Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220826083612.1699194-1-floridsleeves@gmail.com>
 <CAHp75VcdqL4wYnhEi8LrxqJktA2uDzP3a6-08suJRghX=1UZsg@mail.gmail.com>
 <CAMEuxRqBEMdva3qEphvuYkFLpRjp=xg7vpqQT1oqb2AgkkG2+w@mail.gmail.com> <2033d06d-10a4-5a57-d650-7541c39990ee@linux.intel.com>
In-Reply-To: <2033d06d-10a4-5a57-d650-7541c39990ee@linux.intel.com>
From:   Li Zhong <floridsleeves@gmail.com>
Date:   Mon, 29 Aug 2022 23:59:45 -0700
Message-ID: <CAMEuxRq6wn+wakYHGtnS_vSgpcw6aNOir=KyXWb12vPrOr76pA@mail.gmail.com>
Subject: Re: [PATCH v2] drivers/tty/serial: check the return value of uart_port_check()
To:     =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= <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>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Mon, Aug 29, 2022 at 12:09 AM Ilpo J=C3=A4rvinen
<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> w=
rote:
> > > >
> > > > 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 n=
eed 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 cove=
r
> 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. 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 NU=
LL.

> --
>  i.
>