Re: Observed unexpected behavior of BTRFS in d_instantiate

[Stephen Smalley <sds@tycho.nsa.gov>]

On Tue, 2011-04-26 at 20:15 -0700, Casey Schaufler wrote:
> 
> I have been tracking down an problem that we've been seeing
> with Smack on top of btrfs and have narrowed it down to a check
> in smack_d_instantiate() that checks to see if the underlying
> filesystem supports extended attributes by looking at
> 
>     inode->i_op->getxattr
> 
> If the filesystem has no entry for getxattr it is assumed that
> it does not support extended attributes. The Smack code clearly
> finds this value to be NULL for btrfs and uses a fallback value.
> Clearly something is amiss, as other code paths clearly find the
> i_op->getxattr function and use it to effect. The btrfs code
> quite obviously includes getxattr functions.
> 
> So, what is btrfs up to such that the inode ops does not include
> getxattr when security_d_instantiate is called? I am led to
> understand that SELinux has worked around this, but looking at
> the SELinux code I expect that there is a problem there as well.
> 
> Thank you.

kernel version(s)?
reproducer?

-- 
Stephen Smalley
National Security Agency