linux-kernel - Re: [PATCH] lib: vsprintf: check for NULL device_node name in device_node

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Date:   Tue, 23 Feb 2021 20:54:16 +0100
From:   "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Enrico Weigelt, metux IT consult" <info@...ux.net>
Cc:     linux-kernel@...r.kernel.org, pmladek@...e.com,
        rostedt@...dmis.org, sergey.senozhatsky@...il.com,
        linux@...musvillemoes.dk, kafai@...com, songliubraving@...com,
        yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH] lib: vsprintf: check for NULL device_node name in
 device_node_string()

On 17.02.21 14:50, Andy Shevchenko wrote:
> On Wed, Feb 17, 2021 at 01:15:43PM +0100, 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).
> 
> What circumstances? How can I reproduce this? More information, please!

Observed it when applying a broken overlay. (sorry, didn't keep that
broken code :o). In this case, the device_node was left without a name
(pointing to NULL).

>> +				pr_warn("device_node without name. Kernel bug ?\n");
> 
> If it's not once, then it's possible to have log spammed with this, right?

It only has occoured once for me. I don't think spamming could happen,
unless one's hacking deeply in the oftree code.

>> +				p = "<NULL>";
> 
> We have different standard de facto for NULL pointers to be printed. Actually
> if you wish, you may gather them under one definition (maybe somewhere under
> printk) and export to everybody to use.

Seen it in Petr's reply ... going to use that in v2.

--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@...ux.net -- +49-151-27565287