From a8b13aa20afb69161b5123b4f1acc7ea0a03d360 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Thu, 10 Jan 2019 19:04:36 +0200 Subject: fanotify: enable FAN_REPORT_FID init flag When setting up an fanotify listener, user may request to get fid information in event instead of an open file descriptor. The fid obtained with event on a watched object contains the file handle returned by name_to_handle_at(2) and fsid returned by statfs(2). Restrict FAN_REPORT_FID to class FAN_CLASS_NOTIF, because we have have no good reason to support reporting fid on permission events. When setting a mark, we need to make sure that the filesystem supports encoding file handles with name_to_handle_at(2) and that statfs(2) encodes a non-zero fsid. Cc: Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara --- fs/notify/fanotify/fanotify_user.c | 61 +++++++++++++++++++++++++++++++++++++- 1 file changed, 60 insertions(+), 1 deletion(-) (limited to 'fs/notify') diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index cd82dd713c91..1638c171ca82 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -17,6 +17,8 @@ #include #include #include +#include +#include #include @@ -768,6 +770,10 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) return -EINVAL; } + if ((flags & FAN_REPORT_FID) && + (flags & FANOTIFY_CLASS_BITS) != FAN_CLASS_NOTIF) + return -EINVAL; + user = get_current_user(); if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) { free_uid(user); @@ -854,6 +860,52 @@ out_destroy_group: return fd; } +/* Check if filesystem can encode a unique fid */ +static int fanotify_test_fid(struct path *path) +{ + struct kstatfs stat, root_stat; + struct path root = { + .mnt = path->mnt, + .dentry = path->dentry->d_sb->s_root, + }; + int err; + + /* + * Make sure path is not in filesystem with zero fsid (e.g. tmpfs). + */ + err = vfs_statfs(path, &stat); + if (err) + return err; + + if (!stat.f_fsid.val[0] && !stat.f_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_statfs(&root, &root_stat); + if (err) + return err; + + if (root_stat.f_fsid.val[0] != stat.f_fsid.val[0] || + root_stat.f_fsid.val[1] != stat.f_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 do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, int dfd, const char __user *pathname) { @@ -939,6 +991,12 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, if (ret) goto fput_and_out; + if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) { + ret = fanotify_test_fid(&path); + if (ret) + goto path_put_and_out; + } + /* inode held in place by reference to path; group by fget on fd */ if (mark_type == FAN_MARK_INODE) inode = path.dentry->d_inode; @@ -967,6 +1025,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, ret = -EINVAL; } +path_put_and_out: path_put(&path); fput_and_out: fdput(f); @@ -1003,7 +1062,7 @@ COMPAT_SYSCALL_DEFINE6(fanotify_mark, */ static int __init fanotify_user_setup(void) { - BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 7); + BUILD_BUG_ON(HWEIGHT32(FANOTIFY_INIT_FLAGS) != 8); BUILD_BUG_ON(HWEIGHT32(FANOTIFY_MARK_FLAGS) != 9); fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, -- cgit v1.2.3-55-g7522