linux-kernel - Re: [PATCH] fsnotify: Fix handling of renames in audit

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Message-ID: <20150211063658.GA30939@quack.suse.cz>
Date:	Wed, 11 Feb 2015 07:36:58 +0100
From:	Jan Kara <jack@...e.cz>
To:	Paul Moore <paul@...l-moore.com>
Cc:	Jan Kara <jack@...e.cz>, Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-audit@...hat.com,
	Eric Paris <eparis@...hat.com>, stable@...r.kernel.org
Subject: Re: [PATCH] fsnotify: Fix handling of renames in audit

On Tue 10-02-15 19:58:35, Paul Moore wrote:
> On Tuesday, February 10, 2015 04:00:12 PM Jan Kara wrote:
> > Commit e9fd702a58c4 (audit: convert audit watches to use fsnotify
> > instead of inotify) broke handling of renames in audit. Audit code wants
> > to update inode number of an inode corresponding to watched name in a
> > directory. When something gets renamed into a directory to a watched
> > name, inotify previously passed moved inode to audit code however new
> > fsnotify code passes directory inode where the change happened. That
> > confuses audit and it starts watching parent directory instead of a file
> > in a directory.
> > 
> > This can be observed for example by doing:
> > cd /tmp
> > touch foo bar
> > auditctl -w /tmp/foo
> > touch foo
> > mv bar foo
> > touch foo
> > 
> > In audit log we see events like:
> > type=CONFIG_CHANGE msg=audit(1423563584.155:90): auid=1000 ses=2
> > op="updated rules" path="/tmp/foo" key=(null) list=4 res=1
> > ...
> > type=PATH msg=audit(1423563584.155:91): item=2 name="bar" inode=1046884
> > dev=08:0
> > 2 mode=0100644 ouid=0 ogid=0 rdev=00:00 nametype=DELETE
> > type=PATH msg=audit(1423563584.155:91): item=3 name="foo" inode=1046842
> > dev=08:0
> > 2 mode=0100644 ouid=0 ogid=0 rdev=00:00 nametype=DELETE
> > type=PATH msg=audit(1423563584.155:91): item=4 name="foo" inode=1046884
> > dev=08:0
> > 2 mode=0100644 ouid=0 ogid=0 rdev=00:00 nametype=CREATE
> > ...
> > and that's it - we see event for the first touch after creating the
> > audit rule, we see events for rename but we don't see any event for the
> > last touch. However we start seeing events for unrelated stuff happening
> > in /tmp.
> > 
> > Fix the problem by passing moved inode as data in the FS_MOVED_FROM and
> > FS_MOVED_TO events instead of the directory where the change happens.
> > This doesn't introduce any new problems because noone besides
> > audit_watch.c cares about the passed value:
> > fs/notify/fanotify/fanotify.c cares only about FSNOTIFY_EVENT_PATH events.
> > fs/notify/dnotify/dnotify.c doesn't care about passed 'data' value at all.
> > fs/notify/inotify/inotify_fsnotify.c uses 'data' only for
> > FSNOTIFY_EVENT_PATH. kernel/audit_tree.c doesn't care about passed 'data'
> > at all.
> > kernel/audit_watch.c expects moved inode as 'data'.
> > 
> > CC: linux-audit@...hat.com
> > CC: Paul Moore <paul@...l-moore.com>
> > CC: Eric Paris <eparis@...hat.com>
> > CC: stable@...r.kernel.org
> > Fixes: e9fd702a58c49dbb14481dca88dad44758da393a
> > Signed-off-by: Jan Kara <jack@...e.cz>
> > ---
> >  include/linux/fsnotify.h | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> I can confirm this is indeed broken.
> 
> Thanks for the patch.  I'm building a test kernel as I type this, assuming all 
> goes well I'll send this to Linus with the other audit patches for v3.20.
  Actually, Andrew has picked up the patch and already sent it to Linus.
So you don't have to put it in your tree. I sent it to Andrew since he
usually takes care of pushing fsnotify fixes to Linus and although this was
an audit bug, the problem was really in fsnotify...

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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