UBUNTU: SAUCE: apparmor: fix nnp subset check failure when, stacking

This is a backport of a fix that landed as part of a larger patch
in 4.17 commit 9fcf78cca1986 ("apparmor: update domain transitions that are subsets of confinement at nnp")

Domain transitions that add a new profile to the confinement stack
when under NO NEW PRIVS is allowed as it can not expand privileges.

However such transitions are failing due to how/where the subset
test is being applied. Applying the test per profile in the
profile transition and profile_onexec call backs is incorrect as
it disregards the other profiles in the stack so it can not
correctly determine if the old confinement stack is a subset of
the new confinement stack.

Move the test to after the new confinement stack is constructed.

BugLink: http://bugs.launchpad.net/bugs/1839037
Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c
index 9921f5364840f3e79ad3693faa47ecea8e9820ae..76cebad829fadf5a4c30bd9167a950cfcd8052ad 100644 (file)
--- a/security/apparmor/domain.c
+++ b/security/apparmor/domain.c
@@ -592,22 +592,6 @@ static struct aa_label *profile_transition(struct aa_profile *profile,
        if (!new)
                goto audit;
 
-       /* Policy has specified a domain transitions. if no_new_privs and
-        * confined and not transitioning to the current domain fail.
-        *
-        * NOTE: Domain transitions from unconfined and to stritly stacked
-        * subsets are allowed even when no_new_privs is set because this
-        * aways results in a further reduction of permissions.
-        */
-       if ((bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) &&
-           !profile_unconfined(profile) &&
-           !aa_label_is_subset(new, &profile->label)) {
-               error = -EPERM;
-               info = "no new privs";
-               nonewprivs = true;
-               perms.allow &= ~MAY_EXEC;
-               goto audit;
-       }
 
        if (!(perms.xindex & AA_X_UNSAFE)) {
                if (DEBUG_ON) {
@@ -684,21 +668,6 @@ static int profile_onexec(struct aa_profile *profile, struct aa_label *onexec,
                perms.allow &= ~AA_MAY_ONEXEC;
                goto audit;
        }
-       /* Policy has specified a domain transitions. if no_new_privs and
-        * confined and not transitioning to the current domain fail.
-        *
-        * NOTE: Domain transitions from unconfined and to stritly stacked
-        * subsets are allowed even when no_new_privs is set because this
-        * aways results in a further reduction of permissions.
-        */
-       if ((bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) &&
-           !profile_unconfined(profile) &&
-           !aa_label_is_subset(onexec, &profile->label)) {
-               error = -EPERM;
-               info = "no new privs";
-               perms.allow &= ~AA_MAY_ONEXEC;
-               goto audit;
-       }
 
        if (!(perms.xindex & AA_X_UNSAFE)) {
                if (DEBUG_ON) {
@@ -819,7 +788,20 @@ int apparmor_bprm_set_creds(struct linux_binprm *bprm)
                goto done;
        }
 
-       /* TODO: Add ns level no_new_privs subset test */
+       /* Policy has specified a domain transitions. If no_new_privs and
+        * confined ensure the transition is to confinement that is subset
+        * of the confinement when the task entered no new privs.
+        *
+        * NOTE: Domain transitions from unconfined and to stacked
+        * subsets are allowed even when no_new_privs is set because this
+        * aways results in a further reduction of permissions.
+        */
+       if ((bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS) &&
+           !unconfined(label) && !aa_label_is_subset(new, label)) {
+               error = -EPERM;
+               info = "no new privs";
+               goto audit;
+       }
 
        if (bprm->unsafe & LSM_UNSAFE_SHARE) {
                /* FIXME: currently don't mediate shared state */