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 emmits 32-bit flags (FS_IOC32_*) for certain ioctl operations. These flags are being checked erroneoulsy, 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.
- Explicitily 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 --- 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
Hi,
Thanks for your patch.
FYI: kernel test robot notices the stable kernel rule is not satisfied.
The check is based on https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html/#opt...
Rule: add the tag "Cc: stable@vger.kernel.org" in the sign-off area to have the patch automatically included in the stable tree. Subject: [PATCH] SELinux: Check correct permissions for FS_IOC32_* Link: https://lore.kernel.org/stable/20230906102557.3432236-1-alpic%40google.com
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
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(+)
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... 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@i...) 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@i...)
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
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... 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@i...) 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@i...)
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... 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@i...) 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@i...)
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... 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@i...) 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@i...)
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... 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@i...) 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@i...)
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... 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@i...) 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@i...)
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 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... 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@i...) 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@i...)
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).
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 emmits 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.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that replaces security_file_ioctl if the CONFIG_COMPAT flag is on. All current LSMs have been changed to hook into the compat flag.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"") Signed-off-by: Alfred Piccioni alpic@google.com Cc: stable@vger.kernel.org --- fs/ioctl.c | 3 +-- fs/overlayfs/inode.c | 4 ++++ include/linux/lsm_hook_defs.h | 2 ++ include/linux/security.h | 7 +++++++ security/security.c | 17 +++++++++++++++++ security/selinux/hooks.c | 26 ++++++++++++++++++++++++++ security/smack/smack_lsm.c | 1 + security/tomoyo/tomoyo.c | 1 + 8 files changed, 59 insertions(+), 2 deletions(-)
diff --git a/fs/ioctl.c b/fs/ioctl.c index f5fd99d6b0d4..76cf22ac97d7 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -920,8 +920,7 @@ COMPAT_SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, if (!f.file) return -EBADF;
- /* RED-PEN how should LSM module know it's handling 32bit? */ - error = security_file_ioctl(f.file, cmd, arg); + error = security_file_ioctl_compat(f.file, cmd, arg); if (error) goto out;
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 83ef66644c21..170687b5985b 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -751,7 +751,11 @@ static int ovl_security_fileattr(const struct path *realpath, struct fileattr *f else cmd = fa->fsx_valid ? FS_IOC_FSGETXATTR : FS_IOC_GETFLAGS;
+#ifdef CONFIG_COMPAT + err = security_file_ioctl_compat(file, cmd, 0); +# else err = security_file_ioctl(file, cmd, 0); +#endif fput(file);
return err; diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index ac962c4cb44b..626aa8cf930d 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -171,6 +171,8 @@ LSM_HOOK(int, 0, file_alloc_security, struct file *file) LSM_HOOK(void, LSM_RET_VOID, file_free_security, struct file *file) LSM_HOOK(int, 0, file_ioctl, struct file *file, unsigned int cmd, unsigned long arg) +LSM_HOOK(int, 0, file_ioctl_compat, struct file *file, unsigned int cmd, + unsigned long arg) LSM_HOOK(int, 0, mmap_addr, unsigned long addr) LSM_HOOK(int, 0, mmap_file, struct file *file, unsigned long reqprot, unsigned long prot, unsigned long flags) diff --git a/include/linux/security.h b/include/linux/security.h index 5f16eecde00b..22a82b7c59f1 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -389,6 +389,7 @@ int security_file_permission(struct file *file, int mask); int security_file_alloc(struct file *file); void security_file_free(struct file *file); int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg); +int security_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg); int security_mmap_file(struct file *file, unsigned long prot, unsigned long flags); int security_mmap_addr(unsigned long addr); @@ -987,6 +988,12 @@ static inline int security_file_ioctl(struct file *file, unsigned int cmd, return 0; }
+static inline int security_file_ioctl_compat(struct file *file, unsigned int cmd, + unsigned long arg) +{ + return 0; +} + static inline int security_mmap_file(struct file *file, unsigned long prot, unsigned long flags) { diff --git a/security/security.c b/security/security.c index 23b129d482a7..5c16ffc99b1e 100644 --- a/security/security.c +++ b/security/security.c @@ -2648,6 +2648,23 @@ int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg) } EXPORT_SYMBOL_GPL(security_file_ioctl);
+/** + * security_file_ioctl_compat() - Check if an ioctl is allowed in 32-bit compat mode + * @file: associated file + * @cmd: ioctl cmd + * @arg: ioctl arguments + * + * Compat version of security_file_ioctl() that correctly handles 32-bit processes + * running on 64-bit kernels. + * + * Return: Returns 0 if permission is granted. + */ +int security_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) +{ + return call_int_hook(file_ioctl_compat, 0, file, cmd, arg); +} +EXPORT_SYMBOL_GPL(security_file_ioctl_compat); + static inline unsigned long mmap_prot(struct file *file, unsigned long prot) { /* diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 2aa0e219d721..de96d156e6ea 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3731,6 +3731,31 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd, return error; }
+static int selinux_file_ioctl_compat(struct file *file, unsigned int cmd, + unsigned long arg) +{ + // If we are in a 64-bit kernel running 32-bit userspace, we need to make + // sure we don't compare 32-bit flags to 64-bit flags. + switch (cmd) { + case FS_IOC32_GETFLAGS: + cmd = FS_IOC_GETFLAGS; + break; + case FS_IOC32_SETFLAGS: + cmd = FS_IOC_GETFLAGS; + break; + case FS_IOC32_GETVERSION: + cmd = FS_IOC_GETVERSION; + break; + case FS_IOC32_SETVERSION: + cmd = FS_IOC_SETVERSION; + break; + default: + break; + } + + return selinux_file_ioctl(file, cmd, arg); +} + static int default_noexec __ro_after_init;
static int file_map_prot_check(struct file *file, unsigned long prot, int shared) @@ -7036,6 +7061,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = { LSM_HOOK_INIT(file_permission, selinux_file_permission), LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security), LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl), + LSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat), LSM_HOOK_INIT(mmap_file, selinux_mmap_file), LSM_HOOK_INIT(mmap_addr, selinux_mmap_addr), LSM_HOOK_INIT(file_mprotect, selinux_file_mprotect), diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 65130a791f57..1f1ea8529421 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -4973,6 +4973,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
LSM_HOOK_INIT(file_alloc_security, smack_file_alloc_security), LSM_HOOK_INIT(file_ioctl, smack_file_ioctl), + LSM_HOOK_INIT(file_ioctl_compat, smack_file_ioctl), LSM_HOOK_INIT(file_lock, smack_file_lock), LSM_HOOK_INIT(file_fcntl, smack_file_fcntl), LSM_HOOK_INIT(mmap_file, smack_mmap_file), diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c index 25006fddc964..298d182759c2 100644 --- a/security/tomoyo/tomoyo.c +++ b/security/tomoyo/tomoyo.c @@ -568,6 +568,7 @@ static struct security_hook_list tomoyo_hooks[] __ro_after_init = { LSM_HOOK_INIT(path_rename, tomoyo_path_rename), LSM_HOOK_INIT(inode_getattr, tomoyo_inode_getattr), LSM_HOOK_INIT(file_ioctl, tomoyo_file_ioctl), + LSM_HOOK_INIT(file_ioctl_compat, tomoyo_file_ioctl), LSM_HOOK_INIT(path_chmod, tomoyo_path_chmod), LSM_HOOK_INIT(path_chown, tomoyo_path_chown), LSM_HOOK_INIT(path_chroot, tomoyo_path_chroot),
base-commit: 196e95aa8305aecafc4e1857b7d3eff200d953b6
On Mon, Dec 18, 2023 at 7:43 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 emmits
s/emmits/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.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that replaces security_file_ioctl if the CONFIG_COMPAT flag is on. All current LSMs have been changed to hook into the compat flag.
It doesn't (or shouldn't) replace security_file_ioctl, and the hook doesn't appear to be conditional on CONFIG_COMPAT per se. It is a new hook that is called from the compat ioctl syscall. The old hook continues to be used from the regular ioctl syscall and elsewhere.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"") Signed-off-by: Alfred Piccioni alpic@google.com Cc: stable@vger.kernel.org
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 83ef66644c21..170687b5985b 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -751,7 +751,11 @@ static int ovl_security_fileattr(const struct path *realpath, struct fileattr *f else cmd = fa->fsx_valid ? FS_IOC_FSGETXATTR : FS_IOC_GETFLAGS;
+#ifdef CONFIG_COMPAT
err = security_file_ioctl_compat(file, cmd, 0);+# else err = security_file_ioctl(file, cmd, 0); +#endif
I don't understand why you made this change, possibly a leftover of an earlier version of the patch that tried to replace security_file_ioctl() everywhere?
On Mon, Dec 18, 2023 at 8:46 AM Stephen Smalley stephen.smalley.work@gmail.com wrote:
On Mon, Dec 18, 2023 at 7:43 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 emmits
s/emmits/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.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that replaces security_file_ioctl if the CONFIG_COMPAT flag is on. All current LSMs have been changed to hook into the compat flag.
It doesn't (or shouldn't) replace security_file_ioctl, and the hook doesn't appear to be conditional on CONFIG_COMPAT per se. It is a new hook that is called from the compat ioctl syscall. The old hook continues to be used from the regular ioctl syscall and elsewhere.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"") Signed-off-by: Alfred Piccioni alpic@google.com Cc: stable@vger.kernel.org
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 83ef66644c21..170687b5985b 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -751,7 +751,11 @@ static int ovl_security_fileattr(const struct path *realpath, struct fileattr *f else cmd = fa->fsx_valid ? FS_IOC_FSGETXATTR : FS_IOC_GETFLAGS;
+#ifdef CONFIG_COMPAT
err = security_file_ioctl_compat(file, cmd, 0);+# else err = security_file_ioctl(file, cmd, 0); +#endif
I don't understand why you made this change, possibly a leftover of an earlier version of the patch that tried to replace security_file_ioctl() everywhere?
By the way, for extra credit, you could augment the ioctl tests in the selinux-testsuite to also exercise this new hook and confirm that it works correctly. See https://github.com/SELinuxProject/selinux-testsuite particularly tests/ioctl and policy/test_ioctl.te. Feel free to ask for help on that.
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.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that is called from the compat ioctl syscall. All current LSMs have been changed to support this hook.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"") Signed-off-by: Alfred Piccioni alpic@google.com Cc: stable@vger.kernel.org --- fs/ioctl.c | 3 +-- include/linux/lsm_hook_defs.h | 2 ++ include/linux/security.h | 7 +++++++ security/security.c | 17 +++++++++++++++++ security/selinux/hooks.c | 28 ++++++++++++++++++++++++++++ security/smack/smack_lsm.c | 1 + security/tomoyo/tomoyo.c | 1 + 7 files changed, 57 insertions(+), 2 deletions(-)
diff --git a/fs/ioctl.c b/fs/ioctl.c index f5fd99d6b0d4..76cf22ac97d7 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -920,8 +920,7 @@ COMPAT_SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, if (!f.file) return -EBADF;
- /* RED-PEN how should LSM module know it's handling 32bit? */ - error = security_file_ioctl(f.file, cmd, arg); + error = security_file_ioctl_compat(f.file, cmd, arg); if (error) goto out;
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index ac962c4cb44b..626aa8cf930d 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -171,6 +171,8 @@ LSM_HOOK(int, 0, file_alloc_security, struct file *file) LSM_HOOK(void, LSM_RET_VOID, file_free_security, struct file *file) LSM_HOOK(int, 0, file_ioctl, struct file *file, unsigned int cmd, unsigned long arg) +LSM_HOOK(int, 0, file_ioctl_compat, struct file *file, unsigned int cmd, + unsigned long arg) LSM_HOOK(int, 0, mmap_addr, unsigned long addr) LSM_HOOK(int, 0, mmap_file, struct file *file, unsigned long reqprot, unsigned long prot, unsigned long flags) diff --git a/include/linux/security.h b/include/linux/security.h index 5f16eecde00b..22a82b7c59f1 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -389,6 +389,7 @@ int security_file_permission(struct file *file, int mask); int security_file_alloc(struct file *file); void security_file_free(struct file *file); int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg); +int security_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg); int security_mmap_file(struct file *file, unsigned long prot, unsigned long flags); int security_mmap_addr(unsigned long addr); @@ -987,6 +988,12 @@ static inline int security_file_ioctl(struct file *file, unsigned int cmd, return 0; }
+static inline int security_file_ioctl_compat(struct file *file, unsigned int cmd, + unsigned long arg) +{ + return 0; +} + static inline int security_mmap_file(struct file *file, unsigned long prot, unsigned long flags) { diff --git a/security/security.c b/security/security.c index 23b129d482a7..5c16ffc99b1e 100644 --- a/security/security.c +++ b/security/security.c @@ -2648,6 +2648,23 @@ int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg) } EXPORT_SYMBOL_GPL(security_file_ioctl);
+/** + * security_file_ioctl_compat() - Check if an ioctl is allowed in 32-bit compat mode + * @file: associated file + * @cmd: ioctl cmd + * @arg: ioctl arguments + * + * Compat version of security_file_ioctl() that correctly handles 32-bit processes + * running on 64-bit kernels. + * + * Return: Returns 0 if permission is granted. + */ +int security_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) +{ + return call_int_hook(file_ioctl_compat, 0, file, cmd, arg); +} +EXPORT_SYMBOL_GPL(security_file_ioctl_compat); + static inline unsigned long mmap_prot(struct file *file, unsigned long prot) { /* diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 2aa0e219d721..c617ae21dba8 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3731,6 +3731,33 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd, return error; }
+static int selinux_file_ioctl_compat(struct file *file, unsigned int cmd, + unsigned long arg) +{ + /* + * If we are in a 64-bit kernel running 32-bit userspace, we need to make + * sure we don't compare 32-bit flags to 64-bit flags. + */ + switch (cmd) { + case FS_IOC32_GETFLAGS: + cmd = FS_IOC_GETFLAGS; + break; + case FS_IOC32_SETFLAGS: + cmd = FS_IOC_SETFLAGS; + break; + case FS_IOC32_GETVERSION: + cmd = FS_IOC_GETVERSION; + break; + case FS_IOC32_SETVERSION: + cmd = FS_IOC_SETVERSION; + break; + default: + break; + } + + return selinux_file_ioctl(file, cmd, arg); +} + static int default_noexec __ro_after_init;
static int file_map_prot_check(struct file *file, unsigned long prot, int shared) @@ -7036,6 +7063,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = { LSM_HOOK_INIT(file_permission, selinux_file_permission), LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security), LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl), + LSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat), LSM_HOOK_INIT(mmap_file, selinux_mmap_file), LSM_HOOK_INIT(mmap_addr, selinux_mmap_addr), LSM_HOOK_INIT(file_mprotect, selinux_file_mprotect), diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 65130a791f57..1f1ea8529421 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -4973,6 +4973,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
LSM_HOOK_INIT(file_alloc_security, smack_file_alloc_security), LSM_HOOK_INIT(file_ioctl, smack_file_ioctl), + LSM_HOOK_INIT(file_ioctl_compat, smack_file_ioctl), LSM_HOOK_INIT(file_lock, smack_file_lock), LSM_HOOK_INIT(file_fcntl, smack_file_fcntl), LSM_HOOK_INIT(mmap_file, smack_mmap_file), diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c index 25006fddc964..298d182759c2 100644 --- a/security/tomoyo/tomoyo.c +++ b/security/tomoyo/tomoyo.c @@ -568,6 +568,7 @@ static struct security_hook_list tomoyo_hooks[] __ro_after_init = { LSM_HOOK_INIT(path_rename, tomoyo_path_rename), LSM_HOOK_INIT(inode_getattr, tomoyo_inode_getattr), LSM_HOOK_INIT(file_ioctl, tomoyo_file_ioctl), + LSM_HOOK_INIT(file_ioctl_compat, tomoyo_file_ioctl), LSM_HOOK_INIT(path_chmod, tomoyo_path_chmod), LSM_HOOK_INIT(path_chown, tomoyo_path_chown), LSM_HOOK_INIT(path_chroot, tomoyo_path_chroot),
base-commit: 196e95aa8305aecafc4e1857b7d3eff200d953b6
Thanks for taking the time to review! Apologies for the number of small mistakes.
s/syscal/syscall/ Might to consider checking using codespell to catch such things although it is imperfect.
Fixed, loaded codespell.
Paul doesn't like C++-style comments so rewrite using kernel coding style for multi-line comments or drop. I don't think kernel coding style strictly prohibits use for single-line comments and it isn't detected by checkpatch.pl but he has previously raised this on other patches. I actually like the C++-style comments for one-liners especially for comments at the end of a line of code but Paul is the maintainer so he gets the final word.
Changed to /**/ style comments. No particular preference on my side for comment structure, just used to C++/Java style.
Sorry, missed this the first time but cut-and-paste error above: s/GETFLAGS/SETFLAGS/
Egads. Fixed.
Also, IIRC, Paul prefers putting a pair of parentheses after function names to distinguish them, so in the subject line and description it should be security_file_ioctl_compat() and security_file_ioctl(), and you should put a patch version in the [PATCH] prefix e.g. [PATCH v3] to make clear that it is a later version, and usually one doesn't capitalize SELinux or the leading verb in the subject line (just "selinux: introduce").
Changed title to lower-case, prefixed with security, changed slightly to fit in summary with new parentheses. Added [PATCH V3] to the subject.
Actually, since this spans more than just SELinux, the prefix likely needs to reflect that (e.g. security: introduce ...) and the patch should go to the linux-security-module mailing list too and perhaps linux-fsdevel for the ioctl change.
Added cc 'selinux@vger.kernel.org' and cc 'linux-kernel@vger.kernel.org'. Thanks!
I didn't do an audit but does anything need to be updated for the BPF LSM or does it auto-magically pick up new hooks?
I'm unsure. I looked through the BPF LSM and I can't see any way it's picking up the file_ioctl hook to begin with. It appears to me skimming through the code that it automagically picks it up, but I'm not willing to bet the kernel on it.
Do you know who would be a good person to ask about this to make sure?
By the way, for extra credit, you could augment the ioctl tests in the selinux-testsuite to also exercise this new hook and confirm that it works correctly. See https://github.com/SELinuxProject/selinux-testsuite particularly tests/ioctl and policy/test_ioctl.te. Feel free to ask for help on that.
I do like extra credit. I'll take a look and see if it's something I can tackle. I'm primarily doing ad hoc checks on Android devices, so I'm unsure how easy it will be for me to run the suite. I'll get back to you shortly on that.
In response to myself, I unfortunately won't have time to do the testing updates this year. If someone else wants to help, that'd be great! Otherwise, I'll take a look next year after vacation and see if I can take a crack at it. Thanks!
On Tue, Dec 19, 2023 at 4:11 AM Alfred Piccioni alpic@google.com wrote:
Thanks for taking the time to review! Apologies for the number of small mistakes.
NP.
Also, IIRC, Paul prefers putting a pair of parentheses after function names to distinguish them, so in the subject line and description it should be security_file_ioctl_compat() and security_file_ioctl(), and you should put a patch version in the [PATCH] prefix e.g. [PATCH v3] to make clear that it is a later version, and usually one doesn't capitalize SELinux or the leading verb in the subject line (just "selinux: introduce").
Changed title to lower-case, prefixed with security, changed slightly to fit in summary with new parentheses. Added [PATCH V3] to the subject.
Patch description still doesn't include the parentheses after each function name but probably not worth re-spinning unless Paul says to do so. I don't see the v3 in the subject line. Seemingly that in combination with the fact that you replied to the original thread confuses the b4 tool (b4.docs.kernel.org) such that b4 mbox/am/shazam ends up selecting the v2 patch instead by default.
Actually, since this spans more than just SELinux, the prefix likely needs to reflect that (e.g. security: introduce ...) and the patch should go to the linux-security-module mailing list too and perhaps linux-fsdevel for the ioctl change.
Added cc 'selinux@vger.kernel.org' and cc 'linux-kernel@vger.kernel.org'. Thanks!
Just FYI, scripts/get_maintainer.pl /path/to/patch will provide an over-approximation of who to include on the distribution for patches based on MAINTAINERS and recent committers. That said, I generally prune the set it provides. More art than science.
I didn't do an audit but does anything need to be updated for the BPF LSM or does it auto-magically pick up new hooks?
I'm unsure. I looked through the BPF LSM and I can't see any way it's picking up the file_ioctl hook to begin with. It appears to me skimming through the code that it automagically picks it up, but I'm not willing to bet the kernel on it.
Do you know who would be a good person to ask about this to make sure?
Looks like it inherited it via the lsm_hook_defs.h. $ nm security/bpf/hooks.o | grep ioctl U bpf_lsm_file_ioctl U bpf_lsm_file_ioctl_compat
Adding BPF.
On 2023/12/19 18:10, Alfred Piccioni wrote:
I didn't do an audit but does anything need to be updated for the BPF LSM or does it auto-magically pick up new hooks?
I'm unsure. I looked through the BPF LSM and I can't see any way it's picking up the file_ioctl hook to begin with. It appears to me skimming through the code that it automagically picks it up, but I'm not willing to bet the kernel on it.
If BPF LSM silently picks up security_file_ioctl_compat() hook, I worry that some existing BPF programs which check ioctl() using BPF LSM fail to understand that such BPF programs need to be updated.
We basically don't care about out-of-tree kernel code. But does that rule apply to BPF programs? Since BPF programs are out-of-tree, are BPF programs which depend on BPF LSM considered as "we don't care about" rule? Or is breakage of existing BPF programs considered as a regression? (Note that this patch is CC:ed for stable kernels.)
Maybe BPF LSM should at least emit warning if the loaded BPF program defined security_file_ioctl() hook and did not define security_file_ioctl_compat() hook?
We could use a struct where undefined hooks needs to be manually filled with a dummy pointer, so that we can catch erroneously undefined hooks (detected by being automatically filled with a NULL pointer) at load time?
On Tue, Dec 19, 2023 at 4:09 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.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that is called from the compat ioctl syscall. All current LSMs have been changed to support this hook.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
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
On Tue, Dec 19, 2023 at 4:09 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.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that is called from the compat ioctl syscall. All current LSMs have been changed to support this hook.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"") Signed-off-by: Alfred Piccioni alpic@google.com Cc: stable@vger.kernel.org
fs/ioctl.c | 3 +-- include/linux/lsm_hook_defs.h | 2 ++ include/linux/security.h | 7 +++++++ security/security.c | 17 +++++++++++++++++ security/selinux/hooks.c | 28 ++++++++++++++++++++++++++++ security/smack/smack_lsm.c | 1 + security/tomoyo/tomoyo.c | 1 + 7 files changed, 57 insertions(+), 2 deletions(-)
diff --git a/fs/ioctl.c b/fs/ioctl.c index f5fd99d6b0d4..76cf22ac97d7 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -920,8 +920,7 @@ COMPAT_SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, if (!f.file) return -EBADF;
/* RED-PEN how should LSM module know it's handling 32bit? */error = security_file_ioctl(f.file, cmd, arg);
error = security_file_ioctl_compat(f.file, cmd, arg); if (error) goto out;
This is interesting ... if you look at the normal ioctl() syscall definition in the kernel you see 'ioctl(unsigned int fd, unsigned int cmd, unsigned long arg)' and if you look at the compat definition you see 'ioctl(unsigned int fd, unsigned int cmd, compat_ulong_t arg)'. I was expecting the second parameter, @cmd, to be a long type in the normal definition, but it is an int type in both cases. It looks like it has been that way long enough that it is correct, but I'm a little lost ...
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index ac962c4cb44b..626aa8cf930d 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -171,6 +171,8 @@ LSM_HOOK(int, 0, file_alloc_security, struct file *file) LSM_HOOK(void, LSM_RET_VOID, file_free_security, struct file *file) LSM_HOOK(int, 0, file_ioctl, struct file *file, unsigned int cmd, unsigned long arg) +LSM_HOOK(int, 0, file_ioctl_compat, struct file *file, unsigned int cmd,
unsigned long arg)LSM_HOOK(int, 0, mmap_addr, unsigned long addr) LSM_HOOK(int, 0, mmap_file, struct file *file, unsigned long reqprot, unsigned long prot, unsigned long flags) diff --git a/include/linux/security.h b/include/linux/security.h index 5f16eecde00b..22a82b7c59f1 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -389,6 +389,7 @@ int security_file_permission(struct file *file, int mask); int security_file_alloc(struct file *file); void security_file_free(struct file *file); int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg); +int security_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg); int security_mmap_file(struct file *file, unsigned long prot, unsigned long flags); int security_mmap_addr(unsigned long addr); @@ -987,6 +988,12 @@ static inline int security_file_ioctl(struct file *file, unsigned int cmd, return 0; }
+static inline int security_file_ioctl_compat(struct file *file, unsigned int cmd,
unsigned long arg)+{
return 0;+}
static inline int security_mmap_file(struct file *file, unsigned long prot, unsigned long flags) { diff --git a/security/security.c b/security/security.c index 23b129d482a7..5c16ffc99b1e 100644 --- a/security/security.c +++ b/security/security.c @@ -2648,6 +2648,23 @@ int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg) } EXPORT_SYMBOL_GPL(security_file_ioctl);
+/**
- security_file_ioctl_compat() - Check if an ioctl is allowed in 32-bit compat mode
- @file: associated file
- @cmd: ioctl cmd
- @arg: ioctl arguments
- Compat version of security_file_ioctl() that correctly handles 32-bit processes
- running on 64-bit kernels.
- Return: Returns 0 if permission is granted.
- */
+int security_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) +{
return call_int_hook(file_ioctl_compat, 0, file, cmd, arg);+} +EXPORT_SYMBOL_GPL(security_file_ioctl_compat);
static inline unsigned long mmap_prot(struct file *file, unsigned long prot) { /* diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 2aa0e219d721..c617ae21dba8 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3731,6 +3731,33 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd, return error; }
+static int selinux_file_ioctl_compat(struct file *file, unsigned int cmd,
unsigned long arg)+{
/** If we are in a 64-bit kernel running 32-bit userspace, we need to make* sure we don't compare 32-bit flags to 64-bit flags.*/switch (cmd) {case FS_IOC32_GETFLAGS:cmd = FS_IOC_GETFLAGS;break;case FS_IOC32_SETFLAGS:cmd = FS_IOC_SETFLAGS;break;case FS_IOC32_GETVERSION:cmd = FS_IOC_GETVERSION;break;case FS_IOC32_SETVERSION:cmd = FS_IOC_SETVERSION;break;default:break;}return selinux_file_ioctl(file, cmd, arg);+}
Is it considered valid for a native 64-bit task to use 32-bit FS_IO32_XXX flags? If not, do we want to remove the FS_IO32_XXX flag checks in selinux_file_ioctl()?
static int default_noexec __ro_after_init;
static int file_map_prot_check(struct file *file, unsigned long prot, int shared) @@ -7036,6 +7063,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = { LSM_HOOK_INIT(file_permission, selinux_file_permission), LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security), LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl),
LSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat), LSM_HOOK_INIT(mmap_file, selinux_mmap_file), LSM_HOOK_INIT(mmap_addr, selinux_mmap_addr), LSM_HOOK_INIT(file_mprotect, selinux_file_mprotect),diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 65130a791f57..1f1ea8529421 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -4973,6 +4973,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
LSM_HOOK_INIT(file_alloc_security, smack_file_alloc_security), LSM_HOOK_INIT(file_ioctl, smack_file_ioctl),
LSM_HOOK_INIT(file_ioctl_compat, smack_file_ioctl), LSM_HOOK_INIT(file_lock, smack_file_lock), LSM_HOOK_INIT(file_fcntl, smack_file_fcntl), LSM_HOOK_INIT(mmap_file, smack_mmap_file),diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c index 25006fddc964..298d182759c2 100644 --- a/security/tomoyo/tomoyo.c +++ b/security/tomoyo/tomoyo.c @@ -568,6 +568,7 @@ static struct security_hook_list tomoyo_hooks[] __ro_after_init = { LSM_HOOK_INIT(path_rename, tomoyo_path_rename), LSM_HOOK_INIT(inode_getattr, tomoyo_inode_getattr), LSM_HOOK_INIT(file_ioctl, tomoyo_file_ioctl),
LSM_HOOK_INIT(file_ioctl_compat, tomoyo_file_ioctl), LSM_HOOK_INIT(path_chmod, tomoyo_path_chmod), LSM_HOOK_INIT(path_chown, tomoyo_path_chown), LSM_HOOK_INIT(path_chroot, tomoyo_path_chroot),
I agree that it looks like Smack and TOMOYO should be fine, but I would like to hear from Casey and Tetsuo to confirm.
On 2023/12/23 10:23, Paul Moore wrote:
/* RED-PEN how should LSM module know it's handling 32bit? */error = security_file_ioctl(f.file, cmd, arg);
error = security_file_ioctl_compat(f.file, cmd, arg); if (error) goto out;This is interesting ... if you look at the normal ioctl() syscall definition in the kernel you see 'ioctl(unsigned int fd, unsigned int cmd, unsigned long arg)' and if you look at the compat definition you see 'ioctl(unsigned int fd, unsigned int cmd, compat_ulong_t arg)'. I was expecting the second parameter, @cmd, to be a long type in the normal definition, but it is an int type in both cases. It looks like it has been that way long enough that it is correct, but I'm a little lost ...
Since @arg might be a pointer to some struct, @arg needs to use a long type. But @cmd can remain 32bits for both 32bits/64bits kernels because @cmd is not a pointer, can't it?
I agree that it looks like Smack and TOMOYO should be fine, but I would like to hear from Casey and Tetsuo to confirm.
Fine for TOMOYO part, for TOMOYO treats @cmd as an integer.
On Sat, Dec 23, 2023 at 5:49 AM Tetsuo Handa penguin-kernel@i-love.sakura.ne.jp wrote:
On 2023/12/23 10:23, Paul Moore wrote:
/* RED-PEN how should LSM module know it's handling 32bit? */error = security_file_ioctl(f.file, cmd, arg);
error = security_file_ioctl_compat(f.file, cmd, arg); if (error) goto out;This is interesting ... if you look at the normal ioctl() syscall definition in the kernel you see 'ioctl(unsigned int fd, unsigned int cmd, unsigned long arg)' and if you look at the compat definition you see 'ioctl(unsigned int fd, unsigned int cmd, compat_ulong_t arg)'. I was expecting the second parameter, @cmd, to be a long type in the normal definition, but it is an int type in both cases. It looks like it has been that way long enough that it is correct, but I'm a little lost ...
Since @arg might be a pointer to some struct, @arg needs to use a long type. But @cmd can remain 32bits for both 32bits/64bits kernels because @cmd is not a pointer, can't it?
I'm not worried about @arg, I'm worried about @cmd, the second parameter to the syscall. I was looking at the manpage and it is specified as an unsigned long, which would be a size mismatch on a 64-bit system, although now that I'm reading further into the manpage I see that the command is specified as a 32-bit value so an int shouldn't be a problem. I'm guessing the unsigned long type persists from the days before 64-bit systems.
I agree that it looks like Smack and TOMOYO should be fine, but I would like to hear from Casey and Tetsuo to confirm.
Fine for TOMOYO part, for TOMOYO treats @cmd as an integer.
Great, thank you.
On Fri, Dec 22, 2023 at 08:23:26PM -0500, Paul Moore wrote:
Is it considered valid for a native 64-bit task to use 32-bit FS_IO32_XXX flags?
No, that's not valid.
If not, do we want to remove the FS_IO32_XXX flag checks in selinux_file_ioctl()?
I don't see any such flag checks in selinux_file_ioctl().
Is there something else you have in mind?
- Eric
On Sat, Dec 23, 2023 at 10:34 AM Eric Biggers ebiggers@kernel.org wrote:
On Fri, Dec 22, 2023 at 08:23:26PM -0500, Paul Moore wrote:
Is it considered valid for a native 64-bit task to use 32-bit FS_IO32_XXX flags?
No, that's not valid.
Excellent, thank you.
If not, do we want to remove the FS_IO32_XXX flag checks in selinux_file_ioctl()?
I don't see any such flag checks in selinux_file_ioctl().
Neither do I ... I'm not sure what I was looking at when I made that comment, I'm going to chalk that up to a bit of holiday fog. Sorry for the noise.
Is there something else you have in mind?
Nope.
On Sun, Dec 24, 2023 at 3:00 PM Paul Moore paul@paul-moore.com wrote:
On Sat, Dec 23, 2023 at 10:34 AM Eric Biggers ebiggers@kernel.org wrote:
On Fri, Dec 22, 2023 at 08:23:26PM -0500, Paul Moore wrote:
Is it considered valid for a native 64-bit task to use 32-bit FS_IO32_XXX flags?
No, that's not valid.
Excellent, thank you.
If not, do we want to remove the FS_IO32_XXX flag checks in selinux_file_ioctl()?
I don't see any such flag checks in selinux_file_ioctl().
Neither do I ... I'm not sure what I was looking at when I made that comment, I'm going to chalk that up to a bit of holiday fog. Sorry for the noise.
Ah ha, I think I found the problem - the tools I use to pull in patches for review seemed to have grabbed an old version of the patch that *did* as the 32-bit ioctl commands to selinux_file_ioctl().
https://lore.kernel.org/selinux/20230906102557.3432236-1-alpic@google.com/
On 12/22/2023 5:23 PM, Paul Moore wrote:
On Tue, Dec 19, 2023 at 4:09 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.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that is called from the compat ioctl syscall. All current LSMs have been changed to support this hook.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"") Signed-off-by: Alfred Piccioni alpic@google.com Cc: stable@vger.kernel.org
fs/ioctl.c | 3 +-- include/linux/lsm_hook_defs.h | 2 ++ include/linux/security.h | 7 +++++++ security/security.c | 17 +++++++++++++++++ security/selinux/hooks.c | 28 ++++++++++++++++++++++++++++ security/smack/smack_lsm.c | 1 + security/tomoyo/tomoyo.c | 1 + 7 files changed, 57 insertions(+), 2 deletions(-)
diff --git a/fs/ioctl.c b/fs/ioctl.c index f5fd99d6b0d4..76cf22ac97d7 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -920,8 +920,7 @@ COMPAT_SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, if (!f.file) return -EBADF;
/* RED-PEN how should LSM module know it's handling 32bit? */error = security_file_ioctl(f.file, cmd, arg);
error = security_file_ioctl_compat(f.file, cmd, arg); if (error) goto out;This is interesting ... if you look at the normal ioctl() syscall definition in the kernel you see 'ioctl(unsigned int fd, unsigned int cmd, unsigned long arg)' and if you look at the compat definition you see 'ioctl(unsigned int fd, unsigned int cmd, compat_ulong_t arg)'. I was expecting the second parameter, @cmd, to be a long type in the normal definition, but it is an int type in both cases. It looks like it has been that way long enough that it is correct, but I'm a little lost ...
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index ac962c4cb44b..626aa8cf930d 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -171,6 +171,8 @@ LSM_HOOK(int, 0, file_alloc_security, struct file *file) LSM_HOOK(void, LSM_RET_VOID, file_free_security, struct file *file) LSM_HOOK(int, 0, file_ioctl, struct file *file, unsigned int cmd, unsigned long arg) +LSM_HOOK(int, 0, file_ioctl_compat, struct file *file, unsigned int cmd,
unsigned long arg)LSM_HOOK(int, 0, mmap_addr, unsigned long addr) LSM_HOOK(int, 0, mmap_file, struct file *file, unsigned long reqprot, unsigned long prot, unsigned long flags) diff --git a/include/linux/security.h b/include/linux/security.h index 5f16eecde00b..22a82b7c59f1 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -389,6 +389,7 @@ int security_file_permission(struct file *file, int mask); int security_file_alloc(struct file *file); void security_file_free(struct file *file); int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg); +int security_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg); int security_mmap_file(struct file *file, unsigned long prot, unsigned long flags); int security_mmap_addr(unsigned long addr); @@ -987,6 +988,12 @@ static inline int security_file_ioctl(struct file *file, unsigned int cmd, return 0; }
+static inline int security_file_ioctl_compat(struct file *file, unsigned int cmd,
unsigned long arg)+{
return 0;+}
static inline int security_mmap_file(struct file *file, unsigned long prot, unsigned long flags) { diff --git a/security/security.c b/security/security.c index 23b129d482a7..5c16ffc99b1e 100644 --- a/security/security.c +++ b/security/security.c @@ -2648,6 +2648,23 @@ int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg) } EXPORT_SYMBOL_GPL(security_file_ioctl);
+/**
- security_file_ioctl_compat() - Check if an ioctl is allowed in 32-bit compat mode
- @file: associated file
- @cmd: ioctl cmd
- @arg: ioctl arguments
- Compat version of security_file_ioctl() that correctly handles 32-bit processes
- running on 64-bit kernels.
- Return: Returns 0 if permission is granted.
- */
+int security_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) +{
return call_int_hook(file_ioctl_compat, 0, file, cmd, arg);+} +EXPORT_SYMBOL_GPL(security_file_ioctl_compat);
static inline unsigned long mmap_prot(struct file *file, unsigned long prot) { /* diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 2aa0e219d721..c617ae21dba8 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -3731,6 +3731,33 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd, return error; }
+static int selinux_file_ioctl_compat(struct file *file, unsigned int cmd,
unsigned long arg)+{
/** If we are in a 64-bit kernel running 32-bit userspace, we need to make* sure we don't compare 32-bit flags to 64-bit flags.*/switch (cmd) {case FS_IOC32_GETFLAGS:cmd = FS_IOC_GETFLAGS;break;case FS_IOC32_SETFLAGS:cmd = FS_IOC_SETFLAGS;break;case FS_IOC32_GETVERSION:cmd = FS_IOC_GETVERSION;break;case FS_IOC32_SETVERSION:cmd = FS_IOC_SETVERSION;break;default:break;}return selinux_file_ioctl(file, cmd, arg);+}
Is it considered valid for a native 64-bit task to use 32-bit FS_IO32_XXX flags? If not, do we want to remove the FS_IO32_XXX flag checks in selinux_file_ioctl()?
static int default_noexec __ro_after_init;
static int file_map_prot_check(struct file *file, unsigned long prot, int shared) @@ -7036,6 +7063,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = { LSM_HOOK_INIT(file_permission, selinux_file_permission), LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security), LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl),
LSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat), LSM_HOOK_INIT(mmap_file, selinux_mmap_file), LSM_HOOK_INIT(mmap_addr, selinux_mmap_addr), LSM_HOOK_INIT(file_mprotect, selinux_file_mprotect),diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 65130a791f57..1f1ea8529421 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -4973,6 +4973,7 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
LSM_HOOK_INIT(file_alloc_security, smack_file_alloc_security), LSM_HOOK_INIT(file_ioctl, smack_file_ioctl),
LSM_HOOK_INIT(file_ioctl_compat, smack_file_ioctl), LSM_HOOK_INIT(file_lock, smack_file_lock), LSM_HOOK_INIT(file_fcntl, smack_file_fcntl), LSM_HOOK_INIT(mmap_file, smack_mmap_file),diff --git a/security/tomoyo/tomoyo.c b/security/tomoyo/tomoyo.c index 25006fddc964..298d182759c2 100644 --- a/security/tomoyo/tomoyo.c +++ b/security/tomoyo/tomoyo.c @@ -568,6 +568,7 @@ static struct security_hook_list tomoyo_hooks[] __ro_after_init = { LSM_HOOK_INIT(path_rename, tomoyo_path_rename), LSM_HOOK_INIT(inode_getattr, tomoyo_inode_getattr), LSM_HOOK_INIT(file_ioctl, tomoyo_file_ioctl),
LSM_HOOK_INIT(file_ioctl_compat, tomoyo_file_ioctl), LSM_HOOK_INIT(path_chmod, tomoyo_path_chmod), LSM_HOOK_INIT(path_chown, tomoyo_path_chown), LSM_HOOK_INIT(path_chroot, tomoyo_path_chroot),I agree that it looks like Smack and TOMOYO should be fine, but I would like to hear from Casey and Tetsuo to confirm.
Smack should be OK.
On Tue, Dec 19, 2023 at 4:09 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.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that is called from the compat ioctl syscall. All current LSMs have been changed to support this hook.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"") Signed-off-by: Alfred Piccioni alpic@google.com Cc: stable@vger.kernel.org
fs/ioctl.c | 3 +-- include/linux/lsm_hook_defs.h | 2 ++ include/linux/security.h | 7 +++++++ security/security.c | 17 +++++++++++++++++ security/selinux/hooks.c | 28 ++++++++++++++++++++++++++++ security/smack/smack_lsm.c | 1 + security/tomoyo/tomoyo.c | 1 + 7 files changed, 57 insertions(+), 2 deletions(-)
I made some minor style tweaks around line length and alignment, but otherwise this looked good to me. Thanks all!
While I agree this is definitely stable kernel material, given where we are at in the current kernel cycle, and with the end-of-year holidays in full swing, I'm going to merge this into lsm/dev and send it up to Linus during the next merge window. The stable tag will remain intact, so it will end up trickling down into the stable kernels, it will just take an extra week or so (which I think will be good from a testing perspective).
On Sun, Dec 24, 2023 at 03:53:16PM -0500, Paul Moore wrote:
On Tue, Dec 19, 2023 at 4:09 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.
This was also noted in a RED-PEN finding from a while back - "/* RED-PEN how should LSM module know it's handling 32bit? */".
This patch introduces a new hook, security_file_ioctl_compat, that is called from the compat ioctl syscall. All current LSMs have been changed to support this hook.
Reviewing the three places where we are currently using security_file_ioctl, it appears that only SELinux needs a dedicated compat change; TOMOYO and SMACK appear to be functional without any change.
Fixes: 0b24dcb7f2f7 ("Revert "selinux: simplify ioctl checking"") Signed-off-by: Alfred Piccioni alpic@google.com Cc: stable@vger.kernel.org
fs/ioctl.c | 3 +-- include/linux/lsm_hook_defs.h | 2 ++ include/linux/security.h | 7 +++++++ security/security.c | 17 +++++++++++++++++ security/selinux/hooks.c | 28 ++++++++++++++++++++++++++++ security/smack/smack_lsm.c | 1 + security/tomoyo/tomoyo.c | 1 + 7 files changed, 57 insertions(+), 2 deletions(-)
I made some minor style tweaks around line length and alignment, but otherwise this looked good to me. Thanks all!
Reviewed-by: Eric Biggers ebiggers@google.com
(I reviewed the version in branch "next" of https://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm.git)
- Eric
linux-stable-mirror@lists.linaro.org
-
Alfred Piccioni -
Casey Schaufler -
Eric Biggers -
kernel test robot -
Mickaël Salaün -
Paul Moore -
Stephen Smalley -
Tetsuo Handa