OSCL-LXR linux-6.0.1/​fs/​notify/​fanotify/​fanotify_user.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/fanotify.h>
 #include <linux/fcntl.h>
 #include <linux/fdtable.h>
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/anon_inodes.h>
 #include <linux/fsnotify_backend.h>
 #include <linux/init.h>
 #include <linux/mount.h>
 #include <linux/namei.h>
 #include <linux/poll.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/uaccess.h>
 #include <linux/compat.h>
 #include <linux/sched/signal.h>
 #include <linux/memcontrol.h>
 #include <linux/statfs.h>
 #include <linux/exportfs.h>
 
 #include <asm/ioctls.h>
 
 #include "../../mount.h"
 #include "../fdinfo.h"
 #include "fanotify.h"
 
 #define FANOTIFY_DEFAULT_MAX_EVENTS 16384
 #define FANOTIFY_OLD_DEFAULT_MAX_MARKS  8192
 #define FANOTIFY_DEFAULT_MAX_GROUPS 128
 #define FANOTIFY_DEFAULT_FEE_POOL_SIZE  32
 
 /*
  * Legacy fanotify marks limits (8192) is per group and we introduced a tunable
  * limit of marks per user, similar to inotify.  Effectively, the legacy limit
  * of fanotify marks per user is <max marks per group> * <max groups per user>.
  * This default limit (1M) also happens to match the increased limit of inotify
  * max_user_watches since v5.10.
  */
 #define FANOTIFY_DEFAULT_MAX_USER_MARKS \
     (FANOTIFY_OLD_DEFAULT_MAX_MARKS * FANOTIFY_DEFAULT_MAX_GROUPS)
 
 /*
  * Most of the memory cost of adding an inode mark is pinning the marked inode.
  * The size of the filesystem inode struct is not uniform across filesystems,
  * so double the size of a VFS inode is used as a conservative approximation.
  */
 #define INODE_MARK_COST (2 * sizeof(struct inode))
 
 /* configurable via /proc/sys/fs/fanotify/ */
 static int fanotify_max_queued_events __read_mostly;
 
 #ifdef CONFIG_SYSCTL
 
 #include <linux/sysctl.h>
 
 static long ft_zero = 0;
 static long ft_int_max = INT_MAX;
 
 static struct ctl_table fanotify_table[] = {
     {
         .procname   = "max_user_groups",
         .data   = &init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS],
         .maxlen     = sizeof(long),
         .mode       = 0644,
         .proc_handler   = proc_doulongvec_minmax,
         .extra1     = &ft_zero,
         .extra2     = &ft_int_max,
     },
     {
         .procname   = "max_user_marks",
         .data   = &init_user_ns.ucount_max[UCOUNT_FANOTIFY_MARKS],
         .maxlen     = sizeof(long),
         .mode       = 0644,
         .proc_handler   = proc_doulongvec_minmax,
         .extra1     = &ft_zero,
         .extra2     = &ft_int_max,
     },
     {
         .procname   = "max_queued_events",
         .data       = &fanotify_max_queued_events,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_dointvec_minmax,
         .extra1     = SYSCTL_ZERO
     },
     { }
 };
 
 static void __init fanotify_sysctls_init(void)
 {
     register_sysctl("fs/fanotify", fanotify_table);
 }
 #else
 #define fanotify_sysctls_init() do { } while (0)
 #endif /* CONFIG_SYSCTL */
 
 /*
  * All flags that may be specified in parameter event_f_flags of fanotify_init.
  *
  * Internal and external open flags are stored together in field f_flags of
  * struct file. Only external open flags shall be allowed in event_f_flags.
  * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
  * excluded.
  */
 #define FANOTIFY_INIT_ALL_EVENT_F_BITS              ( \
         O_ACCMODE   | O_APPEND  | O_NONBLOCK    | \
         __O_SYNC    | O_DSYNC   | O_CLOEXEC     | \
         O_LARGEFILE | O_NOATIME )
 
 extern const struct fsnotify_ops fanotify_fsnotify_ops;
 
 struct kmem_cache *fanotify_mark_cache __read_mostly;
 struct kmem_cache *fanotify_fid_event_cachep __read_mostly;
 struct kmem_cache *fanotify_path_event_cachep __read_mostly;
 struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
 
 #define FANOTIFY_EVENT_ALIGN 4
 #define FANOTIFY_FID_INFO_HDR_LEN \
     (sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle))
 #define FANOTIFY_PIDFD_INFO_HDR_LEN \
     sizeof(struct fanotify_event_info_pidfd)
 #define FANOTIFY_ERROR_INFO_LEN \
     (sizeof(struct fanotify_event_info_error))
 
 static int fanotify_fid_info_len(int fh_len, int name_len)
 {
     int info_len = fh_len;
 
     if (name_len)
         info_len += name_len + 1;
 
     return roundup(FANOTIFY_FID_INFO_HDR_LEN + info_len,
                FANOTIFY_EVENT_ALIGN);
 }
 
 /* FAN_RENAME may have one or two dir+name info records */
 static int fanotify_dir_name_info_len(struct fanotify_event *event)
 {
     struct fanotify_info *info = fanotify_event_info(event);
     int dir_fh_len = fanotify_event_dir_fh_len(event);
     int dir2_fh_len = fanotify_event_dir2_fh_len(event);
     int info_len = 0;
 
     if (dir_fh_len)
         info_len += fanotify_fid_info_len(dir_fh_len,
                           info->name_len);
     if (dir2_fh_len)
         info_len += fanotify_fid_info_len(dir2_fh_len,
                           info->name2_len);
 
     return info_len;
 }
 
 static size_t fanotify_event_len(unsigned int info_mode,
                  struct fanotify_event *event)
 {
     size_t event_len = FAN_EVENT_METADATA_LEN;
     int fh_len;
     int dot_len = 0;
 
     if (!info_mode)
         return event_len;
 
     if (fanotify_is_error_event(event->mask))
         event_len += FANOTIFY_ERROR_INFO_LEN;
 
     if (fanotify_event_has_any_dir_fh(event)) {
         event_len += fanotify_dir_name_info_len(event);
     } else if ((info_mode & FAN_REPORT_NAME) &&
            (event->mask & FAN_ONDIR)) {
         /*
          * With group flag FAN_REPORT_NAME, if name was not recorded in
          * event on a directory, we will report the name ".".
          */
         dot_len = 1;
     }
 
     if (info_mode & FAN_REPORT_PIDFD)
         event_len += FANOTIFY_PIDFD_INFO_HDR_LEN;
 
     if (fanotify_event_has_object_fh(event)) {
         fh_len = fanotify_event_object_fh_len(event);
         event_len += fanotify_fid_info_len(fh_len, dot_len);
     }
 
     return event_len;
 }
 
 /*
  * Remove an hashed event from merge hash table.
  */
 static void fanotify_unhash_event(struct fsnotify_group *group,
                   struct fanotify_event *event)
 {
     assert_spin_locked(&group->notification_lock);
 
     pr_debug("%s: group=%p event=%p bucket=%u\n", __func__,
          group, event, fanotify_event_hash_bucket(group, event));
 
     if (WARN_ON_ONCE(hlist_unhashed(&event->merge_list)))
         return;
 
     hlist_del_init(&event->merge_list);
 }
 
 /*
  * Get an fanotify notification event if one exists and is small
  * enough to fit in "count". Return an error pointer if the count
  * is not large enough. When permission event is dequeued, its state is
  * updated accordingly.
  */
 static struct fanotify_event *get_one_event(struct fsnotify_group *group,
                         size_t count)
 {
     size_t event_size;
     struct fanotify_event *event = NULL;
     struct fsnotify_event *fsn_event;
     unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
 
     pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
 
     spin_lock(&group->notification_lock);
     fsn_event = fsnotify_peek_first_event(group);
     if (!fsn_event)
         goto out;
 
     event = FANOTIFY_E(fsn_event);
     event_size = fanotify_event_len(info_mode, event);
 
     if (event_size > count) {
         event = ERR_PTR(-EINVAL);
         goto out;
     }
 
     /*
      * Held the notification_lock the whole time, so this is the
      * same event we peeked above.
      */
     fsnotify_remove_first_event(group);
     if (fanotify_is_perm_event(event->mask))
         FANOTIFY_PERM(event)->state = FAN_EVENT_REPORTED;
     if (fanotify_is_hashed_event(event->mask))
         fanotify_unhash_event(group, event);
 out:
     spin_unlock(&group->notification_lock);
     return event;
 }
 
 static int create_fd(struct fsnotify_group *group, struct path *path,
              struct file **file)
 {
     int client_fd;
     struct file *new_file;
 
     client_fd = get_unused_fd_flags(group->fanotify_data.f_flags);
     if (client_fd < 0)
         return client_fd;
 
     /*
      * we need a new file handle for the userspace program so it can read even if it was
      * originally opened O_WRONLY.
      */
     new_file = dentry_open(path,
                    group->fanotify_data.f_flags | __FMODE_NONOTIFY,
                    current_cred());
     if (IS_ERR(new_file)) {
         /*
          * we still send an event even if we can't open the file.  this
          * can happen when say tasks are gone and we try to open their
          * /proc files or we try to open a WRONLY file like in sysfs
          * we just send the errno to userspace since there isn't much
          * else we can do.
          */
         put_unused_fd(client_fd);
         client_fd = PTR_ERR(new_file);
     } else {
         *file = new_file;
     }
 
     return client_fd;
 }
 
 /*
  * Finish processing of permission event by setting it to ANSWERED state and
  * drop group->notification_lock.
  */
 static void finish_permission_event(struct fsnotify_group *group,
                     struct fanotify_perm_event *event,
                     unsigned int response)
                     __releases(&group->notification_lock)
 {
     bool destroy = false;
 
     assert_spin_locked(&group->notification_lock);
     event->response = response;
     if (event->state == FAN_EVENT_CANCELED)
         destroy = true;
     else
         event->state = FAN_EVENT_ANSWERED;
     spin_unlock(&group->notification_lock);
     if (destroy)
         fsnotify_destroy_event(group, &event->fae.fse);
 }
 
 static int process_access_response(struct fsnotify_group *group,
                    struct fanotify_response *response_struct)
 {
     struct fanotify_perm_event *event;
     int fd = response_struct->fd;
     int response = response_struct->response;
 
     pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
          fd, response);
     /*
      * make sure the response is valid, if invalid we do nothing and either
      * userspace can send a valid response or we will clean it up after the
      * timeout
      */
     switch (response & ~FAN_AUDIT) {
     case FAN_ALLOW:
     case FAN_DENY:
         break;
     default:
         return -EINVAL;
     }
 
     if (fd < 0)
         return -EINVAL;
 
     if ((response & FAN_AUDIT) && !FAN_GROUP_FLAG(group, FAN_ENABLE_AUDIT))
         return -EINVAL;
 
     spin_lock(&group->notification_lock);
     list_for_each_entry(event, &group->fanotify_data.access_list,
                 fae.fse.list) {
         if (event->fd != fd)
             continue;
 
         list_del_init(&event->fae.fse.list);
         finish_permission_event(group, event, response);
         wake_up(&group->fanotify_data.access_waitq);
         return 0;
     }
     spin_unlock(&group->notification_lock);
 
     return -ENOENT;
 }
 
 static size_t copy_error_info_to_user(struct fanotify_event *event,
                       char __user *buf, int count)
 {
     struct fanotify_event_info_error info = { };
     struct fanotify_error_event *fee = FANOTIFY_EE(event);
 
     info.hdr.info_type = FAN_EVENT_INFO_TYPE_ERROR;
     info.hdr.len = FANOTIFY_ERROR_INFO_LEN;
 
     if (WARN_ON(count < info.hdr.len))
         return -EFAULT;
 
     info.error = fee->error;
     info.error_count = fee->err_count;
 
     if (copy_to_user(buf, &info, sizeof(info)))
         return -EFAULT;
 
     return info.hdr.len;
 }
 
 static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
                  int info_type, const char *name,
                  size_t name_len,
                  char __user *buf, size_t count)
 {
     struct fanotify_event_info_fid info = { };
     struct file_handle handle = { };
     unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *fh_buf;
     size_t fh_len = fh ? fh->len : 0;
     size_t info_len = fanotify_fid_info_len(fh_len, name_len);
     size_t len = info_len;
 
     pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n",
          __func__, fh_len, name_len, info_len, count);
 
     if (WARN_ON_ONCE(len < sizeof(info) || len > count))
         return -EFAULT;
 
     /*
      * Copy event info fid header followed by variable sized file handle
      * and optionally followed by variable sized filename.
      */
     switch (info_type) {
     case FAN_EVENT_INFO_TYPE_FID:
     case FAN_EVENT_INFO_TYPE_DFID:
         if (WARN_ON_ONCE(name_len))
             return -EFAULT;
         break;
     case FAN_EVENT_INFO_TYPE_DFID_NAME:
     case FAN_EVENT_INFO_TYPE_OLD_DFID_NAME:
     case FAN_EVENT_INFO_TYPE_NEW_DFID_NAME:
         if (WARN_ON_ONCE(!name || !name_len))
             return -EFAULT;
         break;
     default:
         return -EFAULT;
     }
 
     info.hdr.info_type = info_type;
     info.hdr.len = len;
     info.fsid = *fsid;
     if (copy_to_user(buf, &info, sizeof(info)))
         return -EFAULT;
 
     buf += sizeof(info);
     len -= sizeof(info);
     if (WARN_ON_ONCE(len < sizeof(handle)))
         return -EFAULT;
 
     handle.handle_type = fh->type;
     handle.handle_bytes = fh_len;
 
     /* Mangle handle_type for bad file_handle */
     if (!fh_len)
         handle.handle_type = FILEID_INVALID;
 
     if (copy_to_user(buf, &handle, sizeof(handle)))
         return -EFAULT;
 
     buf += sizeof(handle);
     len -= sizeof(handle);
     if (WARN_ON_ONCE(len < fh_len))
         return -EFAULT;
 
     /*
      * For an inline fh and inline file name, copy through stack to exclude
      * the copy from usercopy hardening protections.
      */
     fh_buf = fanotify_fh_buf(fh);
     if (fh_len <= FANOTIFY_INLINE_FH_LEN) {
         memcpy(bounce, fh_buf, fh_len);
         fh_buf = bounce;
     }
     if (copy_to_user(buf, fh_buf, fh_len))
         return -EFAULT;
 
     buf += fh_len;
     len -= fh_len;
 
     if (name_len) {
         /* Copy the filename with terminating null */
         name_len++;
         if (WARN_ON_ONCE(len < name_len))
             return -EFAULT;
 
         if (copy_to_user(buf, name, name_len))
             return -EFAULT;
 
         buf += name_len;
         len -= name_len;
     }
 
     /* Pad with 0's */
     WARN_ON_ONCE(len < 0 || len >= FANOTIFY_EVENT_ALIGN);
     if (len > 0 && clear_user(buf, len))
         return -EFAULT;
 
     return info_len;
 }
 
 static int copy_pidfd_info_to_user(int pidfd,
                    char __user *buf,
                    size_t count)
 {
     struct fanotify_event_info_pidfd info = { };
     size_t info_len = FANOTIFY_PIDFD_INFO_HDR_LEN;
 
     if (WARN_ON_ONCE(info_len > count))
         return -EFAULT;
 
     info.hdr.info_type = FAN_EVENT_INFO_TYPE_PIDFD;
     info.hdr.len = info_len;
     info.pidfd = pidfd;
 
     if (copy_to_user(buf, &info, info_len))
         return -EFAULT;
 
     return info_len;
 }
 
 static int copy_info_records_to_user(struct fanotify_event *event,
                      struct fanotify_info *info,
                      unsigned int info_mode, int pidfd,
                      char __user *buf, size_t count)
 {
     int ret, total_bytes = 0, info_type = 0;
     unsigned int fid_mode = info_mode & FANOTIFY_FID_BITS;
     unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
 
     /*
      * Event info records order is as follows:
      * 1. dir fid + name
      * 2. (optional) new dir fid + new name
      * 3. (optional) child fid
      */
     if (fanotify_event_has_dir_fh(event)) {
         info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :
                          FAN_EVENT_INFO_TYPE_DFID;
 
         /* FAN_RENAME uses special info types */
         if (event->mask & FAN_RENAME)
             info_type = FAN_EVENT_INFO_TYPE_OLD_DFID_NAME;
 
         ret = copy_fid_info_to_user(fanotify_event_fsid(event),
                         fanotify_info_dir_fh(info),
                         info_type,
                         fanotify_info_name(info),
                         info->name_len, buf, count);
         if (ret < 0)
             return ret;
 
         buf += ret;
         count -= ret;
         total_bytes += ret;
     }
 
     /* New dir fid+name may be reported in addition to old dir fid+name */
     if (fanotify_event_has_dir2_fh(event)) {
         info_type = FAN_EVENT_INFO_TYPE_NEW_DFID_NAME;
         ret = copy_fid_info_to_user(fanotify_event_fsid(event),
                         fanotify_info_dir2_fh(info),
                         info_type,
                         fanotify_info_name2(info),
                         info->name2_len, buf, count);
         if (ret < 0)
             return ret;
 
         buf += ret;
         count -= ret;
         total_bytes += ret;
     }
 
     if (fanotify_event_has_object_fh(event)) {
         const char *dot = NULL;
         int dot_len = 0;
 
         if (fid_mode == FAN_REPORT_FID || info_type) {
             /*
              * With only group flag FAN_REPORT_FID only type FID is
              * reported. Second info record type is always FID.
              */
             info_type = FAN_EVENT_INFO_TYPE_FID;
         } else if ((fid_mode & FAN_REPORT_NAME) &&
                (event->mask & FAN_ONDIR)) {
             /*
              * With group flag FAN_REPORT_NAME, if name was not
              * recorded in an event on a directory, report the name
              * "." with info type DFID_NAME.
              */
             info_type = FAN_EVENT_INFO_TYPE_DFID_NAME;
             dot = ".";
             dot_len = 1;
         } else if ((event->mask & ALL_FSNOTIFY_DIRENT_EVENTS) ||
                (event->mask & FAN_ONDIR)) {
             /*
              * With group flag FAN_REPORT_DIR_FID, a single info
              * record has type DFID for directory entry modification
              * event and for event on a directory.
              */
             info_type = FAN_EVENT_INFO_TYPE_DFID;
         } else {
             /*
              * With group flags FAN_REPORT_DIR_FID|FAN_REPORT_FID,
              * a single info record has type FID for event on a
              * non-directory, when there is no directory to report.
              * For example, on FAN_DELETE_SELF event.
              */
             info_type = FAN_EVENT_INFO_TYPE_FID;
         }
 
         ret = copy_fid_info_to_user(fanotify_event_fsid(event),
                         fanotify_event_object_fh(event),
                         info_type, dot, dot_len,
                         buf, count);
         if (ret < 0)
             return ret;
 
         buf += ret;
         count -= ret;
         total_bytes += ret;
     }
 
     if (pidfd_mode) {
         ret = copy_pidfd_info_to_user(pidfd, buf, count);
         if (ret < 0)
             return ret;
 
         buf += ret;
         count -= ret;
         total_bytes += ret;
     }
 
     if (fanotify_is_error_event(event->mask)) {
         ret = copy_error_info_to_user(event, buf, count);
         if (ret < 0)
             return ret;
         buf += ret;
         count -= ret;
         total_bytes += ret;
     }
 
     return total_bytes;
 }
 
 static ssize_t copy_event_to_user(struct fsnotify_group *group,
                   struct fanotify_event *event,
                   char __user *buf, size_t count)
 {
     struct fanotify_event_metadata metadata;
     struct path *path = fanotify_event_path(event);
     struct fanotify_info *info = fanotify_event_info(event);
     unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
     unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
     struct file *f = NULL;
     int ret, pidfd = FAN_NOPIDFD, fd = FAN_NOFD;
 
     pr_debug("%s: group=%p event=%p\n", __func__, group, event);
 
     metadata.event_len = fanotify_event_len(info_mode, event);
     metadata.metadata_len = FAN_EVENT_METADATA_LEN;
     metadata.vers = FANOTIFY_METADATA_VERSION;
     metadata.reserved = 0;
     metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS;
     metadata.pid = pid_vnr(event->pid);
     /*
      * For an unprivileged listener, event->pid can be used to identify the
      * events generated by the listener process itself, without disclosing
      * the pids of other processes.
      */
     if (FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
         task_tgid(current) != event->pid)
         metadata.pid = 0;
 
     /*
      * For now, fid mode is required for an unprivileged listener and
      * fid mode does not report fd in events.  Keep this check anyway
      * for safety in case fid mode requirement is relaxed in the future
      * to allow unprivileged listener to get events with no fd and no fid.
      */
     if (!FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV) &&
         path && path->mnt && path->dentry) {
         fd = create_fd(group, path, &f);
         if (fd < 0)
             return fd;
     }
     metadata.fd = fd;
 
     if (pidfd_mode) {
         /*
          * Complain if the FAN_REPORT_PIDFD and FAN_REPORT_TID mutual
          * exclusion is ever lifted. At the time of incoporating pidfd
          * support within fanotify, the pidfd API only supported the
          * creation of pidfds for thread-group leaders.
          */
         WARN_ON_ONCE(FAN_GROUP_FLAG(group, FAN_REPORT_TID));
 
         /*
          * The PIDTYPE_TGID check for an event->pid is performed
          * preemptively in an attempt to catch out cases where the event
          * listener reads events after the event generating process has
          * already terminated. Report FAN_NOPIDFD to the event listener
          * in those cases, with all other pidfd creation errors being
          * reported as FAN_EPIDFD.
          */
         if (metadata.pid == 0 ||
             !pid_has_task(event->pid, PIDTYPE_TGID)) {
             pidfd = FAN_NOPIDFD;
         } else {
             pidfd = pidfd_create(event->pid, 0);
             if (pidfd < 0)
                 pidfd = FAN_EPIDFD;
         }
     }
 
     ret = -EFAULT;
     /*
      * Sanity check copy size in case get_one_event() and
      * event_len sizes ever get out of sync.
      */
     if (WARN_ON_ONCE(metadata.event_len > count))
         goto out_close_fd;
 
     if (copy_to_user(buf, &metadata, FAN_EVENT_METADATA_LEN))
         goto out_close_fd;
 
     buf += FAN_EVENT_METADATA_LEN;
     count -= FAN_EVENT_METADATA_LEN;
 
     if (fanotify_is_perm_event(event->mask))
         FANOTIFY_PERM(event)->fd = fd;
 
     if (info_mode) {
         ret = copy_info_records_to_user(event, info, info_mode, pidfd,
                         buf, count);
         if (ret < 0)
             goto out_close_fd;
     }
 
     if (f)
         fd_install(fd, f);
 
     return metadata.event_len;
 
 out_close_fd:
     if (fd != FAN_NOFD) {
         put_unused_fd(fd);
         fput(f);
     }
 
     if (pidfd >= 0)
         close_fd(pidfd);
 
     return ret;
 }
 
 /* intofiy userspace file descriptor functions */
 static __poll_t fanotify_poll(struct file *file, poll_table *wait)
 {
     struct fsnotify_group *group = file->private_data;
     __poll_t ret = 0;
 
     poll_wait(file, &group->notification_waitq, wait);
     spin_lock(&group->notification_lock);
     if (!fsnotify_notify_queue_is_empty(group))
         ret = EPOLLIN | EPOLLRDNORM;
     spin_unlock(&group->notification_lock);
 
     return ret;
 }
 
 static ssize_t fanotify_read(struct file *file, char __user *buf,
                  size_t count, loff_t *pos)
 {
     struct fsnotify_group *group;
     struct fanotify_event *event;
     char __user *start;
     int ret;
     DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
     start = buf;
     group = file->private_data;
 
     pr_debug("%s: group=%p\n", __func__, group);
 
     add_wait_queue(&group->notification_waitq, &wait);
     while (1) {
         /*
          * User can supply arbitrarily large buffer. Avoid softlockups
          * in case there are lots of available events.
          */
         cond_resched();
         event = get_one_event(group, count);
         if (IS_ERR(event)) {
             ret = PTR_ERR(event);
             break;
         }
 
         if (!event) {
             ret = -EAGAIN;
             if (file->f_flags & O_NONBLOCK)
                 break;
 
             ret = -ERESTARTSYS;
             if (signal_pending(current))
                 break;
 
             if (start != buf)
                 break;
 
             wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
             continue;
         }
 
         ret = copy_event_to_user(group, event, buf, count);
         if (unlikely(ret == -EOPENSTALE)) {
             /*
              * We cannot report events with stale fd so drop it.
              * Setting ret to 0 will continue the event loop and
              * do the right thing if there are no more events to
              * read (i.e. return bytes read, -EAGAIN or wait).
              */
             ret = 0;
         }
 
         /*
          * Permission events get queued to wait for response.  Other
          * events can be destroyed now.
          */
         if (!fanotify_is_perm_event(event->mask)) {
             fsnotify_destroy_event(group, &event->fse);
         } else {
             if (ret <= 0) {
                 spin_lock(&group->notification_lock);
                 finish_permission_event(group,
                     FANOTIFY_PERM(event), FAN_DENY);
                 wake_up(&group->fanotify_data.access_waitq);
             } else {
                 spin_lock(&group->notification_lock);
                 list_add_tail(&event->fse.list,
                     &group->fanotify_data.access_list);
                 spin_unlock(&group->notification_lock);
             }
         }
         if (ret < 0)
             break;
         buf += ret;
         count -= ret;
     }
     remove_wait_queue(&group->notification_waitq, &wait);
 
     if (start != buf && ret != -EFAULT)
         ret = buf - start;
     return ret;
 }
 
 static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
 {
     struct fanotify_response response = { .fd = -1, .response = -1 };
     struct fsnotify_group *group;
     int ret;
 
     if (!IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
         return -EINVAL;
 
     group = file->private_data;
 
     if (count < sizeof(response))
         return -EINVAL;
 
     count = sizeof(response);
 
     pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
 
     if (copy_from_user(&response, buf, count))
         return -EFAULT;
 
     ret = process_access_response(group, &response);
     if (ret < 0)
         count = ret;
 
     return count;
 }
 
 static int fanotify_release(struct inode *ignored, struct file *file)
 {
     struct fsnotify_group *group = file->private_data;
     struct fsnotify_event *fsn_event;
 
     /*
      * Stop new events from arriving in the notification queue. since
      * userspace cannot use fanotify fd anymore, no event can enter or
      * leave access_list by now either.
      */
     fsnotify_group_stop_queueing(group);
 
     /*
      * Process all permission events on access_list and notification queue
      * and simulate reply from userspace.
      */
     spin_lock(&group->notification_lock);
     while (!list_empty(&group->fanotify_data.access_list)) {
         struct fanotify_perm_event *event;
 
         event = list_first_entry(&group->fanotify_data.access_list,
                 struct fanotify_perm_event, fae.fse.list);
         list_del_init(&event->fae.fse.list);
         finish_permission_event(group, event, FAN_ALLOW);
         spin_lock(&group->notification_lock);
     }
 
     /*
      * Destroy all non-permission events. For permission events just
      * dequeue them and set the response. They will be freed once the
      * response is consumed and fanotify_get_response() returns.
      */
     while ((fsn_event = fsnotify_remove_first_event(group))) {
         struct fanotify_event *event = FANOTIFY_E(fsn_event);
 
         if (!(event->mask & FANOTIFY_PERM_EVENTS)) {
             spin_unlock(&group->notification_lock);
             fsnotify_destroy_event(group, fsn_event);
         } else {
             finish_permission_event(group, FANOTIFY_PERM(event),
                         FAN_ALLOW);
         }
         spin_lock(&group->notification_lock);
     }
     spin_unlock(&group->notification_lock);
 
     /* Response for all permission events it set, wakeup waiters */
     wake_up(&group->fanotify_data.access_waitq);
 
     /* matches the fanotify_init->fsnotify_alloc_group */
     fsnotify_destroy_group(group);
 
     return 0;
 }
 
 static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
     struct fsnotify_group *group;
     struct fsnotify_event *fsn_event;
     void __user *p;
     int ret = -ENOTTY;
     size_t send_len = 0;
 
     group = file->private_data;
 
     p = (void __user *) arg;
 
     switch (cmd) {
     case FIONREAD:
         spin_lock(&group->notification_lock);
         list_for_each_entry(fsn_event, &group->notification_list, list)
             send_len += FAN_EVENT_METADATA_LEN;
         spin_unlock(&group->notification_lock);
         ret = put_user(send_len, (int __user *) p);
         break;
     }
 
     return ret;
 }
 
 static const struct file_operations fanotify_fops = {
     .show_fdinfo    = fanotify_show_fdinfo,
     .poll       = fanotify_poll,
     .read       = fanotify_read,
     .write      = fanotify_write,
     .fasync     = NULL,
     .release    = fanotify_release,
     .unlocked_ioctl = fanotify_ioctl,
     .compat_ioctl   = compat_ptr_ioctl,
     .llseek     = noop_llseek,
 };
 
 static int fanotify_find_path(int dfd, const char __user *filename,
                   struct path *path, unsigned int flags, __u64 mask,
                   unsigned int obj_type)
 {
     int ret;
 
     pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
          dfd, filename, flags);
 
     if (filename == NULL) {
         struct fd f = fdget(dfd);
 
         ret = -EBADF;
         if (!f.file)
             goto out;
 
         ret = -ENOTDIR;
         if ((flags & FAN_MARK_ONLYDIR) &&
             !(S_ISDIR(file_inode(f.file)->i_mode))) {
             fdput(f);
             goto out;
         }
 
         *path = f.file->f_path;
         path_get(path);
         fdput(f);
     } else {
         unsigned int lookup_flags = 0;
 
         if (!(flags & FAN_MARK_DONT_FOLLOW))
             lookup_flags |= LOOKUP_FOLLOW;
         if (flags & FAN_MARK_ONLYDIR)
             lookup_flags |= LOOKUP_DIRECTORY;
 
         ret = user_path_at(dfd, filename, lookup_flags, path);
         if (ret)
             goto out;
     }
 
     /* you can only watch an inode if you have read permissions on it */
     ret = path_permission(path, MAY_READ);
     if (ret) {
         path_put(path);
         goto out;
     }
 
     ret = security_path_notify(path, mask, obj_type);
     if (ret)
         path_put(path);
 
 out:
     return ret;
 }
 
 static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
                         __u32 mask, unsigned int flags,
                         __u32 umask, int *destroy)
 {
     __u32 oldmask, newmask;
 
     /* umask bits cannot be removed by user */
     mask &= ~umask;
     spin_lock(&fsn_mark->lock);
     oldmask = fsnotify_calc_mask(fsn_mark);
     if (!(flags & FANOTIFY_MARK_IGNORE_BITS)) {
         fsn_mark->mask &= ~mask;
     } else {
         fsn_mark->ignore_mask &= ~mask;
     }
     newmask = fsnotify_calc_mask(fsn_mark);
     /*
      * We need to keep the mark around even if remaining mask cannot
      * result in any events (e.g. mask == FAN_ONDIR) to support incremenal
      * changes to the mask.
      * Destroy mark when only umask bits remain.
      */
     *destroy = !((fsn_mark->mask | fsn_mark->ignore_mask) & ~umask);
     spin_unlock(&fsn_mark->lock);
 
     return oldmask & ~newmask;
 }
 
 static int fanotify_remove_mark(struct fsnotify_group *group,
                 fsnotify_connp_t *connp, __u32 mask,
                 unsigned int flags, __u32 umask)
 {
     struct fsnotify_mark *fsn_mark = NULL;
     __u32 removed;
     int destroy_mark;
 
     fsnotify_group_lock(group);
     fsn_mark = fsnotify_find_mark(connp, group);
     if (!fsn_mark) {
         fsnotify_group_unlock(group);
         return -ENOENT;
     }
 
     removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags,
                          umask, &destroy_mark);
     if (removed & fsnotify_conn_mask(fsn_mark->connector))
         fsnotify_recalc_mask(fsn_mark->connector);
     if (destroy_mark)
         fsnotify_detach_mark(fsn_mark);
     fsnotify_group_unlock(group);
     if (destroy_mark)
         fsnotify_free_mark(fsn_mark);
 
     /* matches the fsnotify_find_mark() */
     fsnotify_put_mark(fsn_mark);
     return 0;
 }
 
 static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
                      struct vfsmount *mnt, __u32 mask,
                      unsigned int flags, __u32 umask)
 {
     return fanotify_remove_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
                     mask, flags, umask);
 }
 
 static int fanotify_remove_sb_mark(struct fsnotify_group *group,
                    struct super_block *sb, __u32 mask,
                    unsigned int flags, __u32 umask)
 {
     return fanotify_remove_mark(group, &sb->s_fsnotify_marks, mask,
                     flags, umask);
 }
 
 static int fanotify_remove_inode_mark(struct fsnotify_group *group,
                       struct inode *inode, __u32 mask,
                       unsigned int flags, __u32 umask)
 {
     return fanotify_remove_mark(group, &inode->i_fsnotify_marks, mask,
                     flags, umask);
 }
 
 static bool fanotify_mark_update_flags(struct fsnotify_mark *fsn_mark,
                        unsigned int fan_flags)
 {
     bool want_iref = !(fan_flags & FAN_MARK_EVICTABLE);
     unsigned int ignore = fan_flags & FANOTIFY_MARK_IGNORE_BITS;
     bool recalc = false;
 
     /*
      * When using FAN_MARK_IGNORE for the first time, mark starts using
      * independent event flags in ignore mask.  After that, trying to
      * update the ignore mask with the old FAN_MARK_IGNORED_MASK API
      * will result in EEXIST error.
      */
     if (ignore == FAN_MARK_IGNORE)
         fsn_mark->flags |= FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS;
 
     /*
      * Setting FAN_MARK_IGNORED_SURV_MODIFY for the first time may lead to
      * the removal of the FS_MODIFY bit in calculated mask if it was set
      * because of an ignore mask that is now going to survive FS_MODIFY.
      */
     if (ignore && (fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
         !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)) {
         fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
         if (!(fsn_mark->mask & FS_MODIFY))
             recalc = true;
     }
 
     if (fsn_mark->connector->type != FSNOTIFY_OBJ_TYPE_INODE ||
         want_iref == !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
         return recalc;
 
     /*
      * NO_IREF may be removed from a mark, but not added.
      * When removed, fsnotify_recalc_mask() will take the inode ref.
      */
     WARN_ON_ONCE(!want_iref);
     fsn_mark->flags &= ~FSNOTIFY_MARK_FLAG_NO_IREF;
 
     return true;
 }
 
 static bool fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
                       __u32 mask, unsigned int fan_flags)
 {
     bool recalc;
 
     spin_lock(&fsn_mark->lock);
     if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS))
         fsn_mark->mask |= mask;
     else
         fsn_mark->ignore_mask |= mask;
 
     recalc = fsnotify_calc_mask(fsn_mark) &
         ~fsnotify_conn_mask(fsn_mark->connector);
 
     recalc |= fanotify_mark_update_flags(fsn_mark, fan_flags);
     spin_unlock(&fsn_mark->lock);
 
     return recalc;
 }
 
 static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group,
                            fsnotify_connp_t *connp,
                            unsigned int obj_type,
                            unsigned int fan_flags,
                            __kernel_fsid_t *fsid)
 {
     struct ucounts *ucounts = group->fanotify_data.ucounts;
     struct fsnotify_mark *mark;
     int ret;
 
     /*
      * Enforce per user marks limits per user in all containing user ns.
      * A group with FAN_UNLIMITED_MARKS does not contribute to mark count
      * in the limited groups account.
      */
     if (!FAN_GROUP_FLAG(group, FAN_UNLIMITED_MARKS) &&
         !inc_ucount(ucounts->ns, ucounts->uid, UCOUNT_FANOTIFY_MARKS))
         return ERR_PTR(-ENOSPC);
 
     mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
     if (!mark) {
         ret = -ENOMEM;
         goto out_dec_ucounts;
     }
 
     fsnotify_init_mark(mark, group);
     if (fan_flags & FAN_MARK_EVICTABLE)
         mark->flags |= FSNOTIFY_MARK_FLAG_NO_IREF;
 
     ret = fsnotify_add_mark_locked(mark, connp, obj_type, 0, fsid);
     if (ret) {
         fsnotify_put_mark(mark);
         goto out_dec_ucounts;
     }
 
     return mark;
 
 out_dec_ucounts:
     if (!FAN_GROUP_FLAG(group, FAN_UNLIMITED_MARKS))
         dec_ucount(ucounts, UCOUNT_FANOTIFY_MARKS);
     return ERR_PTR(ret);
 }
 
 static int fanotify_group_init_error_pool(struct fsnotify_group *group)
 {
     if (mempool_initialized(&group->fanotify_data.error_events_pool))
         return 0;
 
     return mempool_init_kmalloc_pool(&group->fanotify_data.error_events_pool,
                      FANOTIFY_DEFAULT_FEE_POOL_SIZE,
                      sizeof(struct fanotify_error_event));
 }
 
 static int fanotify_may_update_existing_mark(struct fsnotify_mark *fsn_mark,
                           unsigned int fan_flags)
 {
     /*
      * Non evictable mark cannot be downgraded to evictable mark.
      */
     if (fan_flags & FAN_MARK_EVICTABLE &&
         !(fsn_mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
         return -EEXIST;
 
     /*
      * New ignore mask semantics cannot be downgraded to old semantics.
      */
     if (fan_flags & FAN_MARK_IGNORED_MASK &&
         fsn_mark->flags & FSNOTIFY_MARK_FLAG_HAS_IGNORE_FLAGS)
         return -EEXIST;
 
     /*
      * An ignore mask that survives modify could never be downgraded to not
      * survive modify.  With new FAN_MARK_IGNORE semantics we make that rule
      * explicit and return an error when trying to update the ignore mask
      * without the original FAN_MARK_IGNORED_SURV_MODIFY value.
      */
     if (fan_flags & FAN_MARK_IGNORE &&
         !(fan_flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
         fsn_mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY)
         return -EEXIST;
 
     return 0;
 }
 
 static int fanotify_add_mark(struct fsnotify_group *group,
                  fsnotify_connp_t *connp, unsigned int obj_type,
                  __u32 mask, unsigned int fan_flags,
                  __kernel_fsid_t *fsid)
 {
     struct fsnotify_mark *fsn_mark;
     bool recalc;
     int ret = 0;
 
     fsnotify_group_lock(group);
     fsn_mark = fsnotify_find_mark(connp, group);
     if (!fsn_mark) {
         fsn_mark = fanotify_add_new_mark(group, connp, obj_type,
                          fan_flags, fsid);
         if (IS_ERR(fsn_mark)) {
             fsnotify_group_unlock(group);
             return PTR_ERR(fsn_mark);
         }
     }
 
     /*
      * Check if requested mark flags conflict with an existing mark flags.
      */
     ret = fanotify_may_update_existing_mark(fsn_mark, fan_flags);
     if (ret)
         goto out;
 
     /*
      * Error events are pre-allocated per group, only if strictly
      * needed (i.e. FAN_FS_ERROR was requested).
      */
     if (!(fan_flags & FANOTIFY_MARK_IGNORE_BITS) &&
         (mask & FAN_FS_ERROR)) {
         ret = fanotify_group_init_error_pool(group);
         if (ret)
             goto out;
     }
 
     recalc = fanotify_mark_add_to_mask(fsn_mark, mask, fan_flags);
     if (recalc)
         fsnotify_recalc_mask(fsn_mark->connector);
 
 out:
     fsnotify_group_unlock(group);
 
     fsnotify_put_mark(fsn_mark);
     return ret;
 }
 
 static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
                       struct vfsmount *mnt, __u32 mask,
                       unsigned int flags, __kernel_fsid_t *fsid)
 {
     return fanotify_add_mark(group, &real_mount(mnt)->mnt_fsnotify_marks,
                  FSNOTIFY_OBJ_TYPE_VFSMOUNT, mask, flags, fsid);
 }
 
 static int fanotify_add_sb_mark(struct fsnotify_group *group,
                 struct super_block *sb, __u32 mask,
                 unsigned int flags, __kernel_fsid_t *fsid)
 {
     return fanotify_add_mark(group, &sb->s_fsnotify_marks,
                  FSNOTIFY_OBJ_TYPE_SB, mask, flags, fsid);
 }
 
 static int fanotify_add_inode_mark(struct fsnotify_group *group,
                    struct inode *inode, __u32 mask,
                    unsigned int flags, __kernel_fsid_t *fsid)
 {
     pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
 
     /*
      * If some other task has this inode open for write we should not add
      * an ignore mask, unless that ignore mask is supposed to survive
      * modification changes anyway.
      */
     if ((flags & FANOTIFY_MARK_IGNORE_BITS) &&
         !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
         inode_is_open_for_write(inode))
         return 0;
 
     return fanotify_add_mark(group, &inode->i_fsnotify_marks,
                  FSNOTIFY_OBJ_TYPE_INODE, mask, flags, fsid);
 }
 
 static struct fsnotify_event *fanotify_alloc_overflow_event(void)
 {
     struct fanotify_event *oevent;
 
     oevent = kmalloc(sizeof(*oevent), GFP_KERNEL_ACCOUNT);
     if (!oevent)
         return NULL;
 
     fanotify_init_event(oevent, 0, FS_Q_OVERFLOW);
     oevent->type = FANOTIFY_EVENT_TYPE_OVERFLOW;
 
     return &oevent->fse;
 }
 
 static struct hlist_head *fanotify_alloc_merge_hash(void)
 {
     struct hlist_head *hash;
 
     hash = kmalloc(sizeof(struct hlist_head) << FANOTIFY_HTABLE_BITS,
                GFP_KERNEL_ACCOUNT);
     if (!hash)
         return NULL;
 
     __hash_init(hash, FANOTIFY_HTABLE_SIZE);
 
     return hash;
 }
 
 /* fanotify syscalls */
 SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 {
     struct fsnotify_group *group;
     int f_flags, fd;
     unsigned int fid_mode = flags & FANOTIFY_FID_BITS;
     unsigned int class = flags & FANOTIFY_CLASS_BITS;
     unsigned int internal_flags = 0;
 
     pr_debug("%s: flags=%x event_f_flags=%x\n",
          __func__, flags, event_f_flags);
 
     if (!capable(CAP_SYS_ADMIN)) {
         /*
          * An unprivileged user can setup an fanotify group with
          * limited functionality - an unprivileged group is limited to
          * notification events with file handles and it cannot use
          * unlimited queue/marks.
          */
         if ((flags & FANOTIFY_ADMIN_INIT_FLAGS) || !fid_mode)
             return -EPERM;
 
         /*
          * Setting the internal flag FANOTIFY_UNPRIV on the group
          * prevents setting mount/filesystem marks on this group and
          * prevents reporting pid and open fd in events.
          */
         internal_flags |= FANOTIFY_UNPRIV;
     }
 
 #ifdef CONFIG_AUDITSYSCALL
     if (flags & ~(FANOTIFY_INIT_FLAGS | FAN_ENABLE_AUDIT))
 #else
     if (flags & ~FANOTIFY_INIT_FLAGS)
 #endif
         return -EINVAL;
 
     /*
      * A pidfd can only be returned for a thread-group leader; thus
      * FAN_REPORT_PIDFD and FAN_REPORT_TID need to remain mutually
      * exclusive.
      */
     if ((flags & FAN_REPORT_PIDFD) && (flags & FAN_REPORT_TID))
         return -EINVAL;
 
     if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
         return -EINVAL;
 
     switch (event_f_flags & O_ACCMODE) {
     case O_RDONLY:
     case O_RDWR:
     case O_WRONLY:
         break;
     default:
         return -EINVAL;
     }
 
     if (fid_mode && class != FAN_CLASS_NOTIF)
         return -EINVAL;
 
     /*
      * Child name is reported with parent fid so requires dir fid.
      * We can report both child fid and dir fid with or without name.
      */
     if ((fid_mode & FAN_REPORT_NAME) && !(fid_mode & FAN_REPORT_DIR_FID))
         return -EINVAL;
 
     /*
      * FAN_REPORT_TARGET_FID requires FAN_REPORT_NAME and FAN_REPORT_FID
      * and is used as an indication to report both dir and child fid on all
      * dirent events.
      */
     if ((fid_mode & FAN_REPORT_TARGET_FID) &&
         (!(fid_mode & FAN_REPORT_NAME) || !(fid_mode & FAN_REPORT_FID)))
         return -EINVAL;
 
     f_flags = O_RDWR | __FMODE_NONOTIFY;
     if (flags & FAN_CLOEXEC)
         f_flags |= O_CLOEXEC;
     if (flags & FAN_NONBLOCK)
         f_flags |= O_NONBLOCK;
 
     /* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
     group = fsnotify_alloc_group(&fanotify_fsnotify_ops,
                      FSNOTIFY_GROUP_USER | FSNOTIFY_GROUP_NOFS);
     if (IS_ERR(group)) {
         return PTR_ERR(group);
     }
 
     /* Enforce groups limits per user in all containing user ns */
     group->fanotify_data.ucounts = inc_ucount(current_user_ns(),
                           current_euid(),
                           UCOUNT_FANOTIFY_GROUPS);
     if (!group->fanotify_data.ucounts) {
         fd = -EMFILE;
         goto out_destroy_group;
     }
 
     group->fanotify_data.flags = flags | internal_flags;
     group->memcg = get_mem_cgroup_from_mm(current->mm);
 
     group->fanotify_data.merge_hash = fanotify_alloc_merge_hash();
     if (!group->fanotify_data.merge_hash) {
         fd = -ENOMEM;
         goto out_destroy_group;
     }
 
     group->overflow_event = fanotify_alloc_overflow_event();
     if (unlikely(!group->overflow_event)) {
         fd = -ENOMEM;
         goto out_destroy_group;
     }
 
     if (force_o_largefile())
         event_f_flags |= O_LARGEFILE;
     group->fanotify_data.f_flags = event_f_flags;
     init_waitqueue_head(&group->fanotify_data.access_waitq);
     INIT_LIST_HEAD(&group->fanotify_data.access_list);
     switch (class) {
     case FAN_CLASS_NOTIF:
         group->priority = FS_PRIO_0;
         break;
     case FAN_CLASS_CONTENT:
         group->priority = FS_PRIO_1;
         break;
     case FAN_CLASS_PRE_CONTENT:
         group->priority = FS_PRIO_2;
         break;
     default:
         fd = -EINVAL;
         goto out_destroy_group;
     }
 
     if (flags & FAN_UNLIMITED_QUEUE) {
         fd = -EPERM;
         if (!capable(CAP_SYS_ADMIN))
             goto out_destroy_group;
         group->max_events = UINT_MAX;
     } else {
         group->max_events = fanotify_max_queued_events;
     }
 
     if (flags & FAN_UNLIMITED_MARKS) {
         fd = -EPERM;
         if (!capable(CAP_SYS_ADMIN))
             goto out_destroy_group;
     }
 
     if (flags & FAN_ENABLE_AUDIT) {
         fd = -EPERM;
         if (!capable(CAP_AUDIT_WRITE))
             goto out_destroy_group;
     }
 
     fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
     if (fd < 0)
         goto out_destroy_group;
 
     return fd;
 
 out_destroy_group:
     fsnotify_destroy_group(group);
     return fd;
 }
 
 static int fanotify_test_fsid(struct dentry *dentry, __kernel_fsid_t *fsid)
 {
     __kernel_fsid_t root_fsid;
     int err;
 
     /*
      * Make sure dentry is not of a filesystem with zero fsid (e.g. fuse).
      */
     err = vfs_get_fsid(dentry, fsid);
     if (err)
         return err;
 
     if (!fsid->val[0] && !fsid->val[1])
         return -ENODEV;
 
     /*
      * Make sure dentry is not of a filesystem subvolume (e.g. btrfs)
      * which uses a different fsid than sb root.
      */
     err = vfs_get_fsid(dentry->d_sb->s_root, &root_fsid);
     if (err)
         return err;
 
     if (root_fsid.val[0] != fsid->val[0] ||
         root_fsid.val[1] != fsid->val[1])
         return -EXDEV;
 
     return 0;
 }
 
 /* Check if filesystem can encode a unique fid */
 static int fanotify_test_fid(struct dentry *dentry)
 {
     /*
      * We need to make sure that the file system supports at least
      * encoding a file handle so user can use name_to_handle_at() to
      * compare fid returned with event to the file handle of watched
      * objects. However, name_to_handle_at() requires that the
      * filesystem also supports decoding file handles.
      */
     if (!dentry->d_sb->s_export_op ||
         !dentry->d_sb->s_export_op->fh_to_dentry)
         return -EOPNOTSUPP;
 
     return 0;
 }
 
 static int fanotify_events_supported(struct fsnotify_group *group,
                      struct path *path, __u64 mask,
                      unsigned int flags)
 {
     unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
     /* Strict validation of events in non-dir inode mask with v5.17+ APIs */
     bool strict_dir_events = FAN_GROUP_FLAG(group, FAN_REPORT_TARGET_FID) ||
                  (mask & FAN_RENAME) ||
                  (flags & FAN_MARK_IGNORE);
 
     /*
      * Some filesystems such as 'proc' acquire unusual locks when opening
      * files. For them fanotify permission events have high chances of
      * deadlocking the system - open done when reporting fanotify event
      * blocks on this "unusual" lock while another process holding the lock
      * waits for fanotify permission event to be answered. Just disallow
      * permission events for such filesystems.
      */
     if (mask & FANOTIFY_PERM_EVENTS &&
         path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)
         return -EINVAL;
 
     /*
      * We shouldn't have allowed setting dirent events and the directory
      * flags FAN_ONDIR and FAN_EVENT_ON_CHILD in mask of non-dir inode,
      * but because we always allowed it, error only when using new APIs.
      */
     if (strict_dir_events && mark_type == FAN_MARK_INODE &&
         !d_is_dir(path->dentry) && (mask & FANOTIFY_DIRONLY_EVENT_BITS))
         return -ENOTDIR;
 
     return 0;
 }
 
 static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
                 int dfd, const char  __user *pathname)
 {
     struct inode *inode = NULL;
     struct vfsmount *mnt = NULL;
     struct fsnotify_group *group;
     struct fd f;
     struct path path;
     __kernel_fsid_t __fsid, *fsid = NULL;
     u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS;
     unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
     unsigned int mark_cmd = flags & FANOTIFY_MARK_CMD_BITS;
     unsigned int ignore = flags & FANOTIFY_MARK_IGNORE_BITS;
     unsigned int obj_type, fid_mode;
     u32 umask = 0;
     int ret;
 
     pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
          __func__, fanotify_fd, flags, dfd, pathname, mask);
 
     /* we only use the lower 32 bits as of right now. */
     if (upper_32_bits(mask))
         return -EINVAL;
 
     if (flags & ~FANOTIFY_MARK_FLAGS)
         return -EINVAL;
 
     switch (mark_type) {
     case FAN_MARK_INODE:
         obj_type = FSNOTIFY_OBJ_TYPE_INODE;
         break;
     case FAN_MARK_MOUNT:
         obj_type = FSNOTIFY_OBJ_TYPE_VFSMOUNT;
         break;
     case FAN_MARK_FILESYSTEM:
         obj_type = FSNOTIFY_OBJ_TYPE_SB;
         break;
     default:
         return -EINVAL;
     }
 
     switch (mark_cmd) {
     case FAN_MARK_ADD:
     case FAN_MARK_REMOVE:
         if (!mask)
             return -EINVAL;
         break;
     case FAN_MARK_FLUSH:
         if (flags & ~(FANOTIFY_MARK_TYPE_BITS | FAN_MARK_FLUSH))
             return -EINVAL;
         break;
     default:
         return -EINVAL;
     }
 
     if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
         valid_mask |= FANOTIFY_PERM_EVENTS;
 
     if (mask & ~valid_mask)
         return -EINVAL;
 
 
     /* We don't allow FAN_MARK_IGNORE & FAN_MARK_IGNORED_MASK together */
     if (ignore == (FAN_MARK_IGNORE | FAN_MARK_IGNORED_MASK))
         return -EINVAL;
 
     /*
      * Event flags (FAN_ONDIR, FAN_EVENT_ON_CHILD) have no effect with
      * FAN_MARK_IGNORED_MASK.
      */
     if (ignore == FAN_MARK_IGNORED_MASK) {
         mask &= ~FANOTIFY_EVENT_FLAGS;
         umask = FANOTIFY_EVENT_FLAGS;
     }
 
     f = fdget(fanotify_fd);
     if (unlikely(!f.file))
         return -EBADF;
 
     /* verify that this is indeed an fanotify instance */
     ret = -EINVAL;
     if (unlikely(f.file->f_op != &fanotify_fops))
         goto fput_and_out;
     group = f.file->private_data;
 
     /*
      * An unprivileged user is not allowed to setup mount nor filesystem
      * marks.  This also includes setting up such marks by a group that
      * was initialized by an unprivileged user.
      */
     ret = -EPERM;
     if ((!capable(CAP_SYS_ADMIN) ||
          FAN_GROUP_FLAG(group, FANOTIFY_UNPRIV)) &&
         mark_type != FAN_MARK_INODE)
         goto fput_and_out;
 
     /*
      * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
      * allowed to set permissions events.
      */
     ret = -EINVAL;
     if (mask & FANOTIFY_PERM_EVENTS &&
         group->priority == FS_PRIO_0)
         goto fput_and_out;
 
     if (mask & FAN_FS_ERROR &&
         mark_type != FAN_MARK_FILESYSTEM)
         goto fput_and_out;
 
     /*
      * Evictable is only relevant for inode marks, because only inode object
      * can be evicted on memory pressure.
      */
     if (flags & FAN_MARK_EVICTABLE &&
          mark_type != FAN_MARK_INODE)
         goto fput_and_out;
 
     /*
      * Events that do not carry enough information to report
      * event->fd require a group that supports reporting fid.  Those
      * events are not supported on a mount mark, because they do not
      * carry enough information (i.e. path) to be filtered by mount
      * point.
      */
     fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);
     if (mask & ~(FANOTIFY_FD_EVENTS|FANOTIFY_EVENT_FLAGS) &&
         (!fid_mode || mark_type == FAN_MARK_MOUNT))
         goto fput_and_out;
 
     /*
      * FAN_RENAME uses special info type records to report the old and
      * new parent+name.  Reporting only old and new parent id is less
      * useful and was not implemented.
      */
     if (mask & FAN_RENAME && !(fid_mode & FAN_REPORT_NAME))
         goto fput_and_out;
 
     if (mark_cmd == FAN_MARK_FLUSH) {
         ret = 0;
         if (mark_type == FAN_MARK_MOUNT)
             fsnotify_clear_vfsmount_marks_by_group(group);
         else if (mark_type == FAN_MARK_FILESYSTEM)
             fsnotify_clear_sb_marks_by_group(group);
         else
             fsnotify_clear_inode_marks_by_group(group);
         goto fput_and_out;
     }
 
     ret = fanotify_find_path(dfd, pathname, &path, flags,
             (mask & ALL_FSNOTIFY_EVENTS), obj_type);
     if (ret)
         goto fput_and_out;
 
     if (mark_cmd == FAN_MARK_ADD) {
         ret = fanotify_events_supported(group, &path, mask, flags);
         if (ret)
             goto path_put_and_out;
     }
 
     if (fid_mode) {
         ret = fanotify_test_fsid(path.dentry, &__fsid);
         if (ret)
             goto path_put_and_out;
 
         ret = fanotify_test_fid(path.dentry);
         if (ret)
             goto path_put_and_out;
 
         fsid = &__fsid;
     }
 
     /* inode held in place by reference to path; group by fget on fd */
     if (mark_type == FAN_MARK_INODE)
         inode = path.dentry->d_inode;
     else
         mnt = path.mnt;
 
     ret = mnt ? -EINVAL : -EISDIR;
     /* FAN_MARK_IGNORE requires SURV_MODIFY for sb/mount/dir marks */
     if (mark_cmd == FAN_MARK_ADD && ignore == FAN_MARK_IGNORE &&
         (mnt || S_ISDIR(inode->i_mode)) &&
         !(flags & FAN_MARK_IGNORED_SURV_MODIFY))
         goto path_put_and_out;
 
     /* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */
     if (mnt || !S_ISDIR(inode->i_mode)) {
         mask &= ~FAN_EVENT_ON_CHILD;
         umask = FAN_EVENT_ON_CHILD;
         /*
          * If group needs to report parent fid, register for getting
          * events with parent/name info for non-directory.
          */
         if ((fid_mode & FAN_REPORT_DIR_FID) &&
             (flags & FAN_MARK_ADD) && !ignore)
             mask |= FAN_EVENT_ON_CHILD;
     }
 
     /* create/update an inode mark */
     switch (mark_cmd) {
     case FAN_MARK_ADD:
         if (mark_type == FAN_MARK_MOUNT)
             ret = fanotify_add_vfsmount_mark(group, mnt, mask,
                              flags, fsid);
         else if (mark_type == FAN_MARK_FILESYSTEM)
             ret = fanotify_add_sb_mark(group, mnt->mnt_sb, mask,
                            flags, fsid);
         else
             ret = fanotify_add_inode_mark(group, inode, mask,
                               flags, fsid);
         break;
     case FAN_MARK_REMOVE:
         if (mark_type == FAN_MARK_MOUNT)
             ret = fanotify_remove_vfsmount_mark(group, mnt, mask,
                                 flags, umask);
         else if (mark_type == FAN_MARK_FILESYSTEM)
             ret = fanotify_remove_sb_mark(group, mnt->mnt_sb, mask,
                               flags, umask);
         else
             ret = fanotify_remove_inode_mark(group, inode, mask,
                              flags, umask);
         break;
     default:
         ret = -EINVAL;
     }
 
 path_put_and_out:
     path_put(&path);
 fput_and_out:
     fdput(f);
     return ret;
 }
 
 #ifndef CONFIG_ARCH_SPLIT_ARG64
 SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
                   __u64, mask, int, dfd,
                   const char  __user *, pathname)
 {
     return do_fanotify_mark(fanotify_fd, flags, mask, dfd, pathname);
 }
 #endif
 
 #if defined(CONFIG_ARCH_SPLIT_ARG64) || defined(CONFIG_COMPAT)
 SYSCALL32_DEFINE6(fanotify_mark,
                 int, fanotify_fd, unsigned int, flags,
                 SC_ARG64(mask), int, dfd,
                 const char  __user *, pathname)
 {
     return do_fanotify_mark(fanotify_fd, flags, SC_VAL64(__u64, mask),
                 dfd, pathname);
 }
 #endif
 
 /*
  * fanotify_user_setup - Our initialization function.  Note that we cannot return
  * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
  * must result in panic().
  */
 static int __init fanotify_user_setup(void)
 {
     struct sysinfo si;
     int max_marks;
 
     si_meminfo(&si);
     /*
      * Allow up to 1% of addressable memory to be accounted for per user
      * marks limited to the range [8192, 1048576]. mount and sb marks are
      * a lot cheaper than inode marks, but there is no reason for a user
      * to have many of those, so calculate by the cost of inode marks.
      */
     max_marks = (((si.totalram - si.totalhigh) / 100) << PAGE_SHIFT) /
             INODE_MARK_COST;
     max_marks = clamp(max_marks, FANOTIFY_OLD_DEFAULT_MAX_MARKS,
                      FANOTIFY_DEFAULT_MAX_USER_MARKS);
 
     BUILD_BUG_ON(FANOTIFY_INIT_FLAGS & FANOTIFY_INTERNAL_GROUP_FLAGS);
     BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 12);
     BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 11);
 
     fanotify_mark_cache = KMEM_CACHE(fsnotify_mark,
                      SLAB_PANIC|SLAB_ACCOUNT);
     fanotify_fid_event_cachep = KMEM_CACHE(fanotify_fid_event,
                            SLAB_PANIC);
     fanotify_path_event_cachep = KMEM_CACHE(fanotify_path_event,
                         SLAB_PANIC);
     if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) {
         fanotify_perm_event_cachep =
             KMEM_CACHE(fanotify_perm_event, SLAB_PANIC);
     }
 
     fanotify_max_queued_events = FANOTIFY_DEFAULT_MAX_EVENTS;
     init_user_ns.ucount_max[UCOUNT_FANOTIFY_GROUPS] =
                     FANOTIFY_DEFAULT_MAX_GROUPS;
     init_user_ns.ucount_max[UCOUNT_FANOTIFY_MARKS] = max_marks;
     fanotify_sysctls_init();
 
     return 0;
 }
 device_initcall(fanotify_user_setup);

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