502 строки
14 KiB
C
502 строки
14 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/fanotify.h>
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#include <linux/fdtable.h>
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#include <linux/fsnotify_backend.h>
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#include <linux/init.h>
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#include <linux/jiffies.h>
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#include <linux/kernel.h> /* UINT_MAX */
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#include <linux/mount.h>
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#include <linux/sched.h>
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#include <linux/sched/user.h>
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#include <linux/sched/signal.h>
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#include <linux/types.h>
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#include <linux/wait.h>
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#include <linux/audit.h>
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#include <linux/sched/mm.h>
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#include <linux/statfs.h>
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#include "fanotify.h"
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static bool should_merge(struct fsnotify_event *old_fsn,
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struct fsnotify_event *new_fsn)
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{
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struct fanotify_event *old, *new;
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pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
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old = FANOTIFY_E(old_fsn);
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new = FANOTIFY_E(new_fsn);
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if (old_fsn->inode != new_fsn->inode || old->pid != new->pid ||
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old->fh_type != new->fh_type || old->fh_len != new->fh_len)
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return false;
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if (fanotify_event_has_path(old)) {
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return old->path.mnt == new->path.mnt &&
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old->path.dentry == new->path.dentry;
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} else if (fanotify_event_has_fid(old)) {
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/*
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* We want to merge many dirent events in the same dir (i.e.
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* creates/unlinks/renames), but we do not want to merge dirent
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* events referring to subdirs with dirent events referring to
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* non subdirs, otherwise, user won't be able to tell from a
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* mask FAN_CREATE|FAN_DELETE|FAN_ONDIR if it describes mkdir+
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* unlink pair or rmdir+create pair of events.
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*/
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return (old->mask & FS_ISDIR) == (new->mask & FS_ISDIR) &&
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fanotify_fid_equal(&old->fid, &new->fid, old->fh_len);
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}
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/* Do not merge events if we failed to encode fid */
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return false;
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}
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/* and the list better be locked by something too! */
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static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
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{
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struct fsnotify_event *test_event;
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struct fanotify_event *new;
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pr_debug("%s: list=%p event=%p\n", __func__, list, event);
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new = FANOTIFY_E(event);
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/*
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* Don't merge a permission event with any other event so that we know
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* the event structure we have created in fanotify_handle_event() is the
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* one we should check for permission response.
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*/
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if (fanotify_is_perm_event(new->mask))
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return 0;
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list_for_each_entry_reverse(test_event, list, list) {
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if (should_merge(test_event, event)) {
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FANOTIFY_E(test_event)->mask |= new->mask;
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return 1;
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}
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}
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return 0;
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}
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/*
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* Wait for response to permission event. The function also takes care of
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* freeing the permission event (or offloads that in case the wait is canceled
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* by a signal). The function returns 0 in case access got allowed by userspace,
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* -EPERM in case userspace disallowed the access, and -ERESTARTSYS in case
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* the wait got interrupted by a signal.
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*/
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static int fanotify_get_response(struct fsnotify_group *group,
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struct fanotify_perm_event *event,
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struct fsnotify_iter_info *iter_info)
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{
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int ret;
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pr_debug("%s: group=%p event=%p\n", __func__, group, event);
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ret = wait_event_killable(group->fanotify_data.access_waitq,
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event->state == FAN_EVENT_ANSWERED);
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/* Signal pending? */
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if (ret < 0) {
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spin_lock(&group->notification_lock);
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/* Event reported to userspace and no answer yet? */
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if (event->state == FAN_EVENT_REPORTED) {
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/* Event will get freed once userspace answers to it */
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event->state = FAN_EVENT_CANCELED;
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spin_unlock(&group->notification_lock);
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return ret;
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}
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/* Event not yet reported? Just remove it. */
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if (event->state == FAN_EVENT_INIT)
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fsnotify_remove_queued_event(group, &event->fae.fse);
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/*
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* Event may be also answered in case signal delivery raced
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* with wakeup. In that case we have nothing to do besides
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* freeing the event and reporting error.
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*/
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spin_unlock(&group->notification_lock);
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goto out;
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}
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/* userspace responded, convert to something usable */
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switch (event->response & ~FAN_AUDIT) {
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case FAN_ALLOW:
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ret = 0;
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break;
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case FAN_DENY:
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default:
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ret = -EPERM;
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}
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/* Check if the response should be audited */
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if (event->response & FAN_AUDIT)
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audit_fanotify(event->response & ~FAN_AUDIT);
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pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
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group, event, ret);
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out:
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fsnotify_destroy_event(group, &event->fae.fse);
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return ret;
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}
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/*
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* This function returns a mask for an event that only contains the flags
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* that have been specifically requested by the user. Flags that may have
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* been included within the event mask, but have not been explicitly
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* requested by the user, will not be present in the returned mask.
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*/
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static u32 fanotify_group_event_mask(struct fsnotify_group *group,
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struct fsnotify_iter_info *iter_info,
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u32 event_mask, const void *data,
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int data_type)
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{
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__u32 marks_mask = 0, marks_ignored_mask = 0;
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__u32 test_mask, user_mask = FANOTIFY_OUTGOING_EVENTS;
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const struct path *path = data;
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struct fsnotify_mark *mark;
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int type;
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pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
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__func__, iter_info->report_mask, event_mask, data, data_type);
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if (!FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
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/* Do we have path to open a file descriptor? */
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if (data_type != FSNOTIFY_EVENT_PATH)
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return 0;
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/* Path type events are only relevant for files and dirs */
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if (!d_is_reg(path->dentry) && !d_can_lookup(path->dentry))
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return 0;
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}
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fsnotify_foreach_obj_type(type) {
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if (!fsnotify_iter_should_report_type(iter_info, type))
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continue;
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mark = iter_info->marks[type];
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/*
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* If the event is for a child and this mark doesn't care about
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* events on a child, don't send it!
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*/
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if (event_mask & FS_EVENT_ON_CHILD &&
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(type != FSNOTIFY_OBJ_TYPE_INODE ||
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!(mark->mask & FS_EVENT_ON_CHILD)))
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continue;
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marks_mask |= mark->mask;
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marks_ignored_mask |= mark->ignored_mask;
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}
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test_mask = event_mask & marks_mask & ~marks_ignored_mask;
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/*
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* dirent modification events (create/delete/move) do not carry the
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* child entry name/inode information. Instead, we report FAN_ONDIR
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* for mkdir/rmdir so user can differentiate them from creat/unlink.
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*
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* For backward compatibility and consistency, do not report FAN_ONDIR
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* to user in legacy fanotify mode (reporting fd) and report FAN_ONDIR
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* to user in FAN_REPORT_FID mode for all event types.
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*/
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if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
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/* Do not report FAN_ONDIR without any event */
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if (!(test_mask & ~FAN_ONDIR))
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return 0;
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} else {
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user_mask &= ~FAN_ONDIR;
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}
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if (event_mask & FS_ISDIR &&
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!(marks_mask & FS_ISDIR & ~marks_ignored_mask))
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return 0;
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return test_mask & user_mask;
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}
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static int fanotify_encode_fid(struct fanotify_event *event,
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struct inode *inode, gfp_t gfp,
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__kernel_fsid_t *fsid)
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{
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struct fanotify_fid *fid = &event->fid;
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int dwords, bytes = 0;
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int err, type;
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fid->ext_fh = NULL;
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dwords = 0;
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err = -ENOENT;
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type = exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
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if (!dwords)
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goto out_err;
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bytes = dwords << 2;
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if (bytes > FANOTIFY_INLINE_FH_LEN) {
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/* Treat failure to allocate fh as failure to allocate event */
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err = -ENOMEM;
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fid->ext_fh = kmalloc(bytes, gfp);
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if (!fid->ext_fh)
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goto out_err;
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}
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type = exportfs_encode_inode_fh(inode, fanotify_fid_fh(fid, bytes),
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&dwords, NULL);
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err = -EINVAL;
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if (!type || type == FILEID_INVALID || bytes != dwords << 2)
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goto out_err;
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fid->fsid = *fsid;
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event->fh_len = bytes;
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return type;
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out_err:
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pr_warn_ratelimited("fanotify: failed to encode fid (fsid=%x.%x, "
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"type=%d, bytes=%d, err=%i)\n",
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fsid->val[0], fsid->val[1], type, bytes, err);
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kfree(fid->ext_fh);
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fid->ext_fh = NULL;
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event->fh_len = 0;
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return FILEID_INVALID;
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}
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/*
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* The inode to use as identifier when reporting fid depends on the event.
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* Report the modified directory inode on dirent modification events.
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* Report the "victim" inode otherwise.
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* For example:
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* FS_ATTRIB reports the child inode even if reported on a watched parent.
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* FS_CREATE reports the modified dir inode and not the created inode.
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*/
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static struct inode *fanotify_fid_inode(struct inode *to_tell, u32 event_mask,
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const void *data, int data_type)
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{
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if (event_mask & ALL_FSNOTIFY_DIRENT_EVENTS)
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return to_tell;
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else if (data_type == FSNOTIFY_EVENT_INODE)
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return (struct inode *)data;
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else if (data_type == FSNOTIFY_EVENT_PATH)
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return d_inode(((struct path *)data)->dentry);
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return NULL;
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}
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struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
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struct inode *inode, u32 mask,
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const void *data, int data_type,
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__kernel_fsid_t *fsid)
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{
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struct fanotify_event *event = NULL;
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gfp_t gfp = GFP_KERNEL_ACCOUNT;
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struct inode *id = fanotify_fid_inode(inode, mask, data, data_type);
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/*
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* For queues with unlimited length lost events are not expected and
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* can possibly have security implications. Avoid losing events when
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* memory is short. For the limited size queues, avoid OOM killer in the
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* target monitoring memcg as it may have security repercussion.
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*/
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if (group->max_events == UINT_MAX)
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gfp |= __GFP_NOFAIL;
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else
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gfp |= __GFP_RETRY_MAYFAIL;
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/* Whoever is interested in the event, pays for the allocation. */
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memalloc_use_memcg(group->memcg);
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if (fanotify_is_perm_event(mask)) {
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struct fanotify_perm_event *pevent;
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pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp);
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if (!pevent)
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goto out;
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event = &pevent->fae;
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pevent->response = 0;
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pevent->state = FAN_EVENT_INIT;
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goto init;
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}
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event = kmem_cache_alloc(fanotify_event_cachep, gfp);
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if (!event)
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goto out;
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init: __maybe_unused
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fsnotify_init_event(&event->fse, inode);
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event->mask = mask;
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if (FAN_GROUP_FLAG(group, FAN_REPORT_TID))
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event->pid = get_pid(task_pid(current));
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else
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event->pid = get_pid(task_tgid(current));
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event->fh_len = 0;
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if (id && FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
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/* Report the event without a file identifier on encode error */
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event->fh_type = fanotify_encode_fid(event, id, gfp, fsid);
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} else if (data_type == FSNOTIFY_EVENT_PATH) {
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event->fh_type = FILEID_ROOT;
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event->path = *((struct path *)data);
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path_get(&event->path);
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} else {
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event->fh_type = FILEID_INVALID;
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event->path.mnt = NULL;
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event->path.dentry = NULL;
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}
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out:
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memalloc_unuse_memcg();
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return event;
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}
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/*
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* Get cached fsid of the filesystem containing the object from any connector.
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* All connectors are supposed to have the same fsid, but we do not verify that
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* here.
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*/
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static __kernel_fsid_t fanotify_get_fsid(struct fsnotify_iter_info *iter_info)
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{
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int type;
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__kernel_fsid_t fsid = {};
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fsnotify_foreach_obj_type(type) {
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struct fsnotify_mark_connector *conn;
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if (!fsnotify_iter_should_report_type(iter_info, type))
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continue;
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conn = READ_ONCE(iter_info->marks[type]->connector);
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/* Mark is just getting destroyed or created? */
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if (!conn)
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continue;
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if (!(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID))
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continue;
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/* Pairs with smp_wmb() in fsnotify_add_mark_list() */
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smp_rmb();
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fsid = conn->fsid;
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if (WARN_ON_ONCE(!fsid.val[0] && !fsid.val[1]))
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continue;
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return fsid;
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}
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return fsid;
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}
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static int fanotify_handle_event(struct fsnotify_group *group,
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struct inode *inode,
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u32 mask, const void *data, int data_type,
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const struct qstr *file_name, u32 cookie,
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struct fsnotify_iter_info *iter_info)
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{
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int ret = 0;
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struct fanotify_event *event;
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struct fsnotify_event *fsn_event;
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__kernel_fsid_t fsid = {};
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BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
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BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
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BUILD_BUG_ON(FAN_ATTRIB != FS_ATTRIB);
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BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
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BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
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BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
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BUILD_BUG_ON(FAN_MOVED_TO != FS_MOVED_TO);
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BUILD_BUG_ON(FAN_MOVED_FROM != FS_MOVED_FROM);
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BUILD_BUG_ON(FAN_CREATE != FS_CREATE);
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BUILD_BUG_ON(FAN_DELETE != FS_DELETE);
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BUILD_BUG_ON(FAN_DELETE_SELF != FS_DELETE_SELF);
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BUILD_BUG_ON(FAN_MOVE_SELF != FS_MOVE_SELF);
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BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
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BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
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BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
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BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
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BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
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BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
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BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
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BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 19);
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mask = fanotify_group_event_mask(group, iter_info, mask, data,
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data_type);
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if (!mask)
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return 0;
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pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
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mask);
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if (fanotify_is_perm_event(mask)) {
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/*
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* fsnotify_prepare_user_wait() fails if we race with mark
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* deletion. Just let the operation pass in that case.
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*/
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if (!fsnotify_prepare_user_wait(iter_info))
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return 0;
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}
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if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
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fsid = fanotify_get_fsid(iter_info);
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/* Racing with mark destruction or creation? */
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if (!fsid.val[0] && !fsid.val[1])
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return 0;
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}
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event = fanotify_alloc_event(group, inode, mask, data, data_type,
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&fsid);
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ret = -ENOMEM;
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if (unlikely(!event)) {
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/*
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* We don't queue overflow events for permission events as
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* there the access is denied and so no event is in fact lost.
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*/
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if (!fanotify_is_perm_event(mask))
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fsnotify_queue_overflow(group);
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goto finish;
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}
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fsn_event = &event->fse;
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ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
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if (ret) {
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/* Permission events shouldn't be merged */
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BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
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/* Our event wasn't used in the end. Free it. */
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fsnotify_destroy_event(group, fsn_event);
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ret = 0;
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} else if (fanotify_is_perm_event(mask)) {
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ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event),
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iter_info);
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}
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finish:
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if (fanotify_is_perm_event(mask))
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fsnotify_finish_user_wait(iter_info);
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return ret;
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}
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static void fanotify_free_group_priv(struct fsnotify_group *group)
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{
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struct user_struct *user;
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user = group->fanotify_data.user;
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atomic_dec(&user->fanotify_listeners);
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free_uid(user);
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}
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static void fanotify_free_event(struct fsnotify_event *fsn_event)
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{
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struct fanotify_event *event;
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event = FANOTIFY_E(fsn_event);
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if (fanotify_event_has_path(event))
|
|
path_put(&event->path);
|
|
else if (fanotify_event_has_ext_fh(event))
|
|
kfree(event->fid.ext_fh);
|
|
put_pid(event->pid);
|
|
if (fanotify_is_perm_event(event->mask)) {
|
|
kmem_cache_free(fanotify_perm_event_cachep,
|
|
FANOTIFY_PE(fsn_event));
|
|
return;
|
|
}
|
|
kmem_cache_free(fanotify_event_cachep, event);
|
|
}
|
|
|
|
static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
|
|
{
|
|
kmem_cache_free(fanotify_mark_cache, fsn_mark);
|
|
}
|
|
|
|
const struct fsnotify_ops fanotify_fsnotify_ops = {
|
|
.handle_event = fanotify_handle_event,
|
|
.free_group_priv = fanotify_free_group_priv,
|
|
.free_event = fanotify_free_event,
|
|
.free_mark = fanotify_free_mark,
|
|
};
|