Re: [PATCH] misc: hpilo: Fix use after free bug in ilo_remove due to race condition with ilo_open

[Zheng Hacker]

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?

Best regards,
Zheng

Dan Carpenter <dan.carpenter@xxxxxxxxxx> 于2023年5月2日周二 19:46写道：
>
> 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/misc-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-zyytlz.wz%40163.com
> patch subject: [PATCH] misc: hpilo: Fix use after free bug in ilo_remove due  to race condition with ilo_open
> config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20230430/202304300909.ALHN6Vry-lkp@xxxxxxxxx/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@xxxxxxxxx>
> | Reported-by: Dan Carpenter <error27@xxxxxxxxx>
> | Link: https://lore.kernel.org/r/202304300909.ALHN6Vry-lkp@xxxxxxxxx/
>
> 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_delete(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_hwinfo *ilo_hw = container_of(kref, struct ilo_hwinfo, refcnt);
> 13a22f45e6cb1e Zheng Wang      2023-04-18  753          struct pci_dev *pdev = 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 the
> first struct member but really it's best to avoid that if possible.
>
> ebf1b764aa5cb3 Mark Rusk       2012-11-06  756                  return;
> 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 = MINOR(ilo_hw->cdev.dev);
> 98dcd59dd063dd Camuso, Tony    2012-06-10  761          for (i = minor; i < minor + max_ccb; i++)
> 89bcb05d9bbf8b David Altobelli 2008-07-02  762                  device_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_interrupts(ilo_hw);
> 9f7048412163d8 David Altobelli 2009-08-17  766          free_irq(pdev->irq, ilo_hw);
> 89bcb05d9bbf8b David Altobelli 2008-07-02  767          ilo_unmap_device(pdev, ilo_hw);
> 89bcb05d9bbf8b David Altobelli 2008-07-02  768          pci_release_regions(pdev);
> bcdee04ea7ae04 Jiri Slaby      2012-09-13  769          /*
> bcdee04ea7ae04 Jiri Slaby      2012-09-13  770           * pci_disable_device(pdev) used to be here. But this PCI device has
> bcdee04ea7ae04 Jiri Slaby      2012-09-13  771           * two functions 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 rmmod hpilo, the controller stops working. It is because
> bcdee04ea7ae04 Jiri Slaby      2012-09-13  774           * the interrupt link is disabled in ACPI since it is not refcounted
> bcdee04ea7ae04 Jiri Slaby      2012-09-13  775           * yet. See acpi_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[(minor / max_ccb)] = 0;
> 89bcb05d9bbf8b David Altobelli 2008-07-02  779  }
>
> --
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> https://github.com/intel/lkp-tests
>