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Date:   Thu, 18 Feb 2021 09:47:34 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To:     "Enrico Weigelt, metux IT consult" <info@metux.net>
Cc:     linux-kernel@vger.kernel.org, pmladek@suse.com,
        rostedt@goodmis.org, sergey.senozhatsky@gmail.com,
        andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk,
        kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
        john.fastabend@gmail.com, kpsingh@kernel.org,
        netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH] lib: vsprintf: check for NULL device_node name in
 device_node_string()
Message-ID: <YC25JlDIPl30xPab@jagdpanzerIV.localdomain>
References: <20210217121543.13010-1-info@metux.net>
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On (21/02/17 13:15), Enrico Weigelt, metux IT consult wrote:
> Under rare circumstances it may happen that a device node's name is NULL
> (most likely kernel bug in some other place). In such situations anything
> but helpful, if the debug printout crashes, and nobody knows what actually
> happened here.
> 
> Therefore protect it by an explicit NULL check and print out an extra
> warning.
> 
> Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
> ---
>  lib/vsprintf.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 3b53c73580c5..050a60b88073 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -2013,6 +2013,10 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
>  			break;
>  		case 'n':	/* name */
>  			p = fwnode_get_name(of_fwnode_handle(dn));
> +			if (!p) {
> +				pr_warn("device_node without name. Kernel bug ?\n");
> +				p = "<NULL>";
> +			}
>  			precision = str_spec.precision;
>  			str_spec.precision = strchrnul(p, '@') - p;
>  			buf = string(buf, end, p, str_spec);

What about other fwnode_get_name() calls in vsprintf?

	-ss