From: Johan Hovold <johan@kernel.org>
To: Gen Zhang <blackgod016574@gmail.com>
Cc: Johan Hovold <johan@kernel.org>, 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 13:19:49 +0200 [thread overview]
Message-ID: <20190522111949.GB568@localhost> (raw)
In-Reply-To: <20190522111354.GA5849@zhanggen-UX430UQ>
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.
> 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 11:19 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 [this message]
2019-05-22 11:24 ` Gen Zhang
2019-05-22 11:18 ` Gen Zhang
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