[ 3.5.y.z extended stable ] Patch "inotify: remove broken mask checks causing unmount to be" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    inotify: remove broken mask checks causing unmount to be

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 3e4a55ddcb7bdb59a1181b75a24a7717509d44ce Mon Sep 17 00:00:00 2001
From: Jim Somerville <Jim.Somerville at windriver.com>
Date: Thu, 21 Feb 2013 16:41:59 -0800
Subject: [PATCH] inotify: remove broken mask checks causing unmount to be
 EINVAL

commit 676a0675cf9200ac047fb50825f80867b3bb733b upstream.

Running the command:

	inotifywait -e unmount /mnt/disk

immediately aborts with a -EINVAL return code.  This is however a valid
parameter.  This abort occurs only if unmount is the sole event
parameter.  If other event parameters are supplied, then the unmount
event wait will work.

The problem was introduced by commit 44b350fc23e ("inotify: Fix mask
checks").  In that commit, it states:

	The mask checks in inotify_update_existing_watch() and
	inotify_new_watch() are useless because inotify_arg_to_mask()
	sets FS_IN_IGNORED and FS_EVENT_ON_CHILD bits anyway.

But instead of removing the useless checks, it did this:

	        mask = inotify_arg_to_mask(arg);
	-       if (unlikely(!mask))
	+       if (unlikely(!(mask & IN_ALL_EVENTS)))
	                return -EINVAL;

The problem is that IN_ALL_EVENTS doesn't include IN_UNMOUNT, and other
parts of the code keep IN_UNMOUNT separate from IN_ALL_EVENTS.  So the
check should be:

	if (unlikely(!(mask & (IN_ALL_EVENTS | IN_UNMOUNT))))

But inotify_arg_to_mask(arg) always sets the IN_UNMOUNT bit in the mask
anyway, so the check is always going to pass and thus should simply be
removed.  Also note that inotify_arg_to_mask completely controls what
mask bits get set from arg, there's no way for invalid bits to get
enabled there.

Lets fix it by simply removing the useless broken checks.

Signed-off-by: Jim Somerville <Jim.Somerville at windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker at windriver.com>
Cc: Jerome Marchand <jmarchan at redhat.com>
Cc: John McCutchan <john at johnmccutchan.com>
Cc: Robert Love <rlove at rlove.org>
Cc: Eric Paris <eparis at parisplace.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/notify/inotify/inotify_user.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 8445fbc..6f292dd 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -579,8 +579,6 @@ static int inotify_update_existing_watch(struct fsnotify_group *group,

 	/* don't allow invalid bits: we don't want flags set */
 	mask = inotify_arg_to_mask(arg);
-	if (unlikely(!(mask & IN_ALL_EVENTS)))
-		return -EINVAL;

 	fsn_mark = fsnotify_find_inode_mark(group, inode);
 	if (!fsn_mark)
@@ -632,8 +630,6 @@ static int inotify_new_watch(struct fsnotify_group *group,

 	/* don't allow invalid bits: we don't want flags set */
 	mask = inotify_arg_to_mask(arg);
-	if (unlikely(!(mask & IN_ALL_EVENTS)))
-		return -EINVAL;

 	tmp_i_mark = kmem_cache_alloc(inotify_inode_mark_cachep, GFP_KERNEL);
 	if (unlikely(!tmp_i_mark))
--
1.8.1.2