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: <20230417165246.467723-1-zyytlz.wz@163.com> <cabf202f-a58e-4637-9d55-b0382360c27e@kili.mountain>
 <CAJedcCzuPkHHy=uxtyuRT-Qvs56ooZ_irL89KdPq99XxgxfLBw@mail.gmail.com> <daacdf0d-605a-4a3b-a599-3a15857ec224@kili.mountain>
In-Reply-To: <daacdf0d-605a-4a3b-a599-3a15857ec224@kili.mountain>
From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Fri, 5 May 2023 15:35:46 +0800
Message-ID: <CAJedcCwwOkTcKvJ7PXa+s=46MnaVRCRK8HSehoj2bziLUhaD5w@mail.gmail.com>
Subject: Re: [PATCH] misc: hpilo: Fix use after free bug in ilo_remove due to
 race condition with ilo_open
To:     Dan Carpenter <dan.carpenter@linaro.org>
Cc:     oe-kbuild@lists.linux.dev, Zheng Wang <zyytlz.wz@163.com>,
        matt.hsiao@hpe.com, lkp@intel.com, oe-kbuild-all@lists.linux.dev,
        arnd@arndb.de, gregkh@linuxfoundation.org,
        linux-kernel@vger.kernel.org, 1395428693sheep@gmail.com,
        alex000young@gmail.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Dan Carpenter <dan.carpenter@linaro.org> =E4=BA=8E2023=E5=B9=B45=E6=9C=885=
=E6=97=A5=E5=91=A8=E4=BA=94 15:31=E5=86=99=E9=81=93=EF=BC=9A
>
> On Fri, May 05, 2023 at 12:01:17PM +0800, Zheng Hacker wrote:
> > Dear Dan,
> >
> > Thanks for your reply. I'm not so familiar with the code here. Is the
> > warning says we should check ilo_hw to see if it's not NULL?
> >
>
> Just delete the NULL check.  It's impossible.
>

Thanks for your explaination.

Best regards,
Zheng

> regards,
> dan carpenter
>
> > Best regards,
> > Zheng
> >
> > Dan Carpenter <dan.carpenter@linaro.org> =E4=BA=8E2023=E5=B9=B45=E6=9C=
=882=E6=97=A5=E5=91=A8=E4=BA=8C 19:46=E5=86=99=E9=81=93=EF=BC=9A
> > >
> > > Hi Zheng,
> > >
> > > kernel test robot noticed the following build warnings:
> > >
> > > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> > >
> > > url:    https://github.com/intel-lab-lkp/linux/commits/Zheng-Wang/mis=
c-hpilo-Fix-use-after-free-bug-in-ilo_remove-due-to-race-condition-with-ilo=
_open/20230418-005502
> > > base:   char-misc/char-misc-testing
> > > patch link:    https://lore.kernel.org/r/20230417165246.467723-1-zyyt=
lz.wz%40163.com
> > > patch subject: [PATCH] misc: hpilo: Fix use after free bug in ilo_rem=
ove due  to race condition with ilo_open
> > > config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive=
/20230430/202304300909.ALHN6Vry-lkp@intel.com/config)
> > > compiler: gcc-11 (Debian 11.3.0-12) 11.3.0
> > >
> > > If you fix the issue, kindly add following tag where applicable
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Reported-by: Dan Carpenter <error27@gmail.com>
> > > | Link: https://lore.kernel.org/r/202304300909.ALHN6Vry-lkp@intel.com=
/
> > >
> > > smatch warnings:
> > > drivers/misc/hpilo.c:755 ilo_delete() warn: can 'ilo_hw' even be NULL=
?
> > >
> > > vim +/ilo_hw +755 drivers/misc/hpilo.c
> > >
> > > 13a22f45e6cb1e Zheng Wang      2023-04-18  749  static void ilo_delet=
e(struct kref *kref)
> > > 13a22f45e6cb1e Zheng Wang      2023-04-18  750  {
> > > 13a22f45e6cb1e Zheng Wang      2023-04-18  751          int i, minor;
> > > 13a22f45e6cb1e Zheng Wang      2023-04-18  752          struct ilo_hw=
info *ilo_hw =3D container_of(kref, struct ilo_hwinfo, refcnt);
> > > 13a22f45e6cb1e Zheng Wang      2023-04-18  753          struct pci_de=
v *pdev =3D ilo_hw->ilo_dev;
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  754
> > > ebf1b764aa5cb3 Mark Rusk       2012-11-06 @755          if (!ilo_hw)
> > >                                                             ^^^^^^^
> > >
> > > ->refcnt member isn't the first struct member so this NULL check
> > > doesn't make sense.  Generally checking container_of() is ugly.  Some
> > > people do it and add BUILD_BUG_ON() to ensure that they're checking t=
he
> > > first struct member but really it's best to avoid that if possible.
> > >
> > > ebf1b764aa5cb3 Mark Rusk       2012-11-06  756                  retur=
n;
> > > ebf1b764aa5cb3 Mark Rusk       2012-11-06  757
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  758          clear_device(=
ilo_hw);
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  759
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  760          minor =3D MIN=
OR(ilo_hw->cdev.dev);
> > > 98dcd59dd063dd Camuso, Tony    2012-06-10  761          for (i =3D mi=
nor; i < minor + max_ccb; i++)
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  762                  devic=
e_destroy(ilo_class, MKDEV(ilo_major, i));
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  763
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  764          cdev_del(&ilo=
_hw->cdev);
> > > 9f7048412163d8 David Altobelli 2009-08-17  765          ilo_disable_i=
nterrupts(ilo_hw);
> > > 9f7048412163d8 David Altobelli 2009-08-17  766          free_irq(pdev=
->irq, ilo_hw);
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  767          ilo_unmap_dev=
ice(pdev, ilo_hw);
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  768          pci_release_r=
egions(pdev);
> > > bcdee04ea7ae04 Jiri Slaby      2012-09-13  769          /*
> > > bcdee04ea7ae04 Jiri Slaby      2012-09-13  770           * pci_disabl=
e_device(pdev) used to be here. But this PCI device has
> > > bcdee04ea7ae04 Jiri Slaby      2012-09-13  771           * two functi=
ons with interrupt lines connected to a single pin. The
> > > bcdee04ea7ae04 Jiri Slaby      2012-09-13  772           * other one =
is a USB host controller. So when we disable the PIN here
> > > bcdee04ea7ae04 Jiri Slaby      2012-09-13  773           * e.g. by rm=
mod hpilo, the controller stops working. It is because
> > > bcdee04ea7ae04 Jiri Slaby      2012-09-13  774           * the interr=
upt link is disabled in ACPI since it is not refcounted
> > > bcdee04ea7ae04 Jiri Slaby      2012-09-13  775           * yet. See a=
cpi_pci_link_free_irq called from acpi_pci_irq_disable.
> > > bcdee04ea7ae04 Jiri Slaby      2012-09-13  776           */
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  777          kfree(ilo_hw)=
;
> > > 98dcd59dd063dd Camuso, Tony    2012-06-10  778          ilo_hwdev[(mi=
nor / max_ccb)] =3D 0;
> > > 89bcb05d9bbf8b David Altobelli 2008-07-02  779  }
> > >
> > > --
> > > 0-DAY CI Kernel Test Service
> > > https://github.com/intel/lkp-tests
> > >