From: Gen Zhang <blackgod016574@gmail.com>
To: Johan Hovold <johan@kernel.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] tty_io: Fix a missing-check bug in drivers/tty/tty_io.c
Date: Wed, 22 May 2019 19:24:49 +0800 [thread overview]
Message-ID: <20190522112449.GA6666@zhanggen-UX430UQ> (raw)
In-Reply-To: <20190522111949.GB568@localhost>
On Wed, May 22, 2019 at 01:19:49PM +0200, Johan Hovold wrote:
> On Wed, May 22, 2019 at 07:13:54PM +0800, Gen Zhang wrote:
> > On Wed, May 22, 2019 at 12:29:00PM +0200, Johan Hovold wrote:
> > > Where do you see that the kernel is dereferencing tty->dev without
> > > checking for NULL first? If you can find that, then that would indeed be
> > > a bug that needs fixing.
> > Thanks for your reply, Johan!
> > I examined the code but failed to find this situation.
>
> Ok, so your claim in the commit message was incorrect:
>
> And tty->dev is dereferenced in the following codes.
>
> > Anyway, checking return value of tty_get_device() is theoritically
> > right. But tty->dev is never dereferenced, so checking is not needed.
>
> No, sorry, it's not even theoretically correct. Our current code depends
> on tty->dev sometimes being NULL. Your patch would specifically break
> pseudo terminals.
Thanks for your comments. I have to be very proficient in this module
to know this. Of course I am not.
Anyway, appreciate your replies, Johan.
Thanks
Gen
>
> > However, what if in later kernels tty->dev is dereferenced by some
> > codes? Is it better to apply this check for this reason?
>
> So for the above reason, no.
>
> Johan
next prev parent reply other threads:[~2019-05-22 11:25 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 1:40 [PATCH] tty_io: Fix a missing-check bug in drivers/tty/tty_io.c Gen Zhang
2019-05-22 4:25 ` Jiri Slaby
2019-05-22 8:06 ` Gen Zhang
2019-05-22 8:15 ` Jiri Slaby
2019-05-22 10:29 ` Johan Hovold
2019-05-22 10:32 ` Jiri Slaby
2019-05-22 11:13 ` Gen Zhang
2019-05-22 11:19 ` Johan Hovold
2019-05-22 11:24 ` Gen Zhang [this message]
2019-05-22 11:18 ` Gen Zhang
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