Re: [PATCH] BSD Secure Levels: claim block dev in file struct rather than inode struct, 2.6.11-rc2-mm1 (3/8)

Serge E. Hallyn
2005-02-08T20:10:03Z

Quoting Valdis.Kletnieks@vt.edu (Valdis.Kletnieks@vt.edu):
> On Tue, 08 Feb 2005 11:24:50 CST, Michael Halcrow said:
>
> > While the program is waiting for a keystroke, mount the block device.
> > Enter a keystroke. The result without the patch is 1, which is a
> > security violation. This occurs because the bd_release function will
> > bd_release(bdev) and set inode->i_security to NULL on the close(fd1).
>
> Sounds like a bug, not a feature. Should it be zeroing out inode->i_security
> for an inode with a non-zero reference count?

Valdis,

inode->i_security is no longer used after the patch. Does your question
still apply with the proposed patch, %s/inode->i_security/file->f_security/?

Nevertheless, note that the thing being enforced is "no simultaneous
write access to a block device and mount of that block device." The
file->f_security is just used as a flag to seclvl that when this file
is closed, we can bd_release the device to allow a mount or another
open(O_RDWR) of the file. So references to the inode don't matter,
provided the other references are read accesses. Which they have to
be, since otherwise the seclvl_bd_claim() would have failed on the
second open(O_RDWR) call.

I hope I'm at least remotely answering your question :)

-serge