linux-hardening - Re: [PATCH] btrfs: sysfs: Handle NULL return values

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Message-ID: <Y99XGrFvXBL32cOO@kroah.com>
Date:   Sun, 5 Feb 2023 08:13:30 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] btrfs: sysfs: Handle NULL return values

On Sat, Feb 04, 2023 at 10:35:10AM -0800, Kees Cook wrote:
> Each of to_fs_info(), discard_to_fs_info(), and to_space_info() can
> return NULL values.

The code says it could, but I really do not think that is possible at
all, especially based on the fact that there have never been any crashes
reported here.

So the NULL returns should just be removed instead, right?

Also, to_space_info() is a macro of container_of() which can not return
NULL.

And get_btrfs_kobj() is just odd, that probably should be fixed up as
well, that's an indication that something is wrong with the sysfs code
if anyone has to attempt to walk the whole kobject parent path :(

So while this patch might fix up the compiler warning, it's logically
not going to change anything, let's fix this properly.  I can look at it
next week if someone doesn't beat me to it.

thanks,

greg k-h