linux-kernel - Re: [PATCH] vfs: fix IMA lockdep circular locking dependency

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Date:	Wed, 16 May 2012 09:42:11 -0400
From:	Eric Paris <eparis@...isplace.org>
To:	James Morris <jmorris@...ei.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Mimi Zohar <zohar@...ibm.com>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfs: fix IMA lockdep circular locking dependency

On Wed, 2012-05-16 at 21:37 +1000, James Morris wrote:
> On Tue, 15 May 2012, Linus Torvalds wrote:
> 
> > Hmm?
> 
> diff --git a/security/capability.c b/security/capability.c
> index 5bb21b1c448c..9a19c6a54e12 100644
> --- a/security/capability.c
> +++ b/security/capability.c
> @@ -949,7 +949,6 @@ void __init security_fixup_ops(struct 
> security_operations *ops)
>         set_to_cap_if_null(ops, file_alloc_security);
>         set_to_cap_if_null(ops, file_free_security);
>         set_to_cap_if_null(ops, file_ioctl);
> -       set_to_cap_if_null(ops, file_mmap);
>         set_to_cap_if_null(ops, file_mprotect);
>         set_to_cap_if_null(ops, file_lock);
>         set_to_cap_if_null(ops, file_fcntl);
> 
> 
> Do we need to add addr_map to the fixup ops?

No.  His patch works just fine without it.  If you look he uses:

+	if (security_ops->mmap_file) {

Which means since we didn't set an explicit .mmap_file, even with no
other LSM loaded we would be fine.

At the moment I'd rather stick with our usual notation of forcing
capabilities to define every option even if all it does it return 0.  If
Linus thinks it's a good idea to do
if (security_ops->function)
	security_ops->funtion(args);
In the security server we should do that cleanup separately...

-Eric

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