linux-kernel - Re: [PATCH] IMA: policy can be updated zero times

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Date:	Tue, 22 Dec 2015 14:56:28 -0500
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	dmitry.kasatkin@...il.com, james.l.morris@...cle.com,
	serge@...lyn.com, linux-ima-devel@...ts.sourceforge.net,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, petkan@...-labs.com
Subject: Re: [PATCH] IMA: policy can be updated zero times

On Tue, 2015-12-22 at 08:51 -0500, Sasha Levin wrote:
> Commit "IMA: policy can now be updated multiple times" assumed that the
> policy would be updated at least once.
> 
> If there are zero updates, the temporary list head object will get added
> to the policy list, and later dereferenced as an IMA policy object, which
> means that invalid memory will be accessed.
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  security/integrity/ima/ima_policy.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index ba5d2fc..9b958b8 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -431,6 +431,9 @@ void ima_update_policy(void)
>  {
>  	struct list_head *first, *last, *policy;
> 
> +	if (list_empty(&ima_temp_rules))
> +		return;
> +
>  	/* append current policy with the new rules */
>  	first = (&ima_temp_rules)->next;
>  	last = (&ima_temp_rules)->prev;

Thanks, Sasha.  By the time ima_update_policy() is called
ima_release_policy() has already output the policy update status
message.  I guess an empty policy could be considered a valid policy.
Could you add a msg indicating that the new policy was empty?

Mimi

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