diff options
Diffstat (limited to 'fs/notify/fanotify/fanotify_user.c')
| -rw-r--r-- | fs/notify/fanotify/fanotify_user.c | 1349 |
1 files changed, 1349 insertions, 0 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c new file mode 100644 index 000000000..84de9f97b --- /dev/null +++ b/fs/notify/fanotify/fanotify_user.c @@ -0,0 +1,1349 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/fanotify.h> +#include <linux/fcntl.h> +#include <linux/file.h> +#include <linux/fs.h> +#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/slab.h> +#include <linux/types.h> +#include <linux/uaccess.h> +#include <linux/compat.h> +#include <linux/sched/signal.h> +#include <linux/memcontrol.h> +#include <linux/statfs.h> +#include <linux/exportfs.h> + +#include <asm/ioctls.h> + +#include "../../mount.h" +#include "../fdinfo.h" +#include "fanotify.h" + +#define FANOTIFY_DEFAULT_MAX_EVENTS 16384 +#define FANOTIFY_DEFAULT_MAX_MARKS 8192 +#define FANOTIFY_DEFAULT_MAX_LISTENERS 128 + +/* + * All flags that may be specified in parameter event_f_flags of fanotify_init. + * + * Internal and external open flags are stored together in field f_flags of + * struct file. Only external open flags shall be allowed in event_f_flags. + * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be + * excluded. + */ +#define FANOTIFY_INIT_ALL_EVENT_F_BITS ( \ + O_ACCMODE | O_APPEND | O_NONBLOCK | \ + __O_SYNC | O_DSYNC | O_CLOEXEC | \ + O_LARGEFILE | O_NOATIME ) + +extern const struct fsnotify_ops fanotify_fsnotify_ops; + +struct kmem_cache *fanotify_mark_cache __read_mostly; +struct kmem_cache *fanotify_fid_event_cachep __read_mostly; +struct kmem_cache *fanotify_path_event_cachep __read_mostly; +struct kmem_cache *fanotify_perm_event_cachep __read_mostly; + +#define FANOTIFY_EVENT_ALIGN 4 +#define FANOTIFY_INFO_HDR_LEN \ + (sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle)) + +static int fanotify_fid_info_len(int fh_len, int name_len) +{ + int info_len = fh_len; + + if (name_len) + info_len += name_len + 1; + + return roundup(FANOTIFY_INFO_HDR_LEN + info_len, FANOTIFY_EVENT_ALIGN); +} + +static int fanotify_event_info_len(unsigned int fid_mode, + struct fanotify_event *event) +{ + struct fanotify_info *info = fanotify_event_info(event); + int dir_fh_len = fanotify_event_dir_fh_len(event); + int fh_len = fanotify_event_object_fh_len(event); + int info_len = 0; + int dot_len = 0; + + if (dir_fh_len) { + info_len += fanotify_fid_info_len(dir_fh_len, info->name_len); + } else if ((fid_mode & FAN_REPORT_NAME) && (event->mask & FAN_ONDIR)) { + /* + * With group flag FAN_REPORT_NAME, if name was not recorded in + * event on a directory, we will report the name ".". + */ + dot_len = 1; + } + + if (fh_len) + info_len += fanotify_fid_info_len(fh_len, dot_len); + + return info_len; +} + +/* + * Get an fanotify notification event if one exists and is small + * enough to fit in "count". Return an error pointer if the count + * is not large enough. When permission event is dequeued, its state is + * updated accordingly. + */ +static struct fanotify_event *get_one_event(struct fsnotify_group *group, + size_t count) +{ + size_t event_size = FAN_EVENT_METADATA_LEN; + struct fanotify_event *event = NULL; + unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS); + + pr_debug("%s: group=%p count=%zd\n", __func__, group, count); + + spin_lock(&group->notification_lock); + if (fsnotify_notify_queue_is_empty(group)) + goto out; + + if (fid_mode) { + event_size += fanotify_event_info_len(fid_mode, + FANOTIFY_E(fsnotify_peek_first_event(group))); + } + + if (event_size > count) { + event = ERR_PTR(-EINVAL); + goto out; + } + event = FANOTIFY_E(fsnotify_remove_first_event(group)); + if (fanotify_is_perm_event(event->mask)) + FANOTIFY_PERM(event)->state = FAN_EVENT_REPORTED; +out: + spin_unlock(&group->notification_lock); + return event; +} + +static int create_fd(struct fsnotify_group *group, struct path *path, + struct file **file) +{ + int client_fd; + struct file *new_file; + + client_fd = get_unused_fd_flags(group->fanotify_data.f_flags); + if (client_fd < 0) + return client_fd; + + /* + * we need a new file handle for the userspace program so it can read even if it was + * originally opened O_WRONLY. + */ + new_file = dentry_open(path, + group->fanotify_data.f_flags | FMODE_NONOTIFY, + current_cred()); + 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 { + *file = new_file; + } + + return client_fd; +} + +/* + * Finish processing of permission event by setting it to ANSWERED state and + * drop group->notification_lock. + */ +static void finish_permission_event(struct fsnotify_group *group, + struct fanotify_perm_event *event, + unsigned int response) + __releases(&group->notification_lock) +{ + bool destroy = false; + + assert_spin_locked(&group->notification_lock); + event->response = response; + if (event->state == FAN_EVENT_CANCELED) + destroy = true; + else + event->state = FAN_EVENT_ANSWERED; + spin_unlock(&group->notification_lock); + if (destroy) + fsnotify_destroy_event(group, &event->fae.fse); +} + +static int process_access_response(struct fsnotify_group *group, + struct fanotify_response *response_struct) +{ + struct fanotify_perm_event *event; + int fd = response_struct->fd; + int response = response_struct->response; + + pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group, + fd, response); + /* + * make sure the response is valid, if invalid we do nothing and either + * userspace can send a valid response or we will clean it up after the + * timeout + */ + switch (response & ~FAN_AUDIT) { + case FAN_ALLOW: + case FAN_DENY: + break; + default: + return -EINVAL; + } + + if (fd < 0) + return -EINVAL; + + if ((response & FAN_AUDIT) && !FAN_GROUP_FLAG(group, FAN_ENABLE_AUDIT)) + return -EINVAL; + + spin_lock(&group->notification_lock); + list_for_each_entry(event, &group->fanotify_data.access_list, + fae.fse.list) { + if (event->fd != fd) + continue; + + list_del_init(&event->fae.fse.list); + finish_permission_event(group, event, response); + wake_up(&group->fanotify_data.access_waitq); + return 0; + } + spin_unlock(&group->notification_lock); + + return -ENOENT; +} + +static int copy_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh, + int info_type, const char *name, size_t name_len, + char __user *buf, size_t count) +{ + struct fanotify_event_info_fid info = { }; + struct file_handle handle = { }; + unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *fh_buf; + size_t fh_len = fh ? fh->len : 0; + size_t info_len = fanotify_fid_info_len(fh_len, name_len); + size_t len = info_len; + + pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n", + __func__, fh_len, name_len, info_len, count); + + if (!fh_len) + return 0; + + if (WARN_ON_ONCE(len < sizeof(info) || len > count)) + return -EFAULT; + + /* + * Copy event info fid header followed by variable sized file handle + * and optionally followed by variable sized filename. + */ + switch (info_type) { + case FAN_EVENT_INFO_TYPE_FID: + case FAN_EVENT_INFO_TYPE_DFID: + if (WARN_ON_ONCE(name_len)) + return -EFAULT; + break; + case FAN_EVENT_INFO_TYPE_DFID_NAME: + if (WARN_ON_ONCE(!name || !name_len)) + return -EFAULT; + break; + default: + return -EFAULT; + } + + info.hdr.info_type = info_type; + info.hdr.len = len; + info.fsid = *fsid; + if (copy_to_user(buf, &info, sizeof(info))) + return -EFAULT; + + buf += sizeof(info); + len -= sizeof(info); + if (WARN_ON_ONCE(len < sizeof(handle))) + return -EFAULT; + + handle.handle_type = fh->type; + handle.handle_bytes = fh_len; + if (copy_to_user(buf, &handle, sizeof(handle))) + return -EFAULT; + + buf += sizeof(handle); + len -= sizeof(handle); + if (WARN_ON_ONCE(len < fh_len)) + return -EFAULT; + + /* + * For an inline fh and inline file name, copy through stack to exclude + * the copy from usercopy hardening protections. + */ + fh_buf = fanotify_fh_buf(fh); + if (fh_len <= FANOTIFY_INLINE_FH_LEN) { + memcpy(bounce, fh_buf, fh_len); + fh_buf = bounce; + } + if (copy_to_user(buf, fh_buf, fh_len)) + return -EFAULT; + + buf += fh_len; + len -= fh_len; + + if (name_len) { + /* Copy the filename with terminating null */ + name_len++; + if (WARN_ON_ONCE(len < name_len)) + return -EFAULT; + + if (copy_to_user(buf, name, name_len)) + return -EFAULT; + + buf += name_len; + len -= name_len; + } + + /* Pad with 0's */ + WARN_ON_ONCE(len < 0 || len >= FANOTIFY_EVENT_ALIGN); + if (len > 0 && clear_user(buf, len)) + return -EFAULT; + + return info_len; +} + +static ssize_t copy_event_to_user(struct fsnotify_group *group, + struct fanotify_event *event, + char __user *buf, size_t count) +{ + struct fanotify_event_metadata metadata; + struct path *path = fanotify_event_path(event); + struct fanotify_info *info = fanotify_event_info(event); + unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS); + struct file *f = NULL; + int ret, fd = FAN_NOFD; + int info_type = 0; + + pr_debug("%s: group=%p event=%p\n", __func__, group, event); + + metadata.event_len = FAN_EVENT_METADATA_LEN + + fanotify_event_info_len(fid_mode, event); + metadata.metadata_len = FAN_EVENT_METADATA_LEN; + metadata.vers = FANOTIFY_METADATA_VERSION; + metadata.reserved = 0; + metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS; + metadata.pid = pid_vnr(event->pid); + + if (path && path->mnt && path->dentry) { + fd = create_fd(group, path, &f); + if (fd < 0) + return fd; + } + metadata.fd = fd; + + ret = -EFAULT; + /* + * Sanity check copy size in case get_one_event() and + * event_len sizes ever get out of sync. + */ + if (WARN_ON_ONCE(metadata.event_len > count)) + goto out_close_fd; + + if (copy_to_user(buf, &metadata, FAN_EVENT_METADATA_LEN)) + goto out_close_fd; + + buf += FAN_EVENT_METADATA_LEN; + count -= FAN_EVENT_METADATA_LEN; + + if (fanotify_is_perm_event(event->mask)) + FANOTIFY_PERM(event)->fd = fd; + + /* Event info records order is: dir fid + name, child fid */ + if (fanotify_event_dir_fh_len(event)) { + info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME : + FAN_EVENT_INFO_TYPE_DFID; + ret = copy_info_to_user(fanotify_event_fsid(event), + fanotify_info_dir_fh(info), + info_type, fanotify_info_name(info), + info->name_len, buf, count); + if (ret < 0) + goto out_close_fd; + + buf += ret; + count -= ret; + } + + if (fanotify_event_object_fh_len(event)) { + const char *dot = NULL; + int dot_len = 0; + + if (fid_mode == FAN_REPORT_FID || info_type) { + /* + * With only group flag FAN_REPORT_FID only type FID is + * reported. Second info record type is always FID. + */ + info_type = FAN_EVENT_INFO_TYPE_FID; + } else if ((fid_mode & FAN_REPORT_NAME) && + (event->mask & FAN_ONDIR)) { + /* + * With group flag FAN_REPORT_NAME, if name was not + * recorded in an event on a directory, report the + * name "." with info type DFID_NAME. + */ + info_type = FAN_EVENT_INFO_TYPE_DFID_NAME; + dot = "."; + dot_len = 1; + } else if ((event->mask & ALL_FSNOTIFY_DIRENT_EVENTS) || + (event->mask & FAN_ONDIR)) { + /* + * With group flag FAN_REPORT_DIR_FID, a single info + * record has type DFID for directory entry modification + * event and for event on a directory. + */ + info_type = FAN_EVENT_INFO_TYPE_DFID; + } else { + /* + * With group flags FAN_REPORT_DIR_FID|FAN_REPORT_FID, + * a single info record has type FID for event on a + * non-directory, when there is no directory to report. + * For example, on FAN_DELETE_SELF event. + */ + info_type = FAN_EVENT_INFO_TYPE_FID; + } + + ret = copy_info_to_user(fanotify_event_fsid(event), + fanotify_event_object_fh(event), + info_type, dot, dot_len, buf, count); + if (ret < 0) + goto out_close_fd; + + buf += ret; + count -= ret; + } + + if (f) + fd_install(fd, f); + + return metadata.event_len; + +out_close_fd: + if (fd != FAN_NOFD) { + put_unused_fd(fd); + fput(f); + } + return ret; +} + +/* intofiy userspace file descriptor functions */ +static __poll_t fanotify_poll(struct file *file, poll_table *wait) +{ + struct fsnotify_group *group = file->private_data; + __poll_t ret = 0; + + poll_wait(file, &group->notification_waitq, wait); + spin_lock(&group->notification_lock); + if (!fsnotify_notify_queue_is_empty(group)) + ret = EPOLLIN | EPOLLRDNORM; + spin_unlock(&group->notification_lock); + + return ret; +} + +static ssize_t fanotify_read(struct file *file, char __user *buf, + size_t count, loff_t *pos) +{ + struct fsnotify_group *group; + struct fanotify_event *event; + char __user *start; + int ret; + DEFINE_WAIT_FUNC(wait, woken_wake_function); + + start = buf; + group = file->private_data; + + pr_debug("%s: group=%p\n", __func__, group); + + add_wait_queue(&group->notification_waitq, &wait); + while (1) { + /* + * User can supply arbitrarily large buffer. Avoid softlockups + * in case there are lots of available events. + */ + cond_resched(); + event = get_one_event(group, count); + if (IS_ERR(event)) { + ret = PTR_ERR(event); + break; + } + + if (!event) { + ret = -EAGAIN; + if (file->f_flags & O_NONBLOCK) + break; + + ret = -ERESTARTSYS; + if (signal_pending(current)) + break; + + if (start != buf) + break; + + wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT); + continue; + } + + ret = copy_event_to_user(group, event, buf, count); + if (unlikely(ret == -EOPENSTALE)) { + /* + * We cannot report events with stale fd so drop it. + * Setting ret to 0 will continue the event loop and + * do the right thing if there are no more events to + * read (i.e. return bytes read, -EAGAIN or wait). + */ + ret = 0; + } + + /* + * Permission events get queued to wait for response. Other + * events can be destroyed now. + */ + if (!fanotify_is_perm_event(event->mask)) { + fsnotify_destroy_event(group, &event->fse); + } else { + if (ret <= 0) { + spin_lock(&group->notification_lock); + finish_permission_event(group, + FANOTIFY_PERM(event), FAN_DENY); + wake_up(&group->fanotify_data.access_waitq); + } else { + spin_lock(&group->notification_lock); + list_add_tail(&event->fse.list, + &group->fanotify_data.access_list); + spin_unlock(&group->notification_lock); + } + } + if (ret < 0) + break; + buf += ret; + count -= ret; + } + remove_wait_queue(&group->notification_waitq, &wait); + + if (start != buf && ret != -EFAULT) + ret = buf - start; + return ret; +} + +static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos) +{ + struct fanotify_response response = { .fd = -1, .response = -1 }; + struct fsnotify_group *group; + int ret; + + if (!IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) + return -EINVAL; + + group = file->private_data; + + if (count < sizeof(response)) + return -EINVAL; + + count = sizeof(response); + + pr_debug("%s: group=%p count=%zu\n", __func__, group, count); + + if (copy_from_user(&response, buf, count)) + return -EFAULT; + + ret = process_access_response(group, &response); + if (ret < 0) + count = ret; + + return count; +} + +static int fanotify_release(struct inode *ignored, struct file *file) +{ + struct fsnotify_group *group = file->private_data; + + /* + * Stop new events from arriving in the notification queue. since + * userspace cannot use fanotify fd anymore, no event can enter or + * leave access_list by now either. + */ + fsnotify_group_stop_queueing(group); + + /* + * Process all permission events on access_list and notification queue + * and simulate reply from userspace. + */ + spin_lock(&group->notification_lock); + while (!list_empty(&group->fanotify_data.access_list)) { + struct fanotify_perm_event *event; + + event = list_first_entry(&group->fanotify_data.access_list, + struct fanotify_perm_event, fae.fse.list); + list_del_init(&event->fae.fse.list); + finish_permission_event(group, event, FAN_ALLOW); + spin_lock(&group->notification_lock); + } + + /* + * Destroy all non-permission events. For permission events just + * dequeue them and set the response. They will be freed once the + * response is consumed and fanotify_get_response() returns. + */ + while (!fsnotify_notify_queue_is_empty(group)) { + struct fanotify_event *event; + + event = FANOTIFY_E(fsnotify_remove_first_event(group)); + if (!(event->mask & FANOTIFY_PERM_EVENTS)) { + spin_unlock(&group->notification_lock); + fsnotify_destroy_event(group, &event->fse); + } else { + finish_permission_event(group, FANOTIFY_PERM(event), + FAN_ALLOW); + } + spin_lock(&group->notification_lock); + } + spin_unlock(&group->notification_lock); + + /* Response for all permission events it set, wakeup waiters */ + wake_up(&group->fanotify_data.access_waitq); + + /* matches the fanotify_init->fsnotify_alloc_group */ + fsnotify_destroy_group(group); + + return 0; +} + +static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg) +{ + struct fsnotify_group *group; + struct fsnotify_event *fsn_event; + void __user *p; + int ret = -ENOTTY; + size_t send_len = 0; + + group = file->private_data; + + p = (void __user *) arg; + + switch (cmd) { + case FIONREAD: + spin_lock(&group->notification_lock); + list_for_each_entry(fsn_event, &group->notification_list, list) + send_len += FAN_EVENT_METADATA_LEN; + spin_unlock(&group->notification_lock); + ret = put_user(send_len, (int __user *) p); + break; + } + + return ret; +} + +static const struct file_operations fanotify_fops = { + .show_fdinfo = fanotify_show_fdinfo, + .poll = fanotify_poll, + .read = fanotify_read, + .write = fanotify_write, + .fasync = NULL, + .release = fanotify_release, + .unlocked_ioctl = fanotify_ioctl, + .compat_ioctl = compat_ptr_ioctl, + .llseek = noop_llseek, +}; + +static int fanotify_find_path(int dfd, const char __user *filename, + struct path *path, unsigned int flags, __u64 mask, + unsigned int obj_type) +{ + int ret; + + pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__, + dfd, filename, flags); + + if (filename == NULL) { + struct fd f = fdget(dfd); + + ret = -EBADF; + if (!f.file) + goto out; + + ret = -ENOTDIR; + if ((flags & FAN_MARK_ONLYDIR) && + !(S_ISDIR(file_inode(f.file)->i_mode))) { + fdput(f); + goto out; + } + + *path = f.file->f_path; + path_get(path); + fdput(f); + } else { + unsigned int lookup_flags = 0; + + if (!(flags & FAN_MARK_DONT_FOLLOW)) + lookup_flags |= LOOKUP_FOLLOW; + if (flags & FAN_MARK_ONLYDIR) + lookup_flags |= LOOKUP_DIRECTORY; + + ret = user_path_at(dfd, filename, lookup_flags, path); + if (ret) + goto out; + } + + /* you can only watch an inode if you have read permissions on it */ + ret = inode_permission(path->dentry->d_inode, MAY_READ); + if (ret) { + path_put(path); + goto out; + } + + ret = security_path_notify(path, mask, obj_type); + if (ret) + path_put(path); + +out: + return ret; +} + +static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark, + __u32 mask, unsigned int flags, + __u32 umask, int *destroy) +{ + __u32 oldmask = 0; + + /* umask bits cannot be removed by user */ + mask &= ~umask; + spin_lock(&fsn_mark->lock); + if (!(flags & FAN_MARK_IGNORED_MASK)) { + oldmask = fsn_mark->mask; + fsn_mark->mask &= ~mask; + } else { + fsn_mark->ignored_mask &= ~mask; + } + /* + * We need to keep the mark around even if remaining mask cannot + * result in any events (e.g. mask == FAN_ONDIR) to support incremenal + * changes to the mask. + * Destroy mark when only umask bits remain. + */ + *destroy = !((fsn_mark->mask | fsn_mark->ignored_mask) & ~umask); + spin_unlock(&fsn_mark->lock); + + return mask & oldmask; +} + +static int fanotify_remove_mark(struct fsnotify_group *group, + fsnotify_connp_t *connp, __u32 mask, + unsigned int flags, __u32 umask) +{ + struct fsnotify_mark *fsn_mark = NULL; + __u32 removed; + int destroy_mark; + + mutex_lock(&group->mark_mutex); + fsn_mark = fsnotify_find_mark(connp, group); + if (!fsn_mark) { + mutex_unlock(&group->mark_mutex); + return -ENOENT; + } + + removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags, + umask, &destroy_mark); + if (removed & fsnotify_conn_mask(fsn_mark->connector)) + fsnotify_recalc_mask(fsn_mark->connector); + if (destroy_mark) + fsnotify_detach_mark(fsn_mark); + mutex_unlock(&group->mark_mutex); + if (destroy_mark) + fsnotify_free_mark(fsn_mark); + + /* matches the fsnotify_find_mark() */ + fsnotify_put_mark(fsn_mark); + return 0; +} + +static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group, + struct vfsmount *mnt, __u32 mask, + unsigned int flags, __u32 umask) +{ + return fanotify_remove_mark(group, &real_mount(mnt)->mnt_fsnotify_marks, + mask, flags, umask); +} + +static int fanotify_remove_sb_mark(struct fsnotify_group *group, + struct super_block *sb, __u32 mask, + unsigned int flags, __u32 umask) +{ + return fanotify_remove_mark(group, &sb->s_fsnotify_marks, mask, + flags, umask); +} + +static int fanotify_remove_inode_mark(struct fsnotify_group *group, + struct inode *inode, __u32 mask, + unsigned int flags, __u32 umask) +{ + return fanotify_remove_mark(group, &inode->i_fsnotify_marks, mask, + flags, umask); +} + +static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark, + __u32 mask, + unsigned int flags) +{ + __u32 oldmask = -1; + + spin_lock(&fsn_mark->lock); + if (!(flags & FAN_MARK_IGNORED_MASK)) { + oldmask = fsn_mark->mask; + fsn_mark->mask |= mask; + } else { + fsn_mark->ignored_mask |= mask; + if (flags & FAN_MARK_IGNORED_SURV_MODIFY) + fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY; + } + spin_unlock(&fsn_mark->lock); + + return mask & ~oldmask; +} + +static struct fsnotify_mark *fanotify_add_new_mark(struct fsnotify_group *group, + fsnotify_connp_t *connp, + unsigned int type, + __kernel_fsid_t *fsid) +{ + struct fsnotify_mark *mark; + int ret; + + if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks) + return ERR_PTR(-ENOSPC); + + mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL); + if (!mark) + return ERR_PTR(-ENOMEM); + + fsnotify_init_mark(mark, group); + ret = fsnotify_add_mark_locked(mark, connp, type, 0, fsid); + if (ret) { + fsnotify_put_mark(mark); + return ERR_PTR(ret); + } + + return mark; +} + + +static int fanotify_add_mark(struct fsnotify_group *group, + fsnotify_connp_t *connp, unsigned int type, + __u32 mask, unsigned int flags, + __kernel_fsid_t *fsid) +{ + struct fsnotify_mark *fsn_mark; + __u32 added; + + mutex_lock(&group->mark_mutex); + fsn_mark = fsnotify_find_mark(connp, group); + if (!fsn_mark) { + fsn_mark = fanotify_add_new_mark(group, connp, type, fsid); + if (IS_ERR(fsn_mark)) { + mutex_unlock(&group->mark_mutex); + return PTR_ERR(fsn_mark); + } + } + added = fanotify_mark_add_to_mask(fsn_mark, mask, flags); + if (added & ~fsnotify_conn_mask(fsn_mark->connector)) + fsnotify_recalc_mask(fsn_mark->connector); + mutex_unlock(&group->mark_mutex); + + fsnotify_put_mark(fsn_mark); + return 0; +} + +static int fanotify_add_vfsmount_mark(struct fsnotify_group *group, + struct vfsmount *mnt, __u32 mask, + unsigned int flags, __kernel_fsid_t *fsid) +{ + return fanotify_add_mark(group, &real_mount(mnt)->mnt_fsnotify_marks, + FSNOTIFY_OBJ_TYPE_VFSMOUNT, mask, flags, fsid); +} + +static int fanotify_add_sb_mark(struct fsnotify_group *group, + struct super_block *sb, __u32 mask, + unsigned int flags, __kernel_fsid_t *fsid) +{ + return fanotify_add_mark(group, &sb->s_fsnotify_marks, + FSNOTIFY_OBJ_TYPE_SB, mask, flags, fsid); +} + +static int fanotify_add_inode_mark(struct fsnotify_group *group, + struct inode *inode, __u32 mask, + unsigned int flags, __kernel_fsid_t *fsid) +{ + pr_debug("%s: group=%p inode=%p\n", __func__, group, inode); + + /* + * If some other task has this inode open for write we should not add + * an ignored mark, unless that ignored mark is supposed to survive + * modification changes anyway. + */ + if ((flags & FAN_MARK_IGNORED_MASK) && + !(flags & FAN_MARK_IGNORED_SURV_MODIFY) && + inode_is_open_for_write(inode)) + return 0; + + return fanotify_add_mark(group, &inode->i_fsnotify_marks, + FSNOTIFY_OBJ_TYPE_INODE, mask, flags, fsid); +} + +static struct fsnotify_event *fanotify_alloc_overflow_event(void) +{ + struct fanotify_event *oevent; + + oevent = kmalloc(sizeof(*oevent), GFP_KERNEL_ACCOUNT); + if (!oevent) + return NULL; + + fanotify_init_event(oevent, 0, FS_Q_OVERFLOW); + oevent->type = FANOTIFY_EVENT_TYPE_OVERFLOW; + + return &oevent->fse; +} + +/* fanotify syscalls */ +SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) +{ + struct fsnotify_group *group; + int f_flags, fd; + struct user_struct *user; + unsigned int fid_mode = flags & FANOTIFY_FID_BITS; + unsigned int class = flags & FANOTIFY_CLASS_BITS; + + pr_debug("%s: flags=%x event_f_flags=%x\n", + __func__, flags, event_f_flags); + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + +#ifdef CONFIG_AUDITSYSCALL + if (flags & ~(FANOTIFY_INIT_FLAGS | FAN_ENABLE_AUDIT)) +#else + if (flags & ~FANOTIFY_INIT_FLAGS) +#endif + return -EINVAL; + + if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS) + return -EINVAL; + + switch (event_f_flags & O_ACCMODE) { + case O_RDONLY: + case O_RDWR: + case O_WRONLY: + break; + default: + return -EINVAL; + } + + if (fid_mode && class != FAN_CLASS_NOTIF) + return -EINVAL; + + /* + * Child name is reported with parent fid so requires dir fid. + * We can report both child fid and dir fid with or without name. + */ + if ((fid_mode & FAN_REPORT_NAME) && !(fid_mode & FAN_REPORT_DIR_FID)) + return -EINVAL; + + user = get_current_user(); + if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) { + free_uid(user); + return -EMFILE; + } + + f_flags = O_RDWR | FMODE_NONOTIFY; + if (flags & FAN_CLOEXEC) + f_flags |= O_CLOEXEC; + if (flags & FAN_NONBLOCK) + f_flags |= O_NONBLOCK; + + /* fsnotify_alloc_group takes a ref. Dropped in fanotify_release */ + group = fsnotify_alloc_group(&fanotify_fsnotify_ops); + if (IS_ERR(group)) { + free_uid(user); + return PTR_ERR(group); + } + + group->fanotify_data.user = user; + group->fanotify_data.flags = flags; + atomic_inc(&user->fanotify_listeners); + group->memcg = get_mem_cgroup_from_mm(current->mm); + + group->overflow_event = fanotify_alloc_overflow_event(); + if (unlikely(!group->overflow_event)) { + fd = -ENOMEM; + goto out_destroy_group; + } + + if (force_o_largefile()) + event_f_flags |= O_LARGEFILE; + group->fanotify_data.f_flags = event_f_flags; + init_waitqueue_head(&group->fanotify_data.access_waitq); + INIT_LIST_HEAD(&group->fanotify_data.access_list); + switch (class) { + case FAN_CLASS_NOTIF: + group->priority = FS_PRIO_0; + break; + case FAN_CLASS_CONTENT: + group->priority = FS_PRIO_1; + break; + case FAN_CLASS_PRE_CONTENT: + group->priority = FS_PRIO_2; + break; + default: + fd = -EINVAL; + goto out_destroy_group; + } + + if (flags & FAN_UNLIMITED_QUEUE) { + fd = -EPERM; + if (!capable(CAP_SYS_ADMIN)) + goto out_destroy_group; + group->max_events = UINT_MAX; + } else { + group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS; + } + + if (flags & FAN_UNLIMITED_MARKS) { + fd = -EPERM; + if (!capable(CAP_SYS_ADMIN)) + goto out_destroy_group; + group->fanotify_data.max_marks = UINT_MAX; + } else { + group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS; + } + + if (flags & FAN_ENABLE_AUDIT) { + fd = -EPERM; + if (!capable(CAP_AUDIT_WRITE)) + goto out_destroy_group; + } + + fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags); + if (fd < 0) + goto out_destroy_group; + + return fd; + +out_destroy_group: + fsnotify_destroy_group(group); + return fd; +} + +/* Check if filesystem can encode a unique fid */ +static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid) +{ + __kernel_fsid_t root_fsid; + int err; + + /* + * Make sure path is not in filesystem with zero fsid (e.g. tmpfs). + */ + err = vfs_get_fsid(path->dentry, fsid); + if (err) + return err; + + if (!fsid->val[0] && !fsid->val[1]) + return -ENODEV; + + /* + * Make sure path is not inside a filesystem subvolume (e.g. btrfs) + * which uses a different fsid than sb root. + */ + err = vfs_get_fsid(path->dentry->d_sb->s_root, &root_fsid); + if (err) + return err; + + if (root_fsid.val[0] != fsid->val[0] || + root_fsid.val[1] != fsid->val[1]) + return -EXDEV; + + /* + * We need to make sure that the file system supports at least + * encoding a file handle so user can use name_to_handle_at() to + * compare fid returned with event to the file handle of watched + * objects. However, name_to_handle_at() requires that the + * filesystem also supports decoding file handles. + */ + if (!path->dentry->d_sb->s_export_op || + !path->dentry->d_sb->s_export_op->fh_to_dentry) + return -EOPNOTSUPP; + + return 0; +} + +static int fanotify_events_supported(struct path *path, __u64 mask, + unsigned int flags) +{ + unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS; + + /* + * Some filesystems such as 'proc' acquire unusual locks when opening + * files. For them fanotify permission events have high chances of + * deadlocking the system - open done when reporting fanotify event + * blocks on this "unusual" lock while another process holding the lock + * waits for fanotify permission event to be answered. Just disallow + * permission events for such filesystems. + */ + if (mask & FANOTIFY_PERM_EVENTS && + path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM) + return -EINVAL; + + /* + * mount and sb marks are not allowed on kernel internal pseudo fs, + * like pipe_mnt, because that would subscribe to events on all the + * anonynous pipes in the system. + * + * SB_NOUSER covers all of the internal pseudo fs whose objects are not + * exposed to user's mount namespace, but there are other SB_KERNMOUNT + * fs, like nsfs, debugfs, for which the value of allowing sb and mount + * mark is questionable. For now we leave them alone. + */ + if (mark_type != FAN_MARK_INODE && + path->mnt->mnt_sb->s_flags & SB_NOUSER) + return -EINVAL; + + return 0; +} + +static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, + int dfd, const char __user *pathname) +{ + struct inode *inode = NULL; + struct vfsmount *mnt = NULL; + struct fsnotify_group *group; + struct fd f; + struct path path; + __kernel_fsid_t __fsid, *fsid = NULL; + u32 valid_mask = FANOTIFY_EVENTS | FANOTIFY_EVENT_FLAGS; + unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS; + bool ignored = flags & FAN_MARK_IGNORED_MASK; + unsigned int obj_type, fid_mode; + u32 umask = 0; + int ret; + + pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n", + __func__, fanotify_fd, flags, dfd, pathname, mask); + + /* we only use the lower 32 bits as of right now. */ + if (mask & ((__u64)0xffffffff << 32)) + return -EINVAL; + + if (flags & ~FANOTIFY_MARK_FLAGS) + return -EINVAL; + + switch (mark_type) { + case FAN_MARK_INODE: + obj_type = FSNOTIFY_OBJ_TYPE_INODE; + break; + case FAN_MARK_MOUNT: + obj_type = FSNOTIFY_OBJ_TYPE_VFSMOUNT; + break; + case FAN_MARK_FILESYSTEM: + obj_type = FSNOTIFY_OBJ_TYPE_SB; + break; + default: + return -EINVAL; + } + + switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) { + case FAN_MARK_ADD: + case FAN_MARK_REMOVE: + if (!mask) + return -EINVAL; + break; + case FAN_MARK_FLUSH: + if (flags & ~(FANOTIFY_MARK_TYPE_BITS | FAN_MARK_FLUSH)) + return -EINVAL; + break; + default: + return -EINVAL; + } + + if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) + valid_mask |= FANOTIFY_PERM_EVENTS; + + if (mask & ~valid_mask) + return -EINVAL; + + /* Event flags (ONDIR, ON_CHILD) are meaningless in ignored mask */ + if (ignored) + mask &= ~FANOTIFY_EVENT_FLAGS; + + f = fdget(fanotify_fd); + if (unlikely(!f.file)) + return -EBADF; + + /* verify that this is indeed an fanotify instance */ + ret = -EINVAL; + if (unlikely(f.file->f_op != &fanotify_fops)) + goto fput_and_out; + group = f.file->private_data; + + /* + * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF. These are not + * allowed to set permissions events. + */ + ret = -EINVAL; + if (mask & FANOTIFY_PERM_EVENTS && + group->priority == FS_PRIO_0) + goto fput_and_out; + + /* + * Events with data type inode do not carry enough information to report + * event->fd, so we do not allow setting a mask for inode events unless + * group supports reporting fid. + * inode events are not supported on a mount mark, because they do not + * carry enough information (i.e. path) to be filtered by mount point. + */ + fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS); + if (mask & FANOTIFY_INODE_EVENTS && + (!fid_mode || mark_type == FAN_MARK_MOUNT)) + goto fput_and_out; + + if (flags & FAN_MARK_FLUSH) { + ret = 0; + if (mark_type == FAN_MARK_MOUNT) + fsnotify_clear_vfsmount_marks_by_group(group); + else if (mark_type == FAN_MARK_FILESYSTEM) + fsnotify_clear_sb_marks_by_group(group); + else + fsnotify_clear_inode_marks_by_group(group); + goto fput_and_out; + } + + ret = fanotify_find_path(dfd, pathname, &path, flags, + (mask & ALL_FSNOTIFY_EVENTS), obj_type); + if (ret) + goto fput_and_out; + + if (flags & FAN_MARK_ADD) { + ret = fanotify_events_supported(&path, mask, flags); + if (ret) + goto path_put_and_out; + } + + if (fid_mode) { + ret = fanotify_test_fid(&path, &__fsid); + if (ret) + goto path_put_and_out; + + fsid = &__fsid; + } + + /* inode held in place by reference to path; group by fget on fd */ + if (mark_type == FAN_MARK_INODE) + inode = path.dentry->d_inode; + else + mnt = path.mnt; + + /* Mask out FAN_EVENT_ON_CHILD flag for sb/mount/non-dir marks */ + if (mnt || !S_ISDIR(inode->i_mode)) { + mask &= ~FAN_EVENT_ON_CHILD; + umask = FAN_EVENT_ON_CHILD; + /* + * If group needs to report parent fid, register for getting + * events with parent/name info for non-directory. + */ + if ((fid_mode & FAN_REPORT_DIR_FID) && + (flags & FAN_MARK_ADD) && !ignored) + mask |= FAN_EVENT_ON_CHILD; + } + + /* create/update an inode mark */ + switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE)) { + case FAN_MARK_ADD: + if (mark_type == FAN_MARK_MOUNT) + ret = fanotify_add_vfsmount_mark(group, mnt, mask, + flags, fsid); + else if (mark_type == FAN_MARK_FILESYSTEM) + ret = fanotify_add_sb_mark(group, mnt->mnt_sb, mask, + flags, fsid); + else + ret = fanotify_add_inode_mark(group, inode, mask, + flags, fsid); + break; + case FAN_MARK_REMOVE: + if (mark_type == FAN_MARK_MOUNT) + ret = fanotify_remove_vfsmount_mark(group, mnt, mask, + flags, umask); + else if (mark_type == FAN_MARK_FILESYSTEM) + ret = fanotify_remove_sb_mark(group, mnt->mnt_sb, mask, + flags, umask); + else + ret = fanotify_remove_inode_mark(group, inode, mask, + flags, umask); + break; + default: + ret = -EINVAL; + } + +path_put_and_out: + path_put(&path); +fput_and_out: + fdput(f); + return ret; +} + +#ifndef CONFIG_ARCH_SPLIT_ARG64 +SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags, + __u64, mask, int, dfd, + const char __user *, pathname) +{ + return do_fanotify_mark(fanotify_fd, flags, mask, dfd, pathname); +} +#endif + +#if defined(CONFIG_ARCH_SPLIT_ARG64) || defined(CONFIG_COMPAT) +SYSCALL32_DEFINE6(fanotify_mark, + int, fanotify_fd, unsigned int, flags, + SC_ARG64(mask), int, dfd, + const char __user *, pathname) +{ + return do_fanotify_mark(fanotify_fd, flags, SC_VAL64(__u64, mask), + dfd, pathname); +} +#endif + +/* + * fanotify_user_setup - Our initialization function. Note that we cannot return + * error because we have compiled-in VFS hooks. So an (unlikely) failure here + * must result in panic(). + */ +static int __init fanotify_user_setup(void) +{ + BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 10); + BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9); + + fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, + SLAB_PANIC|SLAB_ACCOUNT); + fanotify_fid_event_cachep = KMEM_CACHE(fanotify_fid_event, + SLAB_PANIC); + fanotify_path_event_cachep = KMEM_CACHE(fanotify_path_event, + SLAB_PANIC); + if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS)) { + fanotify_perm_event_cachep = + KMEM_CACHE(fanotify_perm_event, SLAB_PANIC); + } + + return 0; +} +device_initcall(fanotify_user_setup); |