From: Li Zhong <floridsleeves@gmail.com>
To: "Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jirislaby@kernel.org>
Subject: Re: [PATCH v2] drivers/tty/serial: check the return value of uart_port_check()
Date: Sat, 3 Sep 2022 16:14:59 -0700 [thread overview]
Message-ID: <CAMEuxRpm5xNm2kEnhCSimoaCE3zSxbyoo7xUxNg74QrL7F6YUg@mail.gmail.com> (raw)
In-Reply-To: <40e16474-99d2-2359-a545-4a437f555ec1@linux.intel.com>
On Tue, Aug 30, 2022 at 12:20 AM Ilpo Järvinen
<ilpo.jarvinen@linux.intel.com> wrote:
>
> On Mon, 29 Aug 2022, Li Zhong wrote:
>
> > On Mon, Aug 29, 2022 at 12:09 AM Ilpo Järvinen
> > <ilpo.jarvinen@linux.intel.com> wrote:
> > >
> > > On Sun, 28 Aug 2022, Li Zhong wrote:
> > >
> > > > On Fri, Aug 26, 2022 at 9:01 AM Andy Shevchenko
> > > > <andy.shevchenko@gmail.com> wrote:
> > > > >
> > > > > On Fri, Aug 26, 2022 at 11:38 AM Li Zhong <floridsleeves@gmail.com> wrote:
> > > > > >
> > > > > > uart_port_check() will return NULL pointer when state->uart_port is
> > > > > > NULL. Check the return value before dereference it to avoid
> > > > > > null-pointer-dereference error.
> > > > >
> > > > > Have you taken the locking into consideration?
> > > > > If no, please do, if yes, expand your commit message to explain why
> > > > > the current locking scheme doesn't prevent an error from happening.
> > > > >
> > > >
> > > > The locking is taken into consideration but these three checks do not need to
> > > > unlock in error-handling because unlock() will be called in the callers. Will
> > > > add the comment in v2 patch.
> > >
> > > I think he meant you should indicate why the current locking doesn't cover
> > > the case you're fixing, not whether this function should call unlock() or
> > > not.
> > >
> >
> > Thanks for clarifications. The locking does not guarantee the return value of
> > uart_port_check() is not NULL.
>
> Please put such explanation into the commit message like Andy was asking,
> thank you.
>
Thanks! I'll add this into the v3 patch.
> And make sure you properly mention what has changed for any new version
> of any patch you send so that Greg don't need to auto-mail you about it
> (and end up ignoring your patch).
>
I'll mention this in the commit message of new patch.
> > Actually in line 773 of this file
> > (drivers/tty/serial/serial_core.c), uart_port_check() is also called in
> > critical section but still there is check on whether the return value is NULL.
>
> Existance of such a check elsewhere alone isn't enough to guarantee that
> the check is necessary (and not even that the check in that other place
> would be necessary). You need a deeper analysis than that. I'm not
> claiming its either way here, just pointing out to the direction/details
> you should consider while writing the analysis of the problem.
>
Thanks for the suggestions. We will try consider more factor into our analysis
tools to reduce false postives.
>
> --
> i.
prev parent reply other threads:[~2022-09-03 23:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-26 8:36 [PATCH v2] drivers/tty/serial: check the return value of uart_port_check() Li Zhong
2022-08-26 16:01 ` Andy Shevchenko
2022-08-28 19:57 ` Li Zhong
2022-08-29 7:09 ` Ilpo Järvinen
2022-08-30 6:59 ` Li Zhong
2022-08-30 7:20 ` Ilpo Järvinen
2022-09-03 23:14 ` Li Zhong [this message]
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