security/selinux/hooks.c | 4 ++++ 1 file changed, 4 insertions(+)
Some ioctl commands do not require ioctl permission, but are routed to
other permissions such as FILE_GETATTR or FILE_SETATTR. This routing is
done by comparing the ioctl cmd to a set of 64-bit flags (FS_IOC_*).
However, if a 32-bit process is running on a 64-bit kernel, it emits
32-bit flags (FS_IOC32_*) for certain ioctl operations. These flags are
being checked erroneously, which leads to these ioctl operations being
routed to the ioctl permission, rather than the correct file permissions.
Two possible solutions exist:
- Trim parameter "cmd" to a u16 so that only the last two bytes are
checked in the case statement.
- Explicitly add the FS_IOC32_* codes to the case statement.
Solution 2 was chosen because it is a minimal explicit change. Solution
1 is a more elegant change, but is less explicit, as the switch
statement appears to only check the FS_IOC_* codes upon first reading.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"")
Signed-off-by: Alfred Piccioni <alpic@google.com>
Cc: stable@vger.kernel.org
---
V1->V2: Cleaned up some typos and added tag for -stable tree inclusion.
security/selinux/hooks.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index d06e350fedee..bba83f437a1d 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3644,11 +3644,15 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd,
case FIGETBSZ:
case FS_IOC_GETFLAGS:
case FS_IOC_GETVERSION:
+ case FS_IOC32_GETFLAGS:
+ case FS_IOC32_GETVERSION:
error = file_has_perm(cred, file, FILE__GETATTR);
break;
case FS_IOC_SETFLAGS:
case FS_IOC_SETVERSION:
+ case FS_IOC32_SETFLAGS:
+ case FS_IOC32_SETVERSION:
error = file_has_perm(cred, file, FILE__SETATTR);
break;
base-commit: 50a510a78287c15cee644f345ef8bac8977986a7
--
2.42.0.283.g2d96d420d3-googHi 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@intel.com/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@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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202309090600.NSyo7d2q-lkp@intel.com/
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:
| ^~~~
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
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
On Fri, Sep 8, 2023 at 6:54 PM kernel test robot <lkp@intel.com> 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@intel.com/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@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@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202309090600.NSyo7d2q-lkp@intel.com/
>
> 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?
>
>
> 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
On Mon, Sep 11, 2023 at 9:19 AM Stephen Smalley <stephen.smalley.work@gmail.com> wrote: > On Fri, Sep 8, 2023 at 6:54 PM kernel test robot <lkp@intel.com> 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@intel.com/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@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@intel.com> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202309090600.NSyo7d2q-lkp@intel.com/ > > > > 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; What is both interesting and scary is that the "RED-PEN" comment seems to go back at least as far as git, which is a lifetime these days. This has been broken for a while. > So perhaps this is a defect in LSM that needs to be addressed? I think so. I would suggest a new security_file_ioctl_compat() hook as I often worry that flags are too easy to misuse whereas a separate hook, especially one with "_compat" at the end, are a bit more clear. The good news is that of the three LSMs that have file_ioctl hook implementations it looks like only SELinux will need a dedicated compat hook implementation (*maybe* TOMOYO, but I think it should be okay reusing the existing tomoyo_file_ioctl() implementation). -- paul-moore.com
On Mon, Sep 11, 2023 at 9:19 AM Stephen Smalley
<stephen.smalley.work@gmail.com> wrote:
>
> On Fri, Sep 8, 2023 at 6:54 PM kernel test robot <lkp@intel.com> 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@intel.com/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@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@intel.com>
> > | Closes: https://lore.kernel.org/oe-kbuild-all/202309090600.NSyo7d2q-lkp@intel.com/
> >
> > 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
On Mon, Sep 11, 2023 at 3:49 PM Stephen Smalley
<stephen.smalley.work@gmail.com> wrote:
>
> On Mon, Sep 11, 2023 at 9:19 AM Stephen Smalley
> <stephen.smalley.work@gmail.com> wrote:
> >
> > On Fri, Sep 8, 2023 at 6:54 PM kernel test robot <lkp@intel.com> 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@intel.com/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@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@intel.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202309090600.NSyo7d2q-lkp@intel.com/
> > >
> > > 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
Hey Stephen,
Thanks for looking into it a bit deeper! This seems a bit of a pickle.
I can think of a few somewhat hacky ways to fix this.
I can just set the flags to check `if FS_IOC32_*; set FS_IOC_*;`,
which is the quickest but kinda hacky.
I can go with the other plan of dropping the irrelevant bytes from the
cmd code, so all codes will be read as u16. This effectively does the
same thing, but may be unclear.
I can also look into whether this can be solved at the LSM or a higher
level. Perhaps the filesystems setting `if FS_IOC32_*; set FS_IOC_*;`
is a hint that something else interesting is going wrong.
I'll spend a little time thinking and investigating and get back with
a more concrete solution. I'll also need to do a bit more robust
testing; it built on my machine!
Thanks!
On Tue, Sep 12, 2023 at 5:00 AM Alfred Piccioni <alpic@google.com> wrote:
>
> On Mon, Sep 11, 2023 at 3:49 PM Stephen Smalley
> <stephen.smalley.work@gmail.com> wrote:
> >
> > On Mon, Sep 11, 2023 at 9:19 AM Stephen Smalley
> > <stephen.smalley.work@gmail.com> wrote:
> > >
> > > On Fri, Sep 8, 2023 at 6:54 PM kernel test robot <lkp@intel.com> 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@intel.com/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@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@intel.com>
> > > > | Closes: https://lore.kernel.org/oe-kbuild-all/202309090600.NSyo7d2q-lkp@intel.com/
> > > >
> > > > 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
>
> Hey Stephen,
>
> Thanks for looking into it a bit deeper! This seems a bit of a pickle.
> I can think of a few somewhat hacky ways to fix this.
>
> I can just set the flags to check `if FS_IOC32_*; set FS_IOC_*;`,
> which is the quickest but kinda hacky.
>
> I can go with the other plan of dropping the irrelevant bytes from the
> cmd code, so all codes will be read as u16. This effectively does the
> same thing, but may be unclear.
>
> I can also look into whether this can be solved at the LSM or a higher
> level. Perhaps the filesystems setting `if FS_IOC32_*; set FS_IOC_*;`
> is a hint that something else interesting is going wrong.
>
> I'll spend a little time thinking and investigating and get back with
> a more concrete solution. I'll also need to do a bit more robust
> testing; it built on my machine!
Likewise for me; I don't generally try building for 32-bit systems.
Remapping FS_IOC32_* to FS_IOC_* in selinux_file_ioctl() seems
reasonable to me although optimally that would be conditional on
whether selinux_file_ioctl() is being called from the compat ioctl
syscall (e.g. adding a flag to the LSM hook to indicate this or using
a separate hook for it). Otherwise we might misinterpret some other
ioctl on 64-bit.
If we didn't have compatibility requirements, it would be tempting to
just get rid of all the special case ioctl command handling in
selinux_file_ioctl() and let ioctl_has_perm() handle them all with the
extended ioctl permissions support. But that would require a SELinux
policy cap to switch it on conditionally for compatibility at least
and not sure anyone is willing to refactor their policies accordingly.
>
> Thanks!
On Tue, Sep 12, 2023 at 08:00:12AM -0400, Stephen Smalley wrote:
> On Tue, Sep 12, 2023 at 5:00 AM Alfred Piccioni <alpic@google.com> wrote:
> >
> > On Mon, Sep 11, 2023 at 3:49 PM Stephen Smalley
> > <stephen.smalley.work@gmail.com> wrote:
> > >
> > > On Mon, Sep 11, 2023 at 9:19 AM Stephen Smalley
> > > <stephen.smalley.work@gmail.com> wrote:
> > > >
> > > > On Fri, Sep 8, 2023 at 6:54 PM kernel test robot <lkp@intel.com> 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@intel.com/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@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@intel.com>
> > > > > | Closes: https://lore.kernel.org/oe-kbuild-all/202309090600.NSyo7d2q-lkp@intel.com/
> > > > >
> > > > > 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
> >
> > Hey Stephen,
> >
> > Thanks for looking into it a bit deeper! This seems a bit of a pickle.
> > I can think of a few somewhat hacky ways to fix this.
> >
> > I can just set the flags to check `if FS_IOC32_*; set FS_IOC_*;`,
> > which is the quickest but kinda hacky.
> >
> > I can go with the other plan of dropping the irrelevant bytes from the
> > cmd code, so all codes will be read as u16. This effectively does the
> > same thing, but may be unclear.
> >
> > I can also look into whether this can be solved at the LSM or a higher
> > level. Perhaps the filesystems setting `if FS_IOC32_*; set FS_IOC_*;`
> > is a hint that something else interesting is going wrong.
> >
> > I'll spend a little time thinking and investigating and get back with
> > a more concrete solution. I'll also need to do a bit more robust
> > testing; it built on my machine!
>
> Likewise for me; I don't generally try building for 32-bit systems.
> Remapping FS_IOC32_* to FS_IOC_* in selinux_file_ioctl() seems
> reasonable to me although optimally that would be conditional on
> whether selinux_file_ioctl() is being called from the compat ioctl
> syscall (e.g. adding a flag to the LSM hook to indicate this or using
> a separate hook for it). Otherwise we might misinterpret some other
> ioctl on 64-bit.
I think adding a boolean argument to the LSM hook makes sense. LSMs
might decide to handle it or not, at their own pace.
>
> If we didn't have compatibility requirements, it would be tempting to
> just get rid of all the special case ioctl command handling in
> selinux_file_ioctl() and let ioctl_has_perm() handle them all with the
> extended ioctl permissions support. But that would require a SELinux
> policy cap to switch it on conditionally for compatibility at least
> and not sure anyone is willing to refactor their policies accordingly.
On Wed, Sep 6, 2023 at 7:59 AM Alfred Piccioni <alpic@google.com> wrote:
>
> Some ioctl commands do not require ioctl permission, but are routed to
> other permissions such as FILE_GETATTR or FILE_SETATTR. This routing is
> done by comparing the ioctl cmd to a set of 64-bit flags (FS_IOC_*).
>
> However, if a 32-bit process is running on a 64-bit kernel, it emits
> 32-bit flags (FS_IOC32_*) for certain ioctl operations. These flags are
> being checked erroneously, which leads to these ioctl operations being
> routed to the ioctl permission, rather than the correct file permissions.
>
> Two possible solutions exist:
>
> - Trim parameter "cmd" to a u16 so that only the last two bytes are
> checked in the case statement.
>
> - Explicitly add the FS_IOC32_* codes to the case statement.
>
> Solution 2 was chosen because it is a minimal explicit change. Solution
> 1 is a more elegant change, but is less explicit, as the switch
> statement appears to only check the FS_IOC_* codes upon first reading.
>
> Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"")
> Signed-off-by: Alfred Piccioni <alpic@google.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Stephen Smalley <stephen.smalley.work@gmail.com>
> ---
> V1->V2: Cleaned up some typos and added tag for -stable tree inclusion.
>
> security/selinux/hooks.c | 4 ++++
> 1 file changed, 4 insertions(+)
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