| // SPDX-License-Identifier: GPL-2.0 |
| #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/sched/user.h> |
| #include <linux/sched/signal.h> |
| #include <linux/types.h> |
| #include <linux/wait.h> |
| #include <linux/audit.h> |
| #include <linux/sched/mm.h> |
| |
| #include "fanotify.h" |
| |
| static bool should_merge(struct fsnotify_event *old_fsn, |
| struct fsnotify_event *new_fsn) |
| { |
| struct fanotify_event_info *old, *new; |
| |
| pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn); |
| old = FANOTIFY_E(old_fsn); |
| new = FANOTIFY_E(new_fsn); |
| |
| if (old_fsn->inode == new_fsn->inode && old->pid == new->pid && |
| old->path.mnt == new->path.mnt && |
| old->path.dentry == new->path.dentry) |
| return true; |
| return false; |
| } |
| |
| /* and the list better be locked by something too! */ |
| static int fanotify_merge(struct list_head *list, struct fsnotify_event *event) |
| { |
| struct fsnotify_event *test_event; |
| |
| pr_debug("%s: list=%p event=%p\n", __func__, list, event); |
| |
| /* |
| * Don't merge a permission event with any other event so that we know |
| * the event structure we have created in fanotify_handle_event() is the |
| * one we should check for permission response. |
| */ |
| if (fanotify_is_perm_event(event->mask)) |
| return 0; |
| |
| list_for_each_entry_reverse(test_event, list, list) { |
| if (should_merge(test_event, event)) { |
| test_event->mask |= event->mask; |
| return 1; |
| } |
| } |
| |
| return 0; |
| } |
| |
| static int fanotify_get_response(struct fsnotify_group *group, |
| struct fanotify_perm_event_info *event, |
| struct fsnotify_iter_info *iter_info) |
| { |
| 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 */ |
| switch (event->response & ~FAN_AUDIT) { |
| case FAN_ALLOW: |
| ret = 0; |
| break; |
| case FAN_DENY: |
| default: |
| ret = -EPERM; |
| } |
| |
| /* Check if the response should be audited */ |
| if (event->response & FAN_AUDIT) |
| audit_fanotify(event->response & ~FAN_AUDIT); |
| |
| event->response = 0; |
| |
| pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__, |
| group, event, ret); |
| |
| return ret; |
| } |
| |
| /* |
| * This function returns a mask for an event that only contains the flags |
| * that have been specifically requested by the user. Flags that may have |
| * been included within the event mask, but have not been explicitly |
| * requested by the user, will not be present in the returned mask. |
| */ |
| static u32 fanotify_group_event_mask(struct fsnotify_iter_info *iter_info, |
| u32 event_mask, const void *data, |
| int data_type) |
| { |
| __u32 marks_mask = 0, marks_ignored_mask = 0; |
| const struct path *path = data; |
| struct fsnotify_mark *mark; |
| int type; |
| |
| pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n", |
| __func__, iter_info->report_mask, event_mask, data, data_type); |
| |
| /* If we don't have enough info to send an event to userspace say no */ |
| if (data_type != FSNOTIFY_EVENT_PATH) |
| return 0; |
| |
| /* Sorry, fanotify only gives a damn about files and dirs */ |
| if (!d_is_reg(path->dentry) && |
| !d_can_lookup(path->dentry)) |
| return 0; |
| |
| fsnotify_foreach_obj_type(type) { |
| if (!fsnotify_iter_should_report_type(iter_info, type)) |
| continue; |
| mark = iter_info->marks[type]; |
| /* |
| * If the event is for a child and this mark doesn't care about |
| * events on a child, don't send it! |
| */ |
| if (event_mask & FS_EVENT_ON_CHILD && |
| (type != FSNOTIFY_OBJ_TYPE_INODE || |
| !(mark->mask & FS_EVENT_ON_CHILD))) |
| continue; |
| |
| marks_mask |= mark->mask; |
| marks_ignored_mask |= mark->ignored_mask; |
| } |
| |
| if (d_is_dir(path->dentry) && |
| !(marks_mask & FS_ISDIR & ~marks_ignored_mask)) |
| return 0; |
| |
| return event_mask & FANOTIFY_OUTGOING_EVENTS & marks_mask & |
| ~marks_ignored_mask; |
| } |
| |
| struct fanotify_event_info *fanotify_alloc_event(struct fsnotify_group *group, |
| struct inode *inode, u32 mask, |
| const struct path *path) |
| { |
| struct fanotify_event_info *event = NULL; |
| gfp_t gfp = GFP_KERNEL_ACCOUNT; |
| |
| /* |
| * For queues with unlimited length lost events are not expected and |
| * can possibly have security implications. Avoid losing events when |
| * memory is short. |
| */ |
| if (group->max_events == UINT_MAX) |
| gfp |= __GFP_NOFAIL; |
| |
| /* Whoever is interested in the event, pays for the allocation. */ |
| memalloc_use_memcg(group->memcg); |
| |
| if (fanotify_is_perm_event(mask)) { |
| struct fanotify_perm_event_info *pevent; |
| |
| pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp); |
| if (!pevent) |
| goto out; |
| event = &pevent->fae; |
| pevent->response = 0; |
| goto init; |
| } |
| event = kmem_cache_alloc(fanotify_event_cachep, gfp); |
| if (!event) |
| goto out; |
| init: __maybe_unused |
| fsnotify_init_event(&event->fse, inode, mask); |
| if (FAN_GROUP_FLAG(group, FAN_REPORT_TID)) |
| event->pid = get_pid(task_pid(current)); |
| else |
| event->pid = get_pid(task_tgid(current)); |
| if (path) { |
| event->path = *path; |
| path_get(&event->path); |
| } else { |
| event->path.mnt = NULL; |
| event->path.dentry = NULL; |
| } |
| out: |
| memalloc_unuse_memcg(); |
| return event; |
| } |
| |
| static int fanotify_handle_event(struct fsnotify_group *group, |
| struct inode *inode, |
| u32 mask, const void *data, int data_type, |
| const unsigned char *file_name, u32 cookie, |
| struct fsnotify_iter_info *iter_info) |
| { |
| int ret = 0; |
| struct fanotify_event_info *event; |
| struct fsnotify_event *fsn_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); |
| BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM); |
| BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM); |
| BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR); |
| BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC); |
| BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM); |
| |
| BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 12); |
| |
| mask = fanotify_group_event_mask(iter_info, mask, data, data_type); |
| if (!mask) |
| return 0; |
| |
| pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode, |
| mask); |
| |
| if (fanotify_is_perm_event(mask)) { |
| /* |
| * fsnotify_prepare_user_wait() fails if we race with mark |
| * deletion. Just let the operation pass in that case. |
| */ |
| if (!fsnotify_prepare_user_wait(iter_info)) |
| return 0; |
| } |
| |
| event = fanotify_alloc_event(group, inode, mask, data); |
| ret = -ENOMEM; |
| if (unlikely(!event)) { |
| /* |
| * We don't queue overflow events for permission events as |
| * there the access is denied and so no event is in fact lost. |
| */ |
| if (!fanotify_is_perm_event(mask)) |
| fsnotify_queue_overflow(group); |
| goto finish; |
| } |
| |
| fsn_event = &event->fse; |
| ret = fsnotify_add_event(group, fsn_event, fanotify_merge); |
| if (ret) { |
| /* Permission events shouldn't be merged */ |
| BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS); |
| /* Our event wasn't used in the end. Free it. */ |
| fsnotify_destroy_event(group, fsn_event); |
| |
| ret = 0; |
| } else if (fanotify_is_perm_event(mask)) { |
| ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event), |
| iter_info); |
| fsnotify_destroy_event(group, fsn_event); |
| } |
| finish: |
| if (fanotify_is_perm_event(mask)) |
| fsnotify_finish_user_wait(iter_info); |
| |
| return ret; |
| } |
| |
| static void fanotify_free_group_priv(struct fsnotify_group *group) |
| { |
| struct user_struct *user; |
| |
| user = group->fanotify_data.user; |
| atomic_dec(&user->fanotify_listeners); |
| free_uid(user); |
| } |
| |
| static void fanotify_free_event(struct fsnotify_event *fsn_event) |
| { |
| struct fanotify_event_info *event; |
| |
| event = FANOTIFY_E(fsn_event); |
| path_put(&event->path); |
| put_pid(event->pid); |
| if (fanotify_is_perm_event(fsn_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, |
| }; |