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#include <linux/fanotify.h>
#include <linux/fdtable.h>
#include <linux/fsnotify_backend.h>
#include <linux/init.h>
#include <linux/kernel.h> /* UINT_MAX */
#include <linux/mount.h>
#include <linux/types.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_PATH):
if ((old->path.mnt == new->path.mnt) &&
(old->path.dentry == new->path.dentry))
return true;
case (FSNOTIFY_EVENT_NONE):
return true;
default:
BUG();
};
}
return false;
}
/* Note, if we return an event in *arg that a reference is being held... */
static int fanotify_merge(struct list_head *list,
struct fsnotify_event *event,
void **arg)
{
struct fsnotify_event_holder *test_holder;
struct fsnotify_event *test_event;
struct fsnotify_event *new_event;
struct fsnotify_event **return_event = (struct fsnotify_event **)arg;
int ret = 0;
pr_debug("%s: list=%p event=%p\n", __func__, list, event);
*return_event = NULL;
/* and the list better be locked by something too! */
list_for_each_entry_reverse(test_holder, list, event_list) {
test_event = test_holder->event;
if (should_merge(test_event, event)) {
fsnotify_get_event(test_event);
*return_event = test_event;
ret = -EEXIST;
/* if they are exactly the same we are done */
if (test_event->mask == event->mask)
goto out;
/*
* if the refcnt == 1 this is the only queue
* for this event and so we can update the mask
* in place.
*/
if (atomic_read(&test_event->refcnt) == 1) {
test_event->mask |= event->mask;
goto out;
}
/* can't allocate memory, merge was no possible */
new_event = fsnotify_clone_event(test_event);
if (unlikely(!new_event)) {
ret = 0;
goto out;
}
/* we didn't return the test_event, so drop that ref */
fsnotify_put_event(test_event);
/* the reference we return on new_event is from clone */
*return_event = new_event;
/* build new event and replace it on the list */
new_event->mask = (test_event->mask | event->mask);
fsnotify_replace_event(test_holder, new_event);
break;
}
}
out:
return ret;
}
static int fanotify_handle_event(struct fsnotify_group *group, struct fsnotify_event *event)
{
int ret;
struct fsnotify_event *used_event;
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);
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
ret = fsnotify_add_notify_event(group, event, NULL, fanotify_merge, (void **)&used_event);
/* -EEXIST means this event was merged with another, not that it was an error */
if (ret == -EEXIST)
ret = 0;
if (used_event)
fsnotify_put_event(used_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, __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_PATH)
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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