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

[Dan Carpenter]

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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