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#include <linux/fanotify.h>
#include <linux/fdtable.h>
#include <linux/fsnotify_backend.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/kernel.h> /* UINT_MAX */
#include <linux/mount.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/wait.h>
static bool should_merge(struct fsnotify_event *old, struct fsnotify_event *new)
{
pr_debug("%s: old=%p new=%p\n", __func__, old, new);
if (old->to_tell == new->to_tell &&
old->data_type == new->data_type &&
old->tgid == new->tgid) {
switch (old->data_type) {
case (FSNOTIFY_EVENT_FILE):
if ((old->file->f_path.mnt == new->file->f_path.mnt) &&
(old->file->f_path.dentry == new->file->f_path.dentry))
return true;
case (FSNOTIFY_EVENT_NONE):
return true;
default:
BUG();
};
}
return false;
}
/* and the list better be locked by something too! */
static struct fsnotify_event *fanotify_merge(struct list_head *list,
struct fsnotify_event *event)
{
struct fsnotify_event_holder *test_holder;
struct fsnotify_event *test_event = NULL;
struct fsnotify_event *new_event;
pr_debug("%s: list=%p event=%p\n", __func__, list, event);
list_for_each_entry_reverse(test_holder, list, event_list) {
if (should_merge(test_holder->event, event)) {
test_event = test_holder->event;
break;
}
}
if (!test_event)
return NULL;
fsnotify_get_event(test_event);
/* if they are exactly the same we are done */
if (test_event->mask == event->mask)
return test_event;
/*
* if the refcnt == 2 this is the only queue
* for this event and so we can update the mask
* in place.
*/
if (atomic_read(&test_event->refcnt) == 2) {
test_event->mask |= event->mask;
return test_event;
}
new_event = fsnotify_clone_event(test_event);
/* done with test_event */
fsnotify_put_event(test_event);
/* couldn't allocate memory, merge was not possible */
if (unlikely(!new_event))
return ERR_PTR(-ENOMEM);
/* build new event and replace it on the list */
new_event->mask = (test_event->mask | event->mask);
fsnotify_replace_event(test_holder, new_event);
/* we hold a reference on new_event from clone_event */
return new_event;
}
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
static int fanotify_get_response_from_access(struct fsnotify_group *group,
struct fsnotify_event *event)
{
int ret;
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
wait_event(group->fanotify_data.access_waitq, event->response);
/* userspace responded, convert to something usable */
spin_lock(&event->lock);
switch (event->response) {
case FAN_ALLOW:
ret = 0;
break;
case FAN_DENY:
default:
ret = -EPERM;
}
event->response = 0;
spin_unlock(&event->lock);
pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
group, event, ret);
return ret;
}
#endif
static int fanotify_handle_event(struct fsnotify_group *group,
struct fsnotify_mark *mark,
struct fsnotify_event *event)
{
int ret = 0;
struct fsnotify_event *notify_event = NULL;
BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
notify_event = fsnotify_add_notify_event(group, event, NULL, fanotify_merge);
if (IS_ERR(notify_event))
return PTR_ERR(notify_event);
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
if (event->mask & FAN_ALL_PERM_EVENTS) {
/* if we merged we need to wait on the new event */
if (notify_event)
event = notify_event;
ret = fanotify_get_response_from_access(group, event);
}
#endif
if (notify_event)
fsnotify_put_event(notify_event);
return ret;
}
static bool should_send_vfsmount_event(struct fsnotify_group *group, struct vfsmount *mnt,
struct inode *inode, __u32 mask)
{
struct fsnotify_mark *mnt_mark;
struct fsnotify_mark *inode_mark;
pr_debug("%s: group=%p vfsmount=%p mask=%x\n",
__func__, group, mnt, mask);
mnt_mark = fsnotify_find_vfsmount_mark(group, mnt);
if (!mnt_mark)
return false;
mask &= mnt_mark->mask;
mask &= ~mnt_mark->ignored_mask;
if (mask) {
inode_mark = fsnotify_find_inode_mark(group, inode);
if (inode_mark) {
mask &= ~inode_mark->ignored_mask;
fsnotify_put_mark(inode_mark);
}
}
/* find took a reference */
fsnotify_put_mark(mnt_mark);
return mask;
}
static bool should_send_inode_event(struct fsnotify_group *group, struct inode *inode,
__u32 mask)
{
struct fsnotify_mark *fsn_mark;
pr_debug("%s: group=%p inode=%p mask=%x\n",
__func__, group, inode, mask);
fsn_mark = fsnotify_find_inode_mark(group, inode);
if (!fsn_mark)
return false;
/* if the event is for a child and this inode doesn't care about
* events on the child, don't send it! */
if ((mask & FS_EVENT_ON_CHILD) &&
!(fsn_mark->mask & FS_EVENT_ON_CHILD)) {
mask = 0;
} else {
/*
* We care about children, but do we care about this particular
* type of event?
*/
mask &= ~FS_EVENT_ON_CHILD;
mask &= fsn_mark->mask;
mask &= ~fsn_mark->ignored_mask;
}
/* find took a reference */
fsnotify_put_mark(fsn_mark);
return mask;
}
static bool fanotify_should_send_event(struct fsnotify_group *group, struct inode *to_tell,
struct vfsmount *mnt, struct fsnotify_mark *mark,
__u32 mask, void *data, int data_type)
{
pr_debug("%s: group=%p to_tell=%p mnt=%p mask=%x data=%p data_type=%d\n",
__func__, group, to_tell, mnt, mask, data, data_type);
/* sorry, fanotify only gives a damn about files and dirs */
if (!S_ISREG(to_tell->i_mode) &&
!S_ISDIR(to_tell->i_mode))
return false;
/* if we don't have enough info to send an event to userspace say no */
if (data_type != FSNOTIFY_EVENT_FILE)
return false;
if (mnt)
return should_send_vfsmount_event(group, mnt, to_tell, mask);
else
return should_send_inode_event(group, to_tell, mask);
}
const struct fsnotify_ops fanotify_fsnotify_ops = {
.handle_event = fanotify_handle_event,
.should_send_event = fanotify_should_send_event,
.free_group_priv = NULL,
.free_event_priv = NULL,
.freeing_mark = NULL,
};
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