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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | STANDARDS | HISTORY | NOTES | BUGS | SEE ALSO | COLOPHON |
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fanotify_mark(2) System Calls Manual fanotify_mark(2)
fanotify_mark - add, remove, or modify an fanotify mark on a
filesystem object
Standard C library (libc, -lc)
#include <sys/fanotify.h>
int fanotify_mark(int fanotify_fd, unsigned int flags,
uint64_t mask, int dirfd,
const char *_Nullable pathname);
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. Use of this flag requires the CAP_SYS_ADMIN
capability.
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. Use of this flag requires the
CAP_SYS_ADMIN capability.
FAN_MARK_IGNORED_MASK
The events in mask shall be added to or removed from the
ignore mask. Note that the flags FAN_ONDIR, and
FAN_EVENT_ON_CHILD have no effect when provided with this
flag. The effect of setting the flags FAN_ONDIR, and
FAN_EVENT_ON_CHILD in the mark mask on the events that are
set in the ignore mask is undefined and depends on the
Linux kernel version. Specifically, prior to Linux 5.9,
setting a mark mask on a file and a mark with ignore mask
on its parent directory would not result in ignoring
events on the file, regardless of the FAN_EVENT_ON_CHILD
flag in the parent directory's mark mask. When the ignore
mask is updated with the FAN_MARK_IGNORED_MASK flag on a
mark that was previously updated with the FAN_MARK_IGNORE
flag, the update fails with EEXIST error.
FAN_MARK_IGNORE (since Linux 6.0)
This flag has a similar effect as setting the
FAN_MARK_IGNORED_MASK flag. The events in mask shall be
added to or removed from the ignore mask. Unlike the
FAN_MARK_IGNORED_MASK flag, this flag also has the effect
that the FAN_ONDIR, and FAN_EVENT_ON_CHILD flags take
effect on the ignore mask. Specifically, unless the
FAN_ONDIR flag is set with FAN_MARK_IGNORE, events on
directories will not be ignored. If the flag
FAN_EVENT_ON_CHILD is set with FAN_MARK_IGNORE, events on
children will be ignored. For example, a mark on a
directory with combination of a mask with FAN_CREATE event
and FAN_ONDIR flag and an ignore mask with FAN_CREATE
event and without FAN_ONDIR flag, will result in getting
only the events for creation of sub-directories. When
using the FAN_MARK_IGNORE flag to add to an ignore mask of
a mount, filesystem, or directory inode mark, the
FAN_MARK_IGNORED_SURV_MODIFY flag must be specified.
Failure to do so will results with EINVAL or EISDIR error.
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 on the marked object. Omitting this flag is
typically used to suppress events (e.g., FAN_OPEN) for a
specific file, until that specific file's content has been
modified. It is far less useful to suppress events on an
entire filesystem, or mount, or on all files inside a
directory, until some file's content has been modified.
For this reason, the FAN_MARK_IGNORE flag requires the
FAN_MARK_IGNORED_SURV_MODIFY flag on a mount, filesystem,
or directory inode mark. This flag cannot be removed from
a mark once set. When the ignore mask is updated without
this flag on a mark that was previously updated with the
FAN_MARK_IGNORE and FAN_MARK_IGNORED_SURV_MODIFY flags,
the update fails with EEXIST error.
FAN_MARK_IGNORE_SURV
This is a synonym for
(FAN_MARK_IGNORE|FAN_MARK_IGNORED_SURV_MODIFY).
FAN_MARK_EVICTABLE (since Linux 5.19)
When an inode mark is created with this flag, the inode
object will not be pinned to the inode cache, therefore,
allowing the inode object to be evicted from the inode
cache when the memory pressure on the system is high. The
eviction of the inode object results in the evictable mark
also being lost. When the mask of an evictable inode mark
is updated without using the FAN_MARK_EVICATBLE flag, the
marked inode is pinned to inode cache and the mark is no
longer evictable. When the mask of a non-evictable inode
mark is updated with the FAN_MARK_EVICTABLE flag, the
inode mark remains non-evictable and the update fails with
EEXIST error. Mounts and filesystems are not evictable
objects, therefore, an attempt to create a mount mark or a
filesystem mark with the FAN_MARK_EVICTABLE flag, will
result in the error EINVAL. For example, inode marks can
be used in combination with mount marks to reduce the
amount of events from noninteresting paths. The event
listener reads events, checks if the path reported in the
event is of interest, and if it is not, the listener sets
a mark with an ignore mask on the directory. Evictable
inode marks allow using this method for a large number of
directories without the concern of pinning all inodes and
exhausting the system's memory.
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_FS_ERROR (since Linux 5.16)
Create an event when a filesystem error leading to
inconsistent filesystem metadata is detected. An
additional information record of type
FAN_EVENT_INFO_TYPE_ERROR is returned for each event in
the read buffer. An fanotify group that identifies
filesystem objects by file handles is required.
Events of such type are dependent on support from the
underlying filesystem. At the time of writing, only the
ext4 filesystem reports FAN_FS_ERROR events.
See fanotify(7) for additional details.
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_RENAME (since Linux 5.17)
This event contains the same information provided by
events FAN_MOVED_FROM and FAN_MOVED_TO, however is
represented by a single event with up to two information
records. An fanotify group that identifies filesystem
objects by file handles is required. If the filesystem
object to be marked is not a directory, the error ENOTDIR
shall be raised.
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.)
On success, fanotify_mark() returns 0. On error, -1 is returned,
and errno is set to indicate the error.
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.
EEXIST The filesystem object indicated by dirfd and pathname has
a mark that was updated without the FAN_MARK_EVICTABLE
flag, and the user attempted to update the mark with
FAN_MARK_EVICTABLE flag.
EEXIST The filesystem object indicated by dirfd and pathname has
a mark that was updated with the FAN_MARK_IGNORE flag, and
the user attempted to update the mark with
FAN_MARK_IGNORED_MASK flag.
EEXIST The filesystem object indicated by dirfd and pathname has
a mark that was updated with the FAN_MARK_IGNORE and
FAN_MARK_IGNORED_SURV_MODIFY flags, and the user attempted
to update the mark only with FAN_MARK_IGNORE flag.
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).
EINVAL The group was initialized without FAN_REPORT_FID but one
or more event types specified in the mask require it.
EINVAL flags contains FAN_MARK_IGNORE, and either FAN_MARK_MOUNT
or FAN_MARK_FILESYSTEM, but does not contain
FAN_MARK_IGNORED_SURV_MODIFY.
EISDIR flags contains FAN_MARK_IGNORE, but does not contain
FAN_MARK_IGNORED_SURV_MODIFY, and dirfd and pathname
specify a directory.
ENODEV The filesystem object indicated by dirfd and pathname is
not associated with a filesystem that supports fsid (e.g.,
fuse(4)). tmpfs(5) did not support fsid prior to Linux
5.13. 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 for this user exceeds the limit and
the FAN_UNLIMITED_MARKS flag was not specified when the
fanotify file descriptor was created with
fanotify_init(2). See fanotify(7) for details about this
limit.
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.
ENOTDIR
mask contains FAN_RENAME, and dirfd and pathname do not
specify a directory.
ENOTDIR
flags contains FAN_MARK_IGNORE, or the fanotify group was
initialized with flag FAN_REPORT_TARGET_FID, and mask
contains directory entry modification events (e.g.,
FAN_CREATE, FAN_DELETE), or directory event flags (e.g.,
FAN_ONDIR, FAN_EVENT_ON_CHILD), 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.
Calling name_to_handle_at(2) with the flag AT_HANDLE_FID
(since Linux 6.5) can be used as a test to check if a
filesystem supports reporting events with file handles.
EPERM The operation is not permitted because the caller lacks a
required capability.
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.
Linux.
Linux 2.6.37.
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
The following bugs were present in before Linux 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.
fanotify_init(2), fanotify(7)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Linux man-pages 6.9.1 2024-05-02 fanotify_mark(2)
Pages that refer to this page: fanotify_init(2), open(2), syscalls(2), proc_pid_fdinfo(5), fanotify(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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