userns: Convert capabilities related permsion checks

- Use uid_eq when comparing kuids
  Use gid_eq when comparing kgids
- Use make_kuid(user_ns, 0) to talk about the user_namespace root uid

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

1 files changed, 26 insertions, 15 deletions

diff --git a/security/commoncap.c b/security/commoncap.c
index dbd465a59286..ff9b113bb07c 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -472,19 +472,22 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
         struct cred *new = bprm->cred;
         bool effective, has_cap = false;
         int ret;
+        kuid_t root_uid;
 
         effective = false;
         ret = get_file_caps(bprm, &effective, &has_cap);
         if (ret < 0)
                 return ret;
 
+        root_uid = make_kuid(new->user_ns, 0);
+
         if (!issecure(SECURE_NOROOT)) {
                 /*
                  * If the legacy file capability is set, then don't set privs
                  * for a setuid root binary run by a non-root user.  Do set it
                  * for a root user just to cause least surprise to an admin.
                  */
-                if (has_cap && new->uid != 0 && new->euid == 0) {
+                if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
                         warn_setuid_and_fcaps_mixed(bprm->filename);
                         goto skip;
                 }
@@ -495,12 +498,12 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
                  *
                  * If only the real uid is 0, we do not set the effective bit.
                  */
-                if (new->euid == 0 || new->uid == 0) {
+                if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
                         /* pP' = (cap_bset & ~0) | (pI & ~0) */
                         new->cap_permitted = cap_combine(old->cap_bset,
                                                          old->cap_inheritable);
                 }
-                if (new->euid == 0)
+                if (uid_eq(new->euid, root_uid))
                         effective = true;
         }
 skip:
@@ -508,8 +511,8 @@ skip:
         /* Don't let someone trace a set[ug]id/setpcap binary with the revised
          * credentials unless they have the appropriate permit
          */
-        if ((new->euid != old->uid ||
-             new->egid != old->gid ||
+        if ((!uid_eq(new->euid, old->uid) ||
+             !gid_eq(new->egid, old->gid) ||
              !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
             bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
                 /* downgrade; they get no more than they had, and maybe less */
@@ -544,7 +547,7 @@ skip:
          */
         if (!cap_isclear(new->cap_effective)) {
                 if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
-                    new->euid != 0 || new->uid != 0 ||
+                    !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
                     issecure(SECURE_NOROOT)) {
                         ret = audit_log_bprm_fcaps(bprm, new, old);
                         if (ret < 0)
@@ -569,16 +572,17 @@ skip:
 int cap_bprm_secureexec(struct linux_binprm *bprm)
 {
         const struct cred *cred = current_cred();
+        kuid_t root_uid = make_kuid(cred->user_ns, 0);
 
-        if (cred->uid != 0) {
+        if (!uid_eq(cred->uid, root_uid)) {
                 if (bprm->cap_effective)
                         return 1;
                 if (!cap_isclear(cred->cap_permitted))
                         return 1;
         }
 
-        return (cred->euid != cred->uid ||
-                cred->egid != cred->gid);
+        return (!uid_eq(cred->euid, cred->uid) ||
+                !gid_eq(cred->egid, cred->gid));
 }
 
 /**
@@ -668,15 +672,21 @@ int cap_inode_removexattr(struct dentry *dentry, const char *name)
  */
 static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
 {
-        if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
-            (new->uid != 0 && new->euid != 0 && new->suid != 0) &&
+        kuid_t root_uid = make_kuid(old->user_ns, 0);
+
+        if ((uid_eq(old->uid, root_uid) ||
+             uid_eq(old->euid, root_uid) ||
+             uid_eq(old->suid, root_uid)) &&
+            (!uid_eq(new->uid, root_uid) &&
+             !uid_eq(new->euid, root_uid) &&
+             !uid_eq(new->suid, root_uid)) &&
             !issecure(SECURE_KEEP_CAPS)) {
                 cap_clear(new->cap_permitted);
                 cap_clear(new->cap_effective);
         }
-        if (old->euid == 0 && new->euid != 0)
+        if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
                 cap_clear(new->cap_effective);
-        if (old->euid != 0 && new->euid == 0)
+        if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
                 new->cap_effective = new->cap_permitted;
 }
 
@@ -709,11 +719,12 @@ int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
                  *          if not, we might be a bit too harsh here.
                  */
                 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
-                        if (old->fsuid == 0 && new->fsuid != 0)
+                        kuid_t root_uid = make_kuid(old->user_ns, 0);
+                        if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
                                 new->cap_effective =
                                         cap_drop_fs_set(new->cap_effective);
 
-                        if (old->fsuid != 0 && new->fsuid == 0)
+                        if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
                                 new->cap_effective =
                                         cap_raise_fs_set(new->cap_effective,
                                                          new->cap_permitted);