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

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Date:	Tue, 10 Feb 2015 16:00:12 +0100
From:	Jan Kara <jack@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>,
	linux-audit@...hat.com, Paul Moore <paul@...l-moore.com>,
	Eric Paris <eparis@...hat.com>, stable@...r.kernel.org
Subject: [PATCH] fsnotify: Fix handling of renames in audit

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(-)

diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 1c804b057fb1..7ee1774edee5 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -101,8 +101,10 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
 		new_dir_mask |= FS_ISDIR;
 	}

-	fsnotify(old_dir, old_dir_mask, old_dir, FSNOTIFY_EVENT_INODE, old_name, fs_cookie);
-	fsnotify(new_dir, new_dir_mask, new_dir, FSNOTIFY_EVENT_INODE, new_name, fs_cookie);
+	fsnotify(old_dir, old_dir_mask, source, FSNOTIFY_EVENT_INODE, old_name,
+		 fs_cookie);
+	fsnotify(new_dir, new_dir_mask, source, FSNOTIFY_EVENT_INODE, new_name,
+		 fs_cookie);

 	if (target)
 		fsnotify_link_count(target);
-- 
2.1.4

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