From: Paul Bolle <pebolle@tiscali.nl>
To: Tilman Schmidt <tilman@imap.cc>, netdev@vger.kernel.org
Cc: Peter Hurley <peter@hurleysoftware.com>,
Sasha Levin <sasha.levin@oracle.com>,
syzkaller@googlegroups.com, David Miller <davem@davemloft.net>,
Karsten Keil <isdn@linux-pingi.de>,
isdn4linux@listserv.isdn4linux.de,
gigaset307x-common@lists.sourceforge.net,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] ser_gigaset: fix deallocation of platform device structure
Date: Thu, 10 Dec 2015 12:20:22 +0100 [thread overview]
Message-ID: <1449746422.16068.18.camel@tiscali.nl> (raw)
In-Reply-To: <56680C25.1050704@imap.cc>
On wo, 2015-12-09 at 12:10 +0100, Tilman Schmidt wrote:
> Am 09.12.2015 um 00:12 schrieb Paul Bolle:
> > So what does setting
> > cs->hw.ser->dev.dev.driver_data to NULL just before freeing it buy
> > us?
>
> We're freeing cs->hw.ser, not cs->hw.ser->dev.
> Clearing the reference to cs from the device structure before freeing
> cs guards against possible use-after-free.
>
> > > + kfree(cs->hw.ser);
> > > + cs->hw.ser = NULL;
> >
> > I might be missing something, but what does setting this to NULL buy
> > us here?
>
> Just defensive programming. Guarding against possible use-after-free
> or double-free.
I'm inclined to think this is not the best way to guard against such
nasty bugs. But then again, I'm only a few months into my shift of
looking after the gigaset drivers and haven't had to track down such
bugs yet. But I'd be surprised if many other drivers do it that way and
think this is a job for (tree wide) debugging tools. But, whatever the
merits of our views, we can defer this discussion to some future date.
See below.
> I'm a big fan of one change per patch. If we also want to modify the
> moved code then that should be done in a separate patch. It makes
> bisecting so much easier. Same reason why I separated out patch 3/3.
Fair enough.
Paul Bolle
next prev parent reply other threads:[~2015-12-10 11:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-08 11:00 [PATCH 0/3] ser_gigaset fixes Tilman Schmidt
2015-12-08 11:00 ` [PATCH 1/3] ser_gigaset: fix up NULL checks Tilman Schmidt
2015-12-08 19:45 ` Paul Bolle
2015-12-08 22:16 ` One Thousand Gnomes
2015-12-09 10:45 ` Tilman Schmidt
2015-12-09 12:12 ` One Thousand Gnomes
2015-12-09 19:18 ` Paul Bolle
2015-12-08 11:00 ` [PATCH 3/3] ser_gigaset: remove unnecessary kfree() calls from release method Tilman Schmidt
2015-12-08 23:15 ` Paul Bolle
2015-12-08 11:00 ` [PATCH 2/3] ser_gigaset: fix deallocation of platform device structure Tilman Schmidt
2015-12-08 23:12 ` Paul Bolle
2015-12-09 11:10 ` Tilman Schmidt
2015-12-10 11:20 ` Paul Bolle [this message]
2015-12-10 14:04 ` Peter Hurley
2015-12-12 17:52 ` Tilman Schmidt
2015-12-10 11:31 ` [PATCH 0/3] ser_gigaset fixes Paul Bolle
2015-12-12 18:09 ` Tilman Schmidt
2015-12-12 18:32 ` Paul Bolle
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