linux-kernel - Re: [PATCH] audit: return on memory error to avoid null pointer dereference

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Message-ID: <20180221065259.k4nj4yio2l5gkcxw@madcap2.tricolour.ca>
Date:   Wed, 21 Feb 2018 01:52:59 -0500
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Paul Moore <paul@...l-moore.com>, Eric Paris <eparis@...hat.com>,
        Steve Grubb <sgrubb@...hat.com>
Subject: Re: [PATCH] audit: return on memory error to avoid null pointer
 dereference

On 2018-02-21 01:47, Richard Guy Briggs wrote:
> If there is a memory allocation error when trying to change an audit
> kernel feature value, the ignored allocation error will trigger a NULL
> pointer dereference oops on subsequent use of that pointer.  Return
> instead.
> 
> See: https://github.com/linux-audit/audit-kernel/issues/76
> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>

Self-NACK.  It was based on local development and won't compile on
upstream.  Fix pending.

> ---
>  kernel/audit.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 196d327..31cb11d 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -1063,6 +1063,8 @@ static void audit_log_feature_change(int which, u32 old_feature, u32 new_feature
>  		return;
>  
>  	ab = audit_log_start(context, GFP_KERNEL, AUDIT_FEATURE_CHANGE);
> +	if (!ab)
> +		return;
>  	audit_log_task_info(ab, current);
>  	audit_log_format(ab, " feature=%s old=%u new=%u old_lock=%u new_lock=%u res=%d",
>  			 audit_feature_names[which], !!old_feature, !!new_feature,
> -- 
> 1.8.3.1
> 

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635