fanotify: send events using read
Send events to userspace by reading the file descriptor from fanotify_init().
One will get blocks of data which look like:
struct fanotify_event_metadata {
__u32 event_len;
__u32 vers;
__s32 fd;
__u64 mask;
__s64 pid;
__u64 cookie;
} __attribute__ ((packed));
Simple code to retrieve and deal with events is below
while ((len = read(fan_fd, buf, sizeof(buf))) > 0) {
struct fanotify_event_metadata *metadata;
metadata = (void *)buf;
while(FAN_EVENT_OK(metadata, len)) {
[PROCESS HERE!!]
if (metadata->fd >= 0 && close(metadata->fd) != 0)
goto fail;
metadata = FAN_EVENT_NEXT(metadata, len);
}
}
Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index bc4fa48..a99550f 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -4,15 +4,202 @@
#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/types.h>
+#include <linux/uaccess.h>
+
+#include <asm/ioctls.h>
#include "fanotify.h"
static struct kmem_cache *fanotify_mark_cache __read_mostly;
+/*
+ * Get an fsnotify notification event if one exists and is small
+ * enough to fit in "count". Return an error pointer if the count
+ * is not large enough.
+ *
+ * Called with the group->notification_mutex held.
+ */
+static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
+ size_t count)
+{
+ BUG_ON(!mutex_is_locked(&group->notification_mutex));
+
+ pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
+
+ if (fsnotify_notify_queue_is_empty(group))
+ return NULL;
+
+ if (FAN_EVENT_METADATA_LEN > count)
+ return ERR_PTR(-EINVAL);
+
+ /* held the notification_mutex the whole time, so this is the
+ * same event we peeked above */
+ return fsnotify_remove_notify_event(group);
+}
+
+static int create_and_fill_fd(struct fsnotify_group *group,
+ struct fanotify_event_metadata *metadata,
+ struct fsnotify_event *event)
+{
+ int client_fd;
+ struct dentry *dentry;
+ struct vfsmount *mnt;
+ struct file *new_file;
+
+ pr_debug("%s: group=%p metadata=%p event=%p\n", __func__, group,
+ metadata, event);
+
+ client_fd = get_unused_fd();
+ if (client_fd < 0)
+ return client_fd;
+
+ if (event->data_type != FSNOTIFY_EVENT_PATH) {
+ WARN_ON(1);
+ put_unused_fd(client_fd);
+ return -EINVAL;
+ }
+
+ /*
+ * we need a new file handle for the userspace program so it can read even if it was
+ * originally opened O_WRONLY.
+ */
+ dentry = dget(event->path.dentry);
+ mnt = mntget(event->path.mnt);
+ /* it's possible this event was an overflow event. in that case dentry and mnt
+ * are NULL; That's fine, just don't call dentry open */
+ if (dentry && mnt)
+ new_file = dentry_open(dentry, mnt,
+ O_RDONLY | O_LARGEFILE | FMODE_NONOTIFY,
+ current_cred());
+ else
+ new_file = ERR_PTR(-EOVERFLOW);
+ 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 {
+ fd_install(client_fd, new_file);
+ }
+
+ metadata->fd = client_fd;
+
+ return 0;
+}
+
+static ssize_t fill_event_metadata(struct fsnotify_group *group,
+ struct fanotify_event_metadata *metadata,
+ struct fsnotify_event *event)
+{
+ pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
+ group, metadata, event);
+
+ metadata->event_len = FAN_EVENT_METADATA_LEN;
+ metadata->vers = FANOTIFY_METADATA_VERSION;
+ metadata->mask = fanotify_outgoing_mask(event->mask);
+
+ return create_and_fill_fd(group, metadata, event);
+
+}
+
+static ssize_t copy_event_to_user(struct fsnotify_group *group,
+ struct fsnotify_event *event,
+ char __user *buf)
+{
+ struct fanotify_event_metadata fanotify_event_metadata;
+ int ret;
+
+ pr_debug("%s: group=%p event=%p\n", __func__, group, event);
+
+ ret = fill_event_metadata(group, &fanotify_event_metadata, event);
+ if (ret)
+ return ret;
+
+ if (copy_to_user(buf, &fanotify_event_metadata, FAN_EVENT_METADATA_LEN))
+ return -EFAULT;
+
+ return FAN_EVENT_METADATA_LEN;
+}
+
+/* intofiy userspace file descriptor functions */
+static unsigned int fanotify_poll(struct file *file, poll_table *wait)
+{
+ struct fsnotify_group *group = file->private_data;
+ int ret = 0;
+
+ poll_wait(file, &group->notification_waitq, wait);
+ mutex_lock(&group->notification_mutex);
+ if (!fsnotify_notify_queue_is_empty(group))
+ ret = POLLIN | POLLRDNORM;
+ mutex_unlock(&group->notification_mutex);
+
+ return ret;
+}
+
+static ssize_t fanotify_read(struct file *file, char __user *buf,
+ size_t count, loff_t *pos)
+{
+ struct fsnotify_group *group;
+ struct fsnotify_event *kevent;
+ char __user *start;
+ int ret;
+ DEFINE_WAIT(wait);
+
+ start = buf;
+ group = file->private_data;
+
+ pr_debug("%s: group=%p\n", __func__, group);
+
+ while (1) {
+ prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE);
+
+ mutex_lock(&group->notification_mutex);
+ kevent = get_one_event(group, count);
+ mutex_unlock(&group->notification_mutex);
+
+ if (kevent) {
+ ret = PTR_ERR(kevent);
+ if (IS_ERR(kevent))
+ break;
+ ret = copy_event_to_user(group, kevent, buf);
+ fsnotify_put_event(kevent);
+ if (ret < 0)
+ break;
+ buf += ret;
+ count -= ret;
+ continue;
+ }
+
+ ret = -EAGAIN;
+ if (file->f_flags & O_NONBLOCK)
+ break;
+ ret = -EINTR;
+ if (signal_pending(current))
+ break;
+
+ if (start != buf)
+ break;
+
+ schedule();
+ }
+
+ finish_wait(&group->notification_waitq, &wait);
+ if (start != buf && ret != -EFAULT)
+ ret = buf - start;
+ return ret;
+}
+
static int fanotify_release(struct inode *ignored, struct file *file)
{
struct fsnotify_group *group = file->private_data;
@@ -25,13 +212,38 @@
return 0;
}
+static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ struct fsnotify_group *group;
+ struct fsnotify_event_holder *holder;
+ void __user *p;
+ int ret = -ENOTTY;
+ size_t send_len = 0;
+
+ group = file->private_data;
+
+ p = (void __user *) arg;
+
+ switch (cmd) {
+ case FIONREAD:
+ mutex_lock(&group->notification_mutex);
+ list_for_each_entry(holder, &group->notification_list, event_list)
+ send_len += FAN_EVENT_METADATA_LEN;
+ mutex_unlock(&group->notification_mutex);
+ ret = put_user(send_len, (int __user *) p);
+ break;
+ }
+
+ return ret;
+}
+
static const struct file_operations fanotify_fops = {
- .poll = NULL,
- .read = NULL,
+ .poll = fanotify_poll,
+ .read = fanotify_read,
.fasync = NULL,
.release = fanotify_release,
- .unlocked_ioctl = NULL,
- .compat_ioctl = NULL,
+ .unlocked_ioctl = fanotify_ioctl,
+ .compat_ioctl = fanotify_ioctl,
};
static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)