linux-kernel - RE: [PATCH] usb: dwc3: free dwc->regset on dwc3_debugfs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 11 Apr 2016 15:09:34 +0300
From:	Felipe Balbi <balbi@...nel.org>
To:	"Du\, Changbin" <changbin.du@...el.com>
Cc:	"gregkh\@linuxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb\@vger.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] usb: dwc3: free dwc->regset on dwc3_debugfs_exit


Hi,

"Du, Changbin" <changbin.du@...el.com> writes:
>> 
>> >> > +	dwc->regset = NULL;
>> >>
>> >> setting regset to NULL is unnecessary. We only call dwc3_debugfs_exit()
>> >> when removing the driver.
>> >>
>> >> --
>> >> Balbi
>> > I'd like keep this line even it is unnecessary, because It is a good habit to
>> > Avoid wild pointers. Just like the dwc->root = NULL.
>> 
>> there won't be any wild pointers here, we'll free struct dwc3 *dwc itself.
>> 
>> --
>> Balbi
> I agree the dwc will be freed in current code. But the 'free' logical is out
> of the debugfs code. They should be treat as some logical independent. Per
> this point, I still think set pointer to null is not bad. For example, if dwc3 core
> code invoke dwc3_debugfs_exit twice by mistake(just an example case, not
> really), then no crash/impact for the second call.

the second call should crash because it's clearly wrong ;-) If dwc3 ever
calls dwc3_debugfs_exit() twice, it really deserves to crash. It's
something so wrong that we want the verbosity and urgency of a kernel
oops to make sure we fix it ASAP.

If, however, we set it to null, it might be years before we notice
anything's wrong.

-- 
balbi

Download attachment "signature.asc" of type "application/pgp-signature" (819 bytes)