TOMOYO: Fix mount flags checking order.

BugLink: http://bugs.launchpad.net/bugs/981162

commit df91e49477a9be15921cb2854e1d12a3bdb5e425 upstream.

Userspace can pass in arbitrary combinations of MS_* flags to mount().

If both MS_BIND and one of MS_SHARED/MS_PRIVATE/MS_SLAVE/MS_UNBINDABLE are
passed, device name which should be checked for MS_BIND was not checked because
MS_SHARED/MS_PRIVATE/MS_SLAVE/MS_UNBINDABLE had higher priority than MS_BIND.

If both one of MS_BIND/MS_MOVE and MS_REMOUNT are passed, device name which
should not be checked for MS_REMOUNT was checked because MS_BIND/MS_MOVE had
higher priority than MS_REMOUNT.

Fix these bugs by changing priority to MS_REMOUNT -> MS_BIND ->
MS_SHARED/MS_PRIVATE/MS_SLAVE/MS_UNBINDABLE -> MS_MOVE as with do_mount() does.

Also, unconditionally return -EINVAL if more than one of
MS_SHARED/MS_PRIVATE/MS_SLAVE/MS_UNBINDABLE is passed so that TOMOYO will not
generate inaccurate audit logs, for commit 7a2e8a8f "VFS: Sanity check mount
flags passed to change_mnt_propagation()" clarified that these flags must be
exclusively passed.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

diff --git a/security/tomoyo/mount.c b/security/tomoyo/mount.c
index bee09d0..fe00cdf 100644 (file)
--- a/security/tomoyo/mount.c
+++ b/security/tomoyo/mount.c
@@ -199,30 +199,32 @@ int tomoyo_mount_permission(char *dev_name, struct path *path,
        if (flags & MS_REMOUNT) {
                type = tomoyo_mounts[TOMOYO_MOUNT_REMOUNT];
                flags &= ~MS_REMOUNT;
-       }
-       if (flags & MS_MOVE) {
-               type = tomoyo_mounts[TOMOYO_MOUNT_MOVE];
-               flags &= ~MS_MOVE;
-       }
-       if (flags & MS_BIND) {
+       } else if (flags & MS_BIND) {
                type = tomoyo_mounts[TOMOYO_MOUNT_BIND];
                flags &= ~MS_BIND;
-       }
-       if (flags & MS_UNBINDABLE) {
-               type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE];
-               flags &= ~MS_UNBINDABLE;
-       }
-       if (flags & MS_PRIVATE) {
+       } else if (flags & MS_SHARED) {
+               if (flags & (MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
+                       return -EINVAL;
+               type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED];
+               flags &= ~MS_SHARED;
+       } else if (flags & MS_PRIVATE) {
+               if (flags & (MS_SHARED | MS_SLAVE | MS_UNBINDABLE))
+                       return -EINVAL;
                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE];
                flags &= ~MS_PRIVATE;
-       }
-       if (flags & MS_SLAVE) {
+       } else if (flags & MS_SLAVE) {
+               if (flags & (MS_SHARED | MS_PRIVATE | MS_UNBINDABLE))
+                       return -EINVAL;
                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE];
                flags &= ~MS_SLAVE;
-       }
-       if (flags & MS_SHARED) {
-               type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED];
-               flags &= ~MS_SHARED;
+       } else if (flags & MS_UNBINDABLE) {
+               if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE))
+                       return -EINVAL;
+               type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE];
+               flags &= ~MS_UNBINDABLE;
+       } else if (flags & MS_MOVE) {
+               type = tomoyo_mounts[TOMOYO_MOUNT_MOVE];
+               flags &= ~MS_MOVE;
        }
        if (!type)
                type = "<NULL>";