Commit 52c923dd authored by Eric Paris's avatar Eric Paris
Browse files

fanotify: fanotify_init syscall implementation

	fanotify_init - initialize an fanotify group

	int fanotify_init(unsigned int flags, unsigned int event_f_flags, int priority);

	fanotify_init() initializes a new fanotify instance and returns a file
	descriptor associated with the new fanotify event queue.

	The following values can be OR'd into the flags field:

	FAN_NONBLOCK Set the O_NONBLOCK file status flag on the new open file description.
		Using this flag saves extra calls to fcntl(2) to achieve the same

	FAN_CLOEXEC Set the close-on-exec (FD_CLOEXEC) flag on the new file descriptor.
		See the description of the O_CLOEXEC flag in open(2) for reasons why
		this may be useful.

	The event_f_flags argument is unused and must be set to 0

	The priority argument is unused and must be set to 0

	On success, this system call return a new file descriptor. On error, -1 is
	returned, and errno is set to indicate the error.

	EINVAL An invalid value was specified in flags.

	EINVAL A non-zero valid was passed in event_f_flags or in priority

	ENFILE The system limit on the total number of file descriptors has been reached.

	ENOMEM Insufficient kernel memory is available.

	These system calls are Linux-specific.
Signed-off-by: default avatarEric Paris <>
parent 11637e4b
......@@ -4,6 +4,8 @@
#include <linux/kernel.h>
#include <linux/types.h>
extern const struct fsnotify_ops fanotify_fsnotify_ops;
static inline bool fanotify_mask_valid(__u32 mask)
if (mask & ~((__u32)FAN_ALL_INCOMING_EVENTS))
#include <linux/fcntl.h>
#include <linux/fs.h>
#include <linux/anon_inodes.h>
#include <linux/fsnotify_backend.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include "fanotify.h"
static int fanotify_release(struct inode *ignored, struct file *file)
struct fsnotify_group *group = file->private_data;
pr_debug("%s: file=%p group=%p\n", __func__, file, group);
/* matches the fanotify_init->fsnotify_alloc_group */
return 0;
static const struct file_operations fanotify_fops = {
.poll = NULL,
.read = NULL,
.fasync = NULL,
.release = fanotify_release,
.unlocked_ioctl = NULL,
.compat_ioctl = NULL,
/* fanotify syscalls */
SYSCALL_DEFINE3(fanotify_init, unsigned int, flags, unsigned int, event_f_flags,
unsigned int, priority)
return -ENOSYS;
struct fsnotify_group *group;
int f_flags, fd;
pr_debug("%s: flags=%d event_f_flags=%d priority=%d\n",
__func__, flags, event_f_flags, priority);
if (event_f_flags)
return -EINVAL;
if (priority)
return -EINVAL;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
if (flags & ~FAN_ALL_INIT_FLAGS)
return -EINVAL;
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);
if (IS_ERR(group))
return PTR_ERR(group);
fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
if (fd < 0)
goto out_put_group;
return fd;
return fd;
......@@ -18,6 +18,10 @@
/* helper events */
#define FAN_CLOEXEC 0x00000001
#define FAN_NONBLOCK 0x00000002
* All of the events - we build the list by hand so that we can add flags in
* the future and not break backward compatibility. Apps will get only the
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