Re: [PATCH V2] SELinux: Check correct permissions for FS_IOC32_*

[Stephen Smalley]

On Mon, Sep 11, 2023 at 9:19 AM Stephen Smalley
<stephen.smalley.work@xxxxxxxxx> wrote:
>
> On Fri, Sep 8, 2023 at 6:54 PM kernel test robot <lkp@xxxxxxxxx> wrote:
> >
> > Hi Alfred,
> >
> > kernel test robot noticed the following build errors:
> >
> > [auto build test ERROR on 50a510a78287c15cee644f345ef8bac8977986a7]
> >
> > url:    https://github.com/intel-lab-lkp/linux/commits/Alfred-Piccioni/SELinux-Check-correct-permissions-for-FS_IOC32_/20230906-200131
> > base:   50a510a78287c15cee644f345ef8bac8977986a7
> > patch link:    https://lore.kernel.org/r/20230906115928.3749928-1-alpic%40google.com
> > patch subject: [PATCH V2] SELinux: Check correct permissions for FS_IOC32_*
> > config: i386-debian-10.3 (https://download.01.org/0day-ci/archive/20230909/202309090600.NSyo7d2q-lkp@xxxxxxxxx/config)
> > compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
> > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230909/202309090600.NSyo7d2q-lkp@xxxxxxxxx/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@xxxxxxxxx>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202309090600.NSyo7d2q-lkp@xxxxxxxxx/
> >
> > All errors (new ones prefixed by >>):
> >
> >    security/selinux/hooks.c: In function 'selinux_file_ioctl':
> > >> security/selinux/hooks.c:3647:9: error: duplicate case value
> >     3647 |         case FS_IOC32_GETFLAGS:
> >          |         ^~~~
> >    security/selinux/hooks.c:3645:9: note: previously used here
> >     3645 |         case FS_IOC_GETFLAGS:
> >          |         ^~~~
> >    security/selinux/hooks.c:3648:9: error: duplicate case value
> >     3648 |         case FS_IOC32_GETVERSION:
> >          |         ^~~~
> >    security/selinux/hooks.c:3646:9: note: previously used here
> >     3646 |         case FS_IOC_GETVERSION:
> >          |         ^~~~
> >    security/selinux/hooks.c:3654:9: error: duplicate case value
> >     3654 |         case FS_IOC32_SETFLAGS:
> >          |         ^~~~
> >    security/selinux/hooks.c:3652:9: note: previously used here
> >     3652 |         case FS_IOC_SETFLAGS:
> >          |         ^~~~
> >    security/selinux/hooks.c:3655:9: error: duplicate case value
> >     3655 |         case FS_IOC32_SETVERSION:
> >          |         ^~~~
> >    security/selinux/hooks.c:3653:9: note: previously used here
> >     3653 |         case FS_IOC_SETVERSION:
> >          |         ^~~~
>
> Not sure of the right way to fix this while addressing the original
> issue that this patch was intended to fix. Looking in fs/ioctl.c, I
> see that the some FS_IOC32 values are remapped to the corresponding
> FS_IOC values by the compat ioctl syscall entrypoint. Also notice this
> comment there:
>
>         /* RED-PEN how should LSM module know it's handling 32bit? */
>         error = security_file_ioctl(f.file, cmd, arg);
>         if (error)
>                 goto out;
>
> So perhaps this is a defect in LSM that needs to be addressed?

Note btw that some of the 32-bit ioctl commands are only handled in
the fs-specific compat_ioctl routines, e.g. ext4_compat_ioctl()
handles EXT4_IOC32_GETVERSION == FS_IOC32_GETVERSION and ditto for
_SETVERSION.

>
>
> >
> >
> > vim +3647 security/selinux/hooks.c
> >
> >   3634
> >   3635  static int selinux_file_ioctl(struct file *file, unsigned int cmd,
> >   3636                                unsigned long arg)
> >   3637  {
> >   3638          const struct cred *cred = current_cred();
> >   3639          int error = 0;
> >   3640
> >   3641          switch (cmd) {
> >   3642          case FIONREAD:
> >   3643          case FIBMAP:
> >   3644          case FIGETBSZ:
> >   3645          case FS_IOC_GETFLAGS:
> >   3646          case FS_IOC_GETVERSION:
> > > 3647          case FS_IOC32_GETFLAGS:
> >   3648          case FS_IOC32_GETVERSION:
> >   3649                  error = file_has_perm(cred, file, FILE__GETATTR);
> >   3650                  break;
> >   3651
> >   3652          case FS_IOC_SETFLAGS:
> >   3653          case FS_IOC_SETVERSION:
> >   3654          case FS_IOC32_SETFLAGS:
> >   3655          case FS_IOC32_SETVERSION:
> >   3656                  error = file_has_perm(cred, file, FILE__SETATTR);
> >   3657                  break;
> >   3658
> >   3659          /* sys_ioctl() checks */
> >   3660          case FIONBIO:
> >   3661          case FIOASYNC:
> >   3662                  error = file_has_perm(cred, file, 0);
> >   3663                  break;
> >   3664
> >   3665          case KDSKBENT:
> >   3666          case KDSKBSENT:
> >   3667                  error = cred_has_capability(cred, CAP_SYS_TTY_CONFIG,
> >   3668                                              CAP_OPT_NONE, true);
> >   3669                  break;
> >   3670
> >   3671          case FIOCLEX:
> >   3672          case FIONCLEX:
> >   3673                  if (!selinux_policycap_ioctl_skip_cloexec())
> >   3674                          error = ioctl_has_perm(cred, file, FILE__IOCTL, (u16) cmd);
> >   3675                  break;
> >   3676
> >   3677          /* default case assumes that the command will go
> >   3678           * to the file's ioctl() function.
> >   3679           */
> >   3680          default:
> >   3681                  error = ioctl_has_perm(cred, file, FILE__IOCTL, (u16) cmd);
> >   3682          }
> >   3683          return error;
> >   3684  }
> >   3685