linux-kernel - Re: [AppArmor 32/45] Enable LSM hooks to distinguish operations on file descriptors from operations on pathnames

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Message-Id: <200710262224.45773.agruen@suse.de>
Date:	Fri, 26 Oct 2007 22:24:45 +0200
From:	Andreas Gruenbacher <agruen@...e.de>
To:	Miklos Szeredi <mszeredi@...e.cz>
Cc:	jjohansen@...e.de, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: Re: [AppArmor 32/45] Enable LSM hooks to distinguish operations on file descriptors from operations on pathnames

On Friday 26 October 2007 13:30, Miklos Szeredi wrote:
> There's a slight problem (other than HCH not liking it) with this
> approach of passing the open file in iattr:  for special files, the
> struct file pointer makes no sense to the filesystem, since it is always
> opened by the generic functions.

So what do you think where the inodes come from for syscalls like fchmod? Out 
of struct file, of course. But your f_op->getattr and f_op->setattr patches 
are meant for passing struct file down to filesystems anyway, so that 
completely contradicts what you are saying above.

> So I think the correct solution (which was suggested by Trond and
> others) is to define an f_op->fsetattr() method, which interested
> filesystems can define.

That's nothing but a replacement for ATTR_FILE and iattr->ia_file. Except by 
removing the ATTR_FILE flag, LSMs will no longer get that information for 
distinguishing file descriptor operations from other operations.

AppArmor needs to know when notify_change is called on a file descriptor, but 
it doesn't care about the file descriptor itself. So any way of passing along 
that information will be fine.

Thanks,
Andreas
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