Messages in this thread | | | From | David Howells <> | Subject | Are path-based LSM hooks called from the wrong places? | Date | Wed, 25 Mar 2009 16:14:13 +0000 |
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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
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