linux-kernel - Re: [PATCH] kobject: Safe return of kobject_get

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Message-ID: <CWXP265MB26809893E168B75CF57ECC86C4079@CWXP265MB2680.GBRP265.PROD.OUTLOOK.COM>
Date:   Thu, 24 Jun 2021 06:42:41 +0000
From:   Christian Löhle <CLoehle@...erstone.com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kobject: Safe return of kobject_get_path with NULL

Hey Greg,

>> Prevent NULL dereference within get_kobj_path_length
>> 
>> Calling kobject_get_path could provoke a NULL dereference
>> if NULL was passed. while fill_kobj_path will return
>> with a sane 0 for NULL, kobjet_get_path_length did not.
>
>Who passes NULL into that function?  Shouldn't that be fixed first?

It seems to me like here specifically it was a sd_open on some no longer
existing device. I agree, but could not find a fix for that, and even if, it might
not have been in the current tree.
But when looking at the kobject code it felt like it was meant to be safe for
NULL, (like any parent in the tree can be NULL), but the do while does hide that
a bit.
So is it not meant to be safe?
I will try to find the sd_open issue some more, but cannot reproduce the issue
consistently enough right now.

>Pleaase always run your patches through checkpatch.pl so you do not get
>maintainers asking you to use checkpatch.pl...

I did, so please tell me what part bothers you, so I can get that fixed, either in v2
or maybe even in checkpatch.pl?
(Only thing I spotted now is the kobjet typo)

Regards,
Christian
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