lkml.org 
[lkml]   [2009]   [Mar]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectAre path-based LSM hooks called from the wrong places?
Date

Hi Kentaro,

I've just been looking at some of the VFS syscall routines, such as
notify_change(), with an eye to calling it from FS-Cache to grow a file. I
see that whilst notify_change() calls the inode-based LSM hooks (as drive
SELinux), it doesn't call the path-based LSM hooks (as drive other security
modules). It leaves that to the callers, such as do_sys_ftruncate().

I see that vfs_mkdir(), for example, is similar, in that vfs_mkdir() - which
I'm calling from FS-Cache - invokes the inode-based LSM hooks, but it bypasses
the path-based LSM hooks as those are called from sys_mkdir().

It would appear that path-based LSM hooks may well be being called from the
wrong places. They were added in:

commit be6d3e56a6b9b3a4ee44a0685e39e595073c6f0d
Author: Kentaro Takeda <takedakn@nttdata.co.jp>
Date: Wed Dec 17 13:24:15 2008 +0900

introduce new LSM hooks where vfsmount is available.

Add new LSM hooks for path-based checks. Call them on directory-modifying
operations at the points where we still know the vfsmount involved.

Signed-off-by: Kentaro Takeda <takedakn@nttdata.co.jp>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Toshiharu Harada <haradats@nttdata.co.jp>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Using sys_mkdir() and suchlike directly from within the kernel would add a lot
of overhead as I'd have to generate a full pathname for each call, whereas
vfs_mkdir() or notify_change() allows me to start from an inode I already
have.

David


\
 
 \ /
  Last update: 2009-03-25 17:17    [from the cache]
©2003-2011 Jasper Spaans