        { "tag",        cachefiles_daemon_tag           },
#ifdef CONFIG_CACHEFILES_ONDEMAND
        { "copen",      cachefiles_ondemand_copen       },
        { "restore",    cachefiles_ondemand_restore     },
#endif
        { "",           NULL                            }
};


/*
 * Prepare a cache for caching.
 */
static int cachefiles_daemon_open(struct inode *inode, struct file *file)
{
        struct cachefiles_cache *cache;

        _enter("");

        /* only the superuser may do this */
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;

        /* the cachefiles device may only be open once at a time */
        if (xchg(&cachefiles_open, 1) == 1)
                return -EBUSY;

        /* allocate a cache record */
        cache = kzalloc_obj(struct cachefiles_cache);
        if (!cache) {
                cachefiles_open = 0;
                return -ENOMEM;
        }

        mutex_init(&cache->daemon_mutex);
        init_waitqueue_head(&cache->daemon_pollwq);
        INIT_LIST_HEAD(&cache->volumes);
        INIT_LIST_HEAD(&cache->object_list);
        spin_lock_init(&cache->object_list_lock);
        refcount_set(&cache->unbind_pincount, 1);
        xa_init_flags(&cache->reqs, XA_FLAGS_ALLOC);
        xa_init_flags(&cache->ondemand_ids, XA_FLAGS_ALLOC1);

        /* set default caching limits
         * - limit at 1% free space and/or free files
         * - cull below 5% free space and/or free files
         * - cease culling above 7% free space and/or free files
         */
        cache->frun_percent = 7;
        cache->fcull_percent = 5;
        cache->fstop_percent = 1;
        cache->brun_percent = 7;
        cache->bcull_percent = 5;
        cache->bstop_percent = 1;

        file->private_data = cache;
        cache->cachefilesd = file;
        return 0;
}

void cachefiles_flush_reqs(struct cachefiles_cache *cache)
{
        struct xarray *xa = &cache->reqs;
        struct cachefiles_req *req;
        unsigned long index;

        /*
         * Make sure the following two operations won't be reordered.
         *   1) set CACHEFILES_DEAD bit
         *   2) flush requests in the xarray
         * Otherwise the request may be enqueued after xarray has been
         * flushed, leaving the orphan request never being completed.
         *
         * CPU 1                        CPU 2
         * =====                        =====
         * flush requests in the xarray
         *                              test CACHEFILES_DEAD bit
         *                              enqueue the request
         * set CACHEFILES_DEAD bit
         */
        smp_mb();

        xa_lock(xa);
        xa_for_each(xa, index, req) {
                req->error = -EIO;
                complete(&req->done);
                __xa_erase(xa, index);
        }
        xa_unlock(xa);

        xa_destroy(&cache->reqs);
        xa_destroy(&cache->ondemand_ids);
}

void cachefiles_put_unbind_pincount(struct cachefiles_cache *cache)
{
        if (refcount_dec_and_test(&cache->unbind_pincount)) {
                cachefiles_daemon_unbind(cache);
                cachefiles_open = 0;
                kfree(cache);
        }
}

void cachefiles_get_unbind_pincount(struct cachefiles_cache *cache)
{
        refcount_inc(&cache->unbind_pincount);
}

/*
 * Release a cache.
 */
static int cachefiles_daemon_release(struct inode *inode, struct file *file)
{
        struct cachefiles_cache *cache = file->private_data;

        _enter("");

        ASSERT(cache);

        set_bit(CACHEFILES_DEAD, &cache->flags);

        if (cachefiles_in_ondemand_mode(cache))
                cachefiles_flush_reqs(cache);

        /* clean up the control file interface */
        cache->cachefilesd = NULL;
        file->private_data = NULL;

        cachefiles_put_unbind_pincount(cache);

        _leave("");
        return 0;
}

static ssize_t cachefiles_do_daemon_read(struct cachefiles_cache *cache,
                                         char __user *_buffer, size_t buflen)
{
        unsigned long long b_released;
        unsigned f_released;
        char buffer[256];
        int n;

        /* check how much space the cache has */
        cachefiles_has_space(cache, 0, 0, cachefiles_has_space_check);

        /* summarise */
        f_released = atomic_xchg(&cache->f_released, 0);
        b_released = atomic_long_xchg(&cache->b_released, 0);
        clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);

        n = snprintf(buffer, sizeof(buffer),
                     "cull=%c"
                     " frun=%llx"
                     " fcull=%llx"
                     " fstop=%llx"
                     " brun=%llx"
                     " bcull=%llx"
                     " bstop=%llx"
                     " freleased=%x"
                     " breleased=%llx",
                     test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
                     (unsigned long long) cache->frun,
                     (unsigned long long) cache->fcull,
                     (unsigned long long) cache->fstop,
                     (unsigned long long) cache->brun,
                     (unsigned long long) cache->bcull,
                     (unsigned long long) cache->bstop,
                     f_released,
                     b_released);

        if (n > buflen)
                return -EMSGSIZE;

        if (copy_to_user(_buffer, buffer, n) != 0)
                return -EFAULT;

        return n;
}

/*
 * Read the cache state.
 */
static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
                                      size_t buflen, loff_t *pos)
{
        struct cachefiles_cache *cache = file->private_data;

        //_enter(",,%zu,", buflen);

        if (!test_bit(CACHEFILES_READY, &cache->flags))
                return 0;

        if (cachefiles_in_ondemand_mode(cache))
                return cachefiles_ondemand_daemon_read(cache, _buffer, buflen);
        else
                return cachefiles_do_daemon_read(cache, _buffer, buflen);
}

/*
 * Take a command from cachefilesd, parse it and act on it.
 */
static ssize_t cachefiles_daemon_write(struct file *file,
                                       const char __user *_data,
                                       size_t datalen,
                                       loff_t *pos)
{
        const struct cachefiles_daemon_cmd *cmd;
        struct cachefiles_cache *cache = file->private_data;
        ssize_t ret;
        char *data, *args, *cp;

        //_enter(",,%zu,", datalen);

        ASSERT(cache);

        if (test_bit(CACHEFILES_DEAD, &cache->flags))
                return -EIO;

        if (datalen > PAGE_SIZE - 1)
                return -EOPNOTSUPP;

        /* drag the command string into the kernel so we can parse it */
        data = memdup_user_nul(_data, datalen);
        if (IS_ERR(data))
                return PTR_ERR(data);

        ret = -EINVAL;
        if (memchr(data, '\0', datalen))
                goto error;

        /* strip any newline */
        cp = memchr(data, '\n', datalen);
        if (cp) {
                if (cp == data)
                        goto error;

                *cp = '\0';
        }

        /* parse the command */
        ret = -EOPNOTSUPP;

        for (args = data; *args; args++)
                if (isspace(*args))
                        break;
        if (*args) {
                if (args == data)
                        goto error;
                *args = '\0';
                args = skip_spaces(++args);
        }

        /* run the appropriate command handler */
        for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
                if (strcmp(cmd->name, data) == 0)
                        goto found_command;

error:
        kfree(data);
        //_leave(" = %zd", ret);
        return ret;

found_command:
        mutex_lock(&cache->daemon_mutex);

        ret = -EIO;
        if (!test_bit(CACHEFILES_DEAD, &cache->flags))
                ret = cmd->handler(cache, args);

        mutex_unlock(&cache->daemon_mutex);

        if (ret == 0)
                ret = datalen;
        goto error;
}

/*
 * Poll for culling state
 * - use EPOLLOUT to indicate culling state
 */
static __poll_t cachefiles_daemon_poll(struct file *file,
                                           struct poll_table_struct *poll)
{
        struct cachefiles_cache *cache = file->private_data;
        XA_STATE(xas, &cache->reqs, 0);
        struct cachefiles_req *req;
        __poll_t mask;

        poll_wait(file, &cache->daemon_pollwq, poll);
        mask = 0;

        if (cachefiles_in_ondemand_mode(cache)) {
                if (!xa_empty(&cache->reqs)) {
                        xas_lock(&xas);
                        xas_for_each_marked(&xas, req, ULONG_MAX, CACHEFILES_REQ_NEW) {
                                if (!cachefiles_ondemand_is_reopening_read(req)) {
                                        mask |= EPOLLIN;
                                        break;
                                }
                        }
                        xas_unlock(&xas);
                }
        } else {
                if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
                        mask |= EPOLLIN;
        }

        if (test_bit(CACHEFILES_CULLING, &cache->flags))
                mask |= EPOLLOUT;

        return mask;
}

/*
 * Give a range error for cache space constraints
 * - can be tail-called
 */
static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
                                         char *args)
{
        pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");

        return -EINVAL;
}

/*
 * Set the percentage of files at which to stop culling
 * - command: "frun <N>%"
 */
static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
{
        unsigned long frun;

        _enter(",%s", args);

        if (!*args)
                return -EINVAL;

        frun = simple_strtoul(args, &args, 10);
        if (args[0] != '%' || args[1] != '\0')
                return -EINVAL;

        if (frun <= cache->fcull_percent || frun >= 100)
                return cachefiles_daemon_range_error(cache, args);

        cache->frun_percent = frun;
        return 0;
}

/*
 * Set the percentage of files at which to start culling
 * - command: "fcull <N>%"
 */
static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
{
        unsigned long fcull;

        _enter(",%s", args);

        if (!*args)
                return -EINVAL;

        fcull = simple_strtoul(args, &args, 10);
        if (args[0] != '%' || args[1] != '\0')
                return -EINVAL;

        if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
                return cachefiles_daemon_range_error(cache, args);

        cache->fcull_percent = fcull;
        return 0;
}

/*
 * Set the percentage of files at which to stop allocating
 * - command: "fstop <N>%"
 */
static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
{
        unsigned long fstop;

        _enter(",%s", args);

        if (!*args)
                return -EINVAL;

        fstop = simple_strtoul(args, &args, 10);
        if (args[0] != '%' || args[1] != '\0')
                return -EINVAL;

        if (fstop >= cache->fcull_percent)
                return cachefiles_daemon_range_error(cache, args);

        cache->fstop_percent = fstop;
        return 0;
}

/*
 * Set the percentage of blocks at which to stop culling
 * - command: "brun <N>%"
 */
static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
{
        unsigned long brun;

        _enter(",%s", args);

        if (!*args)
                return -EINVAL;

        brun = simple_strtoul(args, &args, 10);
        if (args[0] != '%' || args[1] != '\0')
                return -EINVAL;

        if (brun <= cache->bcull_percent || brun >= 100)
                return cachefiles_daemon_range_error(cache, args);

        cache->brun_percent = brun;
        return 0;
}

/*
 * Set the percentage of blocks at which to start culling
 * - command: "bcull <N>%"
 */
static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
{
        unsigned long bcull;

        _enter(",%s", args);

        if (!*args)
                return -EINVAL;

        bcull = simple_strtoul(args, &args, 10);
        if (args[0] != '%' || args[1] != '\0')
                return -EINVAL;

        if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
                return cachefiles_daemon_range_error(cache, args);

        cache->bcull_percent = bcull;
        return 0;
}

/*
 * Set the percentage of blocks at which to stop allocating
 * - command: "bstop <N>%"
 */
static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
{
        unsigned long bstop;

        _enter(",%s", args);

        if (!*args)
                return -EINVAL;

        bstop = simple_strtoul(args, &args, 10);
        if (args[0] != '%' || args[1] != '\0')
                return -EINVAL;

        if (bstop >= cache->bcull_percent)
                return cachefiles_daemon_range_error(cache, args);

        cache->bstop_percent = bstop;
        return 0;
}

/*
 * Set the cache directory
 * - command: "dir <name>"
 */
static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
{
        char *dir;

        _enter(",%s", args);

        if (!*args) {
                pr_err("Empty directory specified\n");
                return -EINVAL;
        }

        if (cache->rootdirname) {
                pr_err("Second cache directory specified\n");
                return -EEXIST;
        }

        dir = kstrdup(args, GFP_KERNEL);
        if (!dir)
                return -ENOMEM;

        cache->rootdirname = dir;
        return 0;
}

/*
 * Set the cache security context
 * - command: "secctx <ctx>"
 */
static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
{
        int err;

        _enter(",%s", args);

        if (!*args) {
                pr_err("Empty security context specified\n");
                return -EINVAL;
        }

        if (cache->have_secid) {
                pr_err("Second security context specified\n");
                return -EINVAL;
        }

        err = security_secctx_to_secid(args, strlen(args), &cache->secid);
        if (err)
                return err;

        cache->have_secid = true;
        return 0;
}

/*
 * Set the cache tag
 * - command: "tag <name>"
 */
static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
{
        char *tag;

        _enter(",%s", args);

        if (!*args) {
                pr_err("Empty tag specified\n");
                return -EINVAL;
        }

        if (cache->tag)
                return -EEXIST;

        tag = kstrdup(args, GFP_KERNEL);
        if (!tag)
                return -ENOMEM;

        cache->tag = tag;
        return 0;
}

/*
 * Request a node in the cache be culled from the current working directory
 * - command: "cull <name>"
 */
static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
{
        struct path path;
        const struct cred *saved_cred;
        int ret;

        _enter(",%s", args);

        if (strchr(args, '/'))
                goto inval;

        if (!test_bit(CACHEFILES_READY, &cache->flags)) {
                pr_err("cull applied to unready cache\n");
                return -EIO;
        }

        if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
                pr_err("cull applied to dead cache\n");
                return -EIO;
        }

        get_fs_pwd(current->fs, &path);

        if (!d_can_lookup(path.dentry))
                goto notdir;

        cachefiles_begin_secure(cache, &saved_cred);
        ret = cachefiles_cull(cache, path.dentry, args);
        cachefiles_end_secure(cache, saved_cred);

        path_put(&path);
        _leave(" = %d", ret);
        return ret;

notdir:
        path_put(&path);
        pr_err("cull command requires dirfd to be a directory\n");
        return -ENOTDIR;

inval:
        pr_err("cull command requires dirfd and filename\n");
        return -EINVAL;
}

/*
 * Set debugging mode
 * - command: "debug <mask>"
 */
static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
{
        unsigned long mask;

        _enter(",%s", args);

        mask = simple_strtoul(args, &args, 0);
        if (args[0] != '\0')
                goto inval;

        cachefiles_debug = mask;
        _leave(" = 0");
        return 0;

inval:
        pr_err("debug command requires mask\n");
        return -EINVAL;
}

/*
 * Find out whether an object in the current working directory is in use or not
 * - command: "inuse <name>"
 */
static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
{
        struct path path;
        const struct cred *saved_cred;
        int ret;

        //_enter(",%s", args);

        if (strchr(args, '/'))
                goto inval;

        if (!test_bit(CACHEFILES_READY, &cache->flags)) {
                pr_err("inuse applied to unready cache\n");
                return -EIO;
        }

        if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
                pr_err("inuse applied to dead cache\n");
                return -EIO;
        }

        get_fs_pwd(current->fs, &path);

        if (!d_can_lookup(path.dentry))
                goto notdir;

        cachefiles_begin_secure(cache, &saved_cred);
        ret = cachefiles_check_in_use(cache, path.dentry, args);
        cachefiles_end_secure(cache, saved_cred);

        path_put(&path);
        //_leave(" = %d", ret);
        return ret;

notdir:
        path_put(&path);
        pr_err("inuse command requires dirfd to be a directory\n");
        return -ENOTDIR;

inval:
        pr_err("inuse command requires dirfd and filename\n");
        return -EINVAL;
}

/*
 * Bind a directory as a cache
 */
static int cachefiles_daemon_bind(struct cachefiles_cache *cache, char *args)
{
        _enter("{%u,%u,%u,%u,%u,%u},%s",
               cache->frun_percent,
               cache->fcull_percent,
               cache->fstop_percent,
               cache->brun_percent,
               cache->bcull_percent,
               cache->bstop_percent,
               args);

        if (cache->fstop_percent >= cache->fcull_percent ||
            cache->fcull_percent >= cache->frun_percent ||
            cache->frun_percent  >= 100)
                return -ERANGE;

        if (cache->bstop_percent >= cache->bcull_percent ||
            cache->bcull_percent >= cache->brun_percent ||
            cache->brun_percent  >= 100)
                return -ERANGE;

        if (!cache->rootdirname) {
                pr_err("No cache directory specified\n");
                return -EINVAL;
        }

        /* Don't permit already bound caches to be re-bound */
        if (test_bit(CACHEFILES_READY, &cache->flags)) {
                pr_err("Cache already bound\n");
                return -EBUSY;
        }

        if (IS_ENABLED(CONFIG_CACHEFILES_ONDEMAND)) {
                if (!strcmp(args, "ondemand")) {
                        set_bit(CACHEFILES_ONDEMAND_MODE, &cache->flags);
                } else if (*args) {
                        pr_err("Invalid argument to the 'bind' command\n");
                        return -EINVAL;
                }
        } else if (*args) {
                pr_err("'bind' command doesn't take an argument\n");
                return -EINVAL;
        }

        /* Make sure we have copies of the tag string */
        if (!cache->tag) {
                /*
                 * The tag string is released by the fops->release()
                 * function, so we don't release it on error here
                 */
                cache->tag = kstrdup("CacheFiles", GFP_KERNEL);
                if (!cache->tag)
                        return -ENOMEM;
        }

        return cachefiles_add_cache(cache);
}

/*
 * Unbind a cache.
 */
static void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
{
        _enter("");

        if (test_bit(CACHEFILES_READY, &cache->flags))
                cachefiles_withdraw_cache(cache);

        cachefiles_put_directory(cache->graveyard);
        cachefiles_put_directory(cache->store);
        mntput(cache->mnt);
        put_cred(cache->cache_cred);

        kfree(cache->rootdirname);
        kfree(cache->tag);

        _leave("");
}