linux-kernel - Re: [PATCH -next,v2 1/2] audit: fix possible null-pointer dereference in audit_filter

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Date:   Wed, 13 Oct 2021 17:12:38 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Gaosheng Cui <cuigaosheng1@...wei.com>
Cc:     Eric Paris <eparis@...hat.com>, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org, xiujianfeng@...wei.com,
        wangweiyang2@...wei.com
Subject: Re: [PATCH -next,v2 1/2] audit: fix possible null-pointer dereference
 in audit_filter_rules

On Wed, Oct 13, 2021 at 5:10 AM Gaosheng Cui <cuigaosheng1@...wei.com> wrote:
>
> Fix this possible null-pointer dereference in audit_filter_rules.

Thanks for fixing this, just a couple of small comments:

I think you can drop the description text below here, the code snippet
is just a duplicate of the code and the error message is pretty
obvious.

> If ctx is null, a null-pointer dereference will occur:
>     case AUDIT_SADDR_FAM:
>         if (ctx->sockaddr)
>                 ...
>         break;
>
> audit_filter_rules() error: we previously assumed 'ctx' could be null
>
> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Signed-off-by: Gaosheng Cui <cuigaosheng1@...wei.com>

I would also add a Fixes tag, for example:

Fixes: bf361231c295 ("audit: add saddr_fam filter field")

> ---
>  kernel/auditsc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 4ba3b8573ff4..42d4a4320526 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -647,7 +647,7 @@ static int audit_filter_rules(struct task_struct *tsk,
>                         result = audit_comparator(audit_loginuid_set(tsk), f->op, f->val);
>                         break;
>                 case AUDIT_SADDR_FAM:
> -                       if (ctx->sockaddr)
> +                       if (ctx && ctx->sockaddr)
>                                 result = audit_comparator(ctx->sockaddr->ss_family,
>                                                           f->op, f->val);
>                         break;
> --
> 2.30.0

-- 
paul moore
www.paul-moore.com