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

NAME

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

SYNOPSIS

       #include <sys/fanotify.h>

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

DESCRIPTION

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

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

ERRORS

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

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

CONFORMING TO

       This system call is Linux-specific.

NOTES

   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

       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.

COLOPHON

       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/.