linux-kernel - Re: [PATCH] ima: Fix potential NULL pointer access in ima_match

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Date:   Tue, 14 Mar 2023 20:17:02 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roman Danilov <romanosauce57@...il.com>
Cc:     Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Roberto Sassu <roberto.sassu@...wei.com>,
        GUO Zihua <guozihua@...wei.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>
Subject: Re: [PATCH] ima: Fix potential NULL pointer access in
 ima_match_rules()

On Tue, 2023-03-14 at 21:03 +0300, Roman Danilov wrote:
> In ima_match_rules(), when ima_lsm_copy_rule() fails, NULL pointer
> is assigned to lsm_rule. After that, in the next step of the loop
> NULL pointer is dereferenced in lsm_rule->lsm[i].rule.

I must being missing something.  The next step of the loop tests
whether rule_reinitialized is set before accessing lsm_rule-
>lsm[i].rule.

> 
> As far as ima_match_rules() is not designed to return error code,
> add __GFP_NOFAIL to make sure memory allocation succeeds.

Using  __GFP_NOFAIL here would be safer.

> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Fixes: c7423dbdbc9e ("ima: Handle -ESTALE returned by ima_filter_rule_match()")
> Signed-off-by: Roman Danilov <romanosauce57@...il.com>
> Reviewed-by: Alexey Khoroshilov <khoroshilov@...ras.ru>

-- 
thanks,

Mimi