From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f66.google.com ([209.85.221.66]:33646 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725841AbeLBLiv (ORCPT ); Sun, 2 Dec 2018 06:38:51 -0500 From: Amir Goldstein To: Jan Kara Cc: Matthew Bobrowski , linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org Subject: [PATCH v4 08/15] fanotify: enable FAN_REPORT_FID init flag Date: Sun, 2 Dec 2018 13:38:19 +0200 Message-Id: <20181202113826.32133-9-amir73il@gmail.com> In-Reply-To: <20181202113826.32133-1-amir73il@gmail.com> References: <20181202113826.32133-1-amir73il@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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). 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 --- fs/notify/fanotify/fanotify_user.c | 57 +++++++++++++++++++++++++++++- include/linux/fanotify.h | 2 +- 2 files changed, 57 insertions(+), 2 deletions(-) diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 032a9a225a21..3b8d442e67cd 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 @@ -850,6 +852,52 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags) 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) { @@ -935,6 +983,12 @@ 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; @@ -963,6 +1017,7 @@ 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); @@ -999,7 +1054,7 @@ 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, diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h index 9e2142795335..f59be967f72b 100644 --- a/include/linux/fanotify.h +++ b/include/linux/fanotify.h @@ -19,7 +19,7 @@ FAN_CLASS_PRE_CONTENT) #define FANOTIFY_INIT_FLAGS (FANOTIFY_CLASS_BITS | \ - FAN_REPORT_TID | \ + FAN_REPORT_TID | FAN_REPORT_FID | \ FAN_CLOEXEC | FAN_NONBLOCK | \ FAN_UNLIMITED_QUEUE | FAN_UNLIMITED_MARKS) -- 2.17.1