[PATCH] fs, security: Fix file_set_fowner LSM hook inconsistencies

[kernel test robot]

Hi Mickaël,

kernel test robot noticed the following build warnings:

[auto build test WARNING on pcmoore-selinux/next]
[also build test WARNING on linus/master v6.11-rc3 next-20240812]
[cannot apply to brauner-vfs/vfs.all]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Micka-l-Sala-n/fs-security-Fix-file_set_fowner-LSM-hook-inconsistencies/20240813-004648
base:   https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux.git next
patch link:    https://lore.kernel.org/r/20240812144936.1616628-1-mic%40digikod.net
patch subject: [PATCH] fs,security: Fix file_set_fowner LSM hook inconsistencies
config: m68k-allmodconfig (https://download.01.org/0day-ci/archive/20240813/202408130946.6oMWnayg-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 14.1.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240813/202408130946.6oMWnayg-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp at intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202408130946.6oMWnayg-lkp@intel.com/

All warnings (new ones prefixed by >>):

   security/smack/smack_lsm.c: In function 'smack_file_send_sigiotask':
>> security/smack/smack_lsm.c:1913:22: warning: variable 'file' set but not used [-Wunused-but-set-variable]
    1913 |         struct file *file;
         |                      ^~~~


vim +/file +1913 security/smack/smack_lsm.c

7898e1f8e9eb1b Casey Schaufler 2011-01-17  1895  
e114e473771c84 Casey Schaufler 2008-02-04  1896  /**
e114e473771c84 Casey Schaufler 2008-02-04  1897   * smack_file_send_sigiotask - Smack on sigio
e114e473771c84 Casey Schaufler 2008-02-04  1898   * @tsk: The target task
e114e473771c84 Casey Schaufler 2008-02-04  1899   * @fown: the object the signal come from
e114e473771c84 Casey Schaufler 2008-02-04  1900   * @signum: unused
e114e473771c84 Casey Schaufler 2008-02-04  1901   *
e114e473771c84 Casey Schaufler 2008-02-04  1902   * Allow a privileged task to get signals even if it shouldn't
e114e473771c84 Casey Schaufler 2008-02-04  1903   *
e114e473771c84 Casey Schaufler 2008-02-04  1904   * Returns 0 if a subject with the object's smack could
e114e473771c84 Casey Schaufler 2008-02-04  1905   * write to the task, an error code otherwise.
e114e473771c84 Casey Schaufler 2008-02-04  1906   */
e114e473771c84 Casey Schaufler 2008-02-04  1907  static int smack_file_send_sigiotask(struct task_struct *tsk,
e114e473771c84 Casey Schaufler 2008-02-04  1908  				     struct fown_struct *fown, int signum)
e114e473771c84 Casey Schaufler 2008-02-04  1909  {
2f823ff8bec03a Casey Schaufler 2013-05-22  1910  	struct smack_known *skp;
b17103a8b8ae9c Casey Schaufler 2018-11-09  1911  	struct smack_known *tkp = smk_of_task(smack_cred(tsk->cred));
dcb569cf6ac99c Casey Schaufler 2018-09-18  1912  	const struct cred *tcred;
e114e473771c84 Casey Schaufler 2008-02-04 @1913  	struct file *file;
e114e473771c84 Casey Schaufler 2008-02-04  1914  	int rc;
ecfcc53fef3c35 Etienne Basset  2009-04-08  1915  	struct smk_audit_info ad;
e114e473771c84 Casey Schaufler 2008-02-04  1916  
e114e473771c84 Casey Schaufler 2008-02-04  1917  	/*
e114e473771c84 Casey Schaufler 2008-02-04  1918  	 * struct fown_struct is never outside the context of a struct file
e114e473771c84 Casey Schaufler 2008-02-04  1919  	 */
e114e473771c84 Casey Schaufler 2008-02-04  1920  	file = container_of(fown, struct file, f_owner);
7898e1f8e9eb1b Casey Schaufler 2011-01-17  1921  
ecfcc53fef3c35 Etienne Basset  2009-04-08  1922  	/* we don't log here as rc can be overriden */
32192c8e14ea34 Mickaël Salaün  2024-08-12  1923  	skp = smk_of_task(smack_cred(rcu_dereference(fown->cred)));
c60b906673eebb Casey Schaufler 2016-08-30  1924  	rc = smk_access(skp, tkp, MAY_DELIVER, NULL);
c60b906673eebb Casey Schaufler 2016-08-30  1925  	rc = smk_bu_note("sigiotask", skp, tkp, MAY_DELIVER, rc);
dcb569cf6ac99c Casey Schaufler 2018-09-18  1926  
dcb569cf6ac99c Casey Schaufler 2018-09-18  1927  	rcu_read_lock();
dcb569cf6ac99c Casey Schaufler 2018-09-18  1928  	tcred = __task_cred(tsk);
dcb569cf6ac99c Casey Schaufler 2018-09-18  1929  	if (rc != 0 && smack_privileged_cred(CAP_MAC_OVERRIDE, tcred))
ecfcc53fef3c35 Etienne Basset  2009-04-08  1930  		rc = 0;
dcb569cf6ac99c Casey Schaufler 2018-09-18  1931  	rcu_read_unlock();
ecfcc53fef3c35 Etienne Basset  2009-04-08  1932  
ecfcc53fef3c35 Etienne Basset  2009-04-08  1933  	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
ecfcc53fef3c35 Etienne Basset  2009-04-08  1934  	smk_ad_setfield_u_tsk(&ad, tsk);
c60b906673eebb Casey Schaufler 2016-08-30  1935  	smack_log(skp->smk_known, tkp->smk_known, MAY_DELIVER, rc, &ad);
e114e473771c84 Casey Schaufler 2008-02-04  1936  	return rc;
e114e473771c84 Casey Schaufler 2008-02-04  1937  }
e114e473771c84 Casey Schaufler 2008-02-04  1938  

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