From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760119AbYDQBP2 (ORCPT ); Wed, 16 Apr 2008 21:15:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759079AbYDQBHi (ORCPT ); Wed, 16 Apr 2008 21:07:38 -0400 Received: from sous-sol.org ([216.99.217.87]:58859 "EHLO sous-sol.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758952AbYDQBHf (ORCPT ); Wed, 16 Apr 2008 21:07:35 -0400 Message-Id: <20080417010317.497463045@sous-sol.org> References: <20080417010122.148289106@sous-sol.org> User-Agent: quilt/0.46-1 Date: Wed, 16 Apr 2008 18:01:31 -0700 From: Chris Wright To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Christian Lamparter , nickpiggin@yahoo.com.au, Nick Piggin , Robert Love , John McCutchan , Jan Kara , Yan Zheng Subject: inotify: fix race Content-Disposition: inline; filename=inotify-fix-race.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -stable review patch. If anyone has any objections, please let us know. --------------------- From: Nick Piggin upstream commit: d599e36a9ea85432587f4550acc113cd7549d12a There is a race between setting an inode's children's "parent watched" flag when placing the first watch on a parent, and instantiating new children of that parent: a child could miss having its flags set by set_dentry_child_flags, but then inotify_d_instantiate might still see !inotify_inode_watched. The solution is to set_dentry_child_flags after adding the watch. Locking is taken care of, because both set_dentry_child_flags and inotify_d_instantiate hold dcache_lock and child->d_locks. Signed-off-by: Nick Piggin Cc: Robert Love Cc: John McCutchan Cc: Jan Kara Cc: Yan Zheng Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Cc: Christian Lamparter Signed-off-by: Chris Wright --- fs/inotify.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) --- a/fs/inotify.c +++ b/fs/inotify.c @@ -627,6 +627,7 @@ s32 inotify_add_watch(struct inotify_han struct inode *inode, u32 mask) { int ret = 0; + int newly_watched; /* don't allow invalid bits: we don't want flags set */ mask &= IN_ALL_EVENTS | IN_ONESHOT; @@ -653,12 +654,18 @@ s32 inotify_add_watch(struct inotify_han */ watch->inode = igrab(inode); - if (!inotify_inode_watched(inode)) - set_dentry_child_flags(inode, 1); - /* Add the watch to the handle's and the inode's list */ + newly_watched = !inotify_inode_watched(inode); list_add(&watch->h_list, &ih->watches); list_add(&watch->i_list, &inode->inotify_watches); + /* + * Set child flags _after_ adding the watch, so there is no race + * windows where newly instantiated children could miss their parent's + * watched flag. + */ + if (newly_watched) + set_dentry_child_flags(inode, 1); + out: mutex_unlock(&ih->mutex); mutex_unlock(&inode->inotify_mutex); --