fanotify_mark(2) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | BUGS | SEE ALSO | COLOPHON

FANOTIFY_MARK(2)        Linux Programmer's Manual       FANOTIFY_MARK(2)

NAME         top

       fanotify_mark - add, remove, or modify an fanotify mark on a
       filesystem object

SYNOPSIS         top

       #include <sys/fanotify.h>

       int fanotify_mark(int fanotify_fd, unsigned int flags,
                         uint64_t mask, int dirfd, const char *pathname);

DESCRIPTION         top

       For an overview of the fanotify API, see fanotify(7).

       fanotify_mark() adds, removes, or modifies an fanotify mark on a
       filesystem object.  The caller must have read permission on the
       filesystem object that is to be marked.

       The fanotify_fd argument is a file descriptor returned by
       fanotify_init(2).

       flags is a bit mask describing the modification to perform.  It
       must include exactly one of the following values:

       FAN_MARK_ADD
              The events in mask will be added to the mark mask (or to
              the ignore mask).  mask must be nonempty or the error
              EINVAL will occur.

       FAN_MARK_REMOVE
              The events in argument mask will be removed from the mark
              mask (or from the ignore mask).  mask must be nonempty or
              the error EINVAL will occur.

       FAN_MARK_FLUSH
              Remove either all marks for filesystems, all marks for
              mounts, or all marks for directories and files from the
              fanotify group.  If flags contains FAN_MARK_MOUNT, all
              marks for mounts are removed from the group.  If flags
              contains FAN_MARK_FILESYSTEM, all marks for filesystems
              are removed from the group.  Otherwise, all marks for
              directories and files are removed.  No flag other than,
              and at most one of, the flags FAN_MARK_MOUNT or
              FAN_MARK_FILESYSTEM can be used in conjunction with
              FAN_MARK_FLUSH.  mask is ignored.

       If none of the values above is specified, or more than one is
       specified, the call fails with the error EINVAL.

       In addition, zero or more of the following values may be ORed
       into flags:

       FAN_MARK_DONT_FOLLOW
              If pathname is a symbolic link, mark the link itself,
              rather than the file to which it refers.  (By default,
              fanotify_mark() dereferences pathname if it is a symbolic
              link.)

       FAN_MARK_ONLYDIR
              If the filesystem object to be marked is not a directory,
              the error ENOTDIR shall be raised.

       FAN_MARK_MOUNT
              Mark the mount specified by pathname.  If pathname is not
              itself a mount point, the mount containing pathname will
              be marked.  All directories, subdirectories, and the
              contained files of the mount will be monitored.  The
              events which require that filesystem objects are
              identified by file handles, such as FAN_CREATE,
              FAN_ATTRIB, FAN_MOVE, and FAN_DELETE_SELF, cannot be
              provided as a mask when flags contains FAN_MARK_MOUNT.
              Attempting to do so will result in the error EINVAL being
              returned.

       FAN_MARK_FILESYSTEM (since Linux 4.20)
              Mark the filesystem specified by pathname.  The filesystem
              containing pathname will be marked.  All the contained
              files and directories of the filesystem from any mount
              point will be monitored.

       FAN_MARK_IGNORED_MASK
              The events in mask shall be added to or removed from the
              ignore mask.

       FAN_MARK_IGNORED_SURV_MODIFY
              The ignore mask shall survive modify events.  If this flag
              is not set, the ignore mask is cleared when a modify event
              occurs for the ignored file or directory.

       mask defines which events shall be listened for (or which shall
       be ignored).  It is a bit mask composed of the following values:

       FAN_ACCESS
              Create an event when a file or directory (but see BUGS) is
              accessed (read).

       FAN_MODIFY
              Create an event when a file is modified (write).

       FAN_CLOSE_WRITE
              Create an event when a writable file is closed.

       FAN_CLOSE_NOWRITE
              Create an event when a read-only file or directory is
              closed.

       FAN_OPEN
              Create an event when a file or directory is opened.

       FAN_OPEN_EXEC (since Linux 5.0)
              Create an event when a file is opened with the intent to
              be executed.  See NOTES for additional details.

       FAN_ATTRIB (since Linux 5.1)
              Create an event when the metadata for a file or directory
              has changed.  An fanotify group that identifies filesystem
              objects by file handles is required.

       FAN_CREATE (since Linux 5.1)
              Create an event when a file or directory has been created
              in a marked parent directory.  An fanotify group that
              identifies filesystem objects by file handles is required.

       FAN_DELETE (since Linux 5.1)
              Create an event when a file or directory has been deleted
              in a marked parent directory.  An fanotify group that
              identifies filesystem objects by file handles is required.

       FAN_DELETE_SELF (since Linux 5.1)
              Create an event when a marked file or directory itself is
              deleted.  An fanotify group that identifies filesystem
              objects by file handles is required.

       FAN_MOVED_FROM (since Linux 5.1)
              Create an event when a file or directory has been moved
              from a marked parent directory.  An fanotify group that
              identifies filesystem objects by file handles is required.

       FAN_MOVED_TO (since Linux 5.1)
              Create an event when a file or directory has been moved to
              a marked parent directory.  An fanotify group that
              identifies filesystem objects by file handles is required.

       FAN_MOVE_SELF (since Linux 5.1)
              Create an event when a marked file or directory itself has
              been moved.  An fanotify group that identifies filesystem
              objects by file handles is required.

       FAN_OPEN_PERM
              Create an event when a permission to open a file or
              directory is requested.  An fanotify file descriptor
              created with FAN_CLASS_PRE_CONTENT or FAN_CLASS_CONTENT is
              required.

       FAN_OPEN_EXEC_PERM (since Linux 5.0)
              Create an event when a permission to open a file for
              execution is requested.  An fanotify file descriptor
              created with FAN_CLASS_PRE_CONTENT or FAN_CLASS_CONTENT is
              required.  See NOTES for additional details.

       FAN_ACCESS_PERM
              Create an event when a permission to read a file or
              directory is requested.  An fanotify file descriptor
              created with FAN_CLASS_PRE_CONTENT or FAN_CLASS_CONTENT is
              required.

       FAN_ONDIR
              Create events for directories—for example, when
              opendir(3), readdir(3) (but see BUGS), and closedir(3) are
              called.  Without this flag, events are created only for
              files.  In the context of directory entry events, such as
              FAN_CREATE, FAN_DELETE, FAN_MOVED_FROM, and FAN_MOVED_TO,
              specifying the flag FAN_ONDIR is required in order to
              create events when subdirectory entries are modified
              (i.e., mkdir(2)/ rmdir(2)).

       FAN_EVENT_ON_CHILD
              Events for the immediate children of marked directories
              shall be created.  The flag has no effect when marking
              mounts and filesystems.  Note that events are not
              generated for children of the subdirectories of marked
              directories.  More specifically, the directory entry
              modification events FAN_CREATE, FAN_DELETE,
              FAN_MOVED_FROM, and FAN_MOVED_TO are not generated for any
              entry modifications performed inside subdirectories of
              marked directories.  Note that the events FAN_DELETE_SELF
              and FAN_MOVE_SELF are not generated for children of marked
              directories.  To monitor complete directory trees it is
              necessary to mark the relevant mount or filesystem.

       The following composed values are defined:

       FAN_CLOSE
              A file is closed (FAN_CLOSE_WRITE|FAN_CLOSE_NOWRITE).

       FAN_MOVE
              A file or directory has been moved
              (FAN_MOVED_FROM|FAN_MOVED_TO).

       The filesystem object to be marked is determined by the file
       descriptor dirfd and the pathname specified in pathname:

       *  If pathname is NULL, dirfd defines the filesystem object to be
          marked.

       *  If pathname is NULL, and dirfd takes the special value
          AT_FDCWD, the current working directory is to be marked.

       *  If pathname is absolute, it defines the filesystem object to
          be marked, and dirfd is ignored.

       *  If pathname is relative, and dirfd does not have the value
          AT_FDCWD, then the filesystem object to be marked is
          determined by interpreting pathname relative the directory
          referred to by dirfd.

       *  If pathname is relative, and dirfd has the value AT_FDCWD,
          then the filesystem object to be marked is determined by
          interpreting pathname relative to the current working
          directory.  (See openat(2) for an explanation of why the dirfd
          argument is useful.)

RETURN VALUE         top

       On success, fanotify_mark() returns 0.  On error, -1 is returned,
       and errno is set to indicate the error.

ERRORS         top

       EBADF  An invalid file descriptor was passed in fanotify_fd.

       EBADF  pathname is relative but dirfd is neither AT_FDCWD nor a
              valid file descriptor.

       EINVAL An invalid value was passed in flags or mask, or
              fanotify_fd was not an fanotify file descriptor.

       EINVAL The fanotify file descriptor was opened with
              FAN_CLASS_NOTIF or the fanotify group identifies
              filesystem objects by file handles and mask contains a
              flag for permission events (FAN_OPEN_PERM or
              FAN_ACCESS_PERM).

       ENODEV The filesystem object indicated by pathname is not
              associated with a filesystem that supports fsid (e.g.,
              tmpfs(5)).  This error can be returned only with an
              fanotify group that identifies filesystem objects by file
              handles.

       ENOENT The filesystem object indicated by dirfd and pathname does
              not exist.  This error also occurs when trying to remove a
              mark from an object which is not marked.

       ENOMEM The necessary memory could not be allocated.

       ENOSPC The number of marks exceeds the limit of 8192 and the
              FAN_UNLIMITED_MARKS flag was not specified when the
              fanotify file descriptor was created with
              fanotify_init(2).

       ENOSYS This kernel does not implement fanotify_mark().  The
              fanotify API is available only if the kernel was
              configured with CONFIG_FANOTIFY.

       ENOTDIR
              flags contains FAN_MARK_ONLYDIR, and dirfd and pathname do
              not specify a directory.

       EOPNOTSUPP
              The object indicated by pathname is associated with a
              filesystem that does not support the encoding of file
              handles.  This error can be returned only with an fanotify
              group that identifies filesystem objects by file handles.

       EXDEV  The filesystem object indicated by pathname resides within
              a filesystem subvolume (e.g., btrfs(5)) which uses a
              different fsid than its root superblock.  This error can
              be returned only with an fanotify group that identifies
              filesystem objects by file handles.

VERSIONS         top

       fanotify_mark() was introduced in version 2.6.36 of the Linux
       kernel and enabled in version 2.6.37.

CONFORMING TO         top

       This system call is Linux-specific.

NOTES         top

   FAN_OPEN_EXEC and FAN_OPEN_EXEC_PERM
       When using either FAN_OPEN_EXEC or FAN_OPEN_EXEC_PERM within the
       mask, events of these types will be returned only when the direct
       execution of a program occurs.  More specifically, this means
       that events of these types will be generated for files that are
       opened using execve(2), execveat(2), or uselib(2).  Events of
       these types will not be raised in the situation where an
       interpreter is passed (or reads) a file for interpretation.

       Additionally, if a mark has also been placed on the Linux dynamic
       linker, a user should also expect to receive an event for it when
       an ELF object has been successfully opened using execve(2) or
       execveat(2).

       For example, if the following ELF binary were to be invoked and a
       FAN_OPEN_EXEC mark has been placed on /:

           $ /bin/echo foo

       The listening application in this case would receive
       FAN_OPEN_EXEC events for both the ELF binary and interpreter,
       respectively:

           /bin/echo
           /lib64/ld-linux-x86-64.so.2

BUGS         top

       The following bugs were present in Linux kernels before version
       3.16:

       *  If flags contains FAN_MARK_FLUSH, dirfd, and pathname must
          specify a valid filesystem object, even though this object is
          not used.

       *  readdir(2) does not generate a FAN_ACCESS event.

       *  If fanotify_mark() is called with FAN_MARK_FLUSH, flags is not
          checked for invalid values.

SEE ALSO         top

       fanotify_init(2), fanotify(7)

COLOPHON         top

       This page is part of release 5.13 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                          2021-08-27               FANOTIFY_MARK(2)

Pages that refer to this page: fanotify_init(2)open(2)syscalls(2)proc(5)fanotify(7)