From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757149AbbIUTEr (ORCPT ); Mon, 21 Sep 2015 15:04:47 -0400 Received: from mga09.intel.com ([134.134.136.24]:23224 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756201AbbIUTEk (ORCPT ); Mon, 21 Sep 2015 15:04:40 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.17,568,1437462000"; d="scan'208";a="809729869" Subject: [PATCH] inotify: hide internal kernel bits from fdinfo To: dave@sr71.net Cc: dave.hansen@linux.intel.com, avagin@gmail.com, akpm@linux-foundation.org, gorcunov@openvz.org, xemul@parallels.com, eparis@redhat.com, john@johnmccutchan.com, rlove@rlove.org, linux-kernel@vger.kernel.org From: Dave Hansen Date: Mon, 21 Sep 2015 11:45:01 -0700 Message-Id: <20150921184501.E0313E5A@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen There was a report that my patch: inotify: actually check for invalid bits in sys_inotify_add_watch() broke CRIU. The reason is that CRIU looks up raw flags in /proc/$pid/fdinfo/* to figure out how to rebuild inotify watches and then passes those flags directly back in to the inotify API. One of those flags (FS_EVENT_ON_CHILD) is set in mark->mask, but is not part of the inotify API. It is used inside the kernel to _implement_ inotify but it is not and has never been part of the API. My patch above ensured that we only allow bits which are part of the API (IN_ALL_EVENTS). This broke CRIU. FS_EVENT_ON_CHILD is really internal to the kernel. It is set _anyway_ on all inotify marks. So, CRIU was really just trying to set a bit that was already set. This patch hides that bit from fdinfo. CRIU will not see the bit, not try to set it, and should work as before. We should not have been exposing this bit in the first place, so this is a good patch independent of the CRIU problem. Signed-off-by: Dave Hansen Reported-by: Andrey Wagin Cc: Andrew Morton Cc: Cyrill Gorcunov Cc: xemul@parallels.com Cc: Eric Paris Cc: john@johnmccutchan.com Cc: rlove@rlove.org Cc: linux-kernel@vger.kernel.org --- b/fs/notify/fdinfo.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff -puN fs/notify/fdinfo.c~fdinfo-mask fs/notify/fdinfo.c --- a/fs/notify/fdinfo.c~fdinfo-mask 2015-09-21 10:24:01.031864268 -0700 +++ b/fs/notify/fdinfo.c 2015-09-21 10:25:04.335723826 -0700 @@ -82,9 +82,16 @@ static void inotify_fdinfo(struct seq_fi inode_mark = container_of(mark, struct inotify_inode_mark, fsn_mark); inode = igrab(mark->inode); if (inode) { + /* + * IN_ALL_EVENTS represents all of the mask bits + * that we expose to userspace. There is at + * least one bit (FS_EVENT_ON_CHILD) which is + * used only internally to the kernel. + */ + u32 mask = mark->mask & IN_ALL_EVENTS; seq_printf(m, "inotify wd:%x ino:%lx sdev:%x mask:%x ignored_mask:%x ", inode_mark->wd, inode->i_ino, inode->i_sb->s_dev, - mark->mask, mark->ignored_mask); + mask, mark->ignored_mask); show_mark_fhandle(m, inode); seq_putc(m, '\n'); iput(inode); _