diff --git a/keystore2/src/permission.rs b/keystore2/src/permission.rs
index 7bf17b5..023774f 100644
--- a/keystore2/src/permission.rs
+++ b/keystore2/src/permission.rs
@@ -282,12 +282,19 @@
 ///                      SELinux keystore key backend, and the result is used
 ///                      as target context.
 pub fn check_grant_permission(
+    caller_uid: u32,
     caller_ctx: &CStr,
     access_vec: KeyPermSet,
     key: &KeyDescriptor,
 ) -> anyhow::Result<()> {
     let target_context = match key.domain {
-        Domain::APP => getcon().context("check_grant_permission: getcon failed.")?,
+        Domain::APP => {
+            if caller_uid as i64 != key.nspace {
+                return Err(selinux::Error::perm())
+                    .context("Trying to access key without ownership.");
+            }
+            getcon().context("check_grant_permission: getcon failed.")?
+        }
         Domain::SELINUX => lookup_keystore2_key_context(key.nspace)
             .context("check_grant_permission: Domain::SELINUX: Failed to lookup namespace.")?,
         _ => return Err(KsError::sys()).context(format!("Cannot grant {:?}.", key.domain)),
diff --git a/keystore2/src/permission/tests.rs b/keystore2/src/permission/tests.rs
index c9aebfe..68c9b74 100644
--- a/keystore2/src/permission/tests.rs
+++ b/keystore2/src/permission/tests.rs
@@ -135,11 +135,11 @@
 fn check_grant_permission_app() -> Result<()> {
     let system_server_ctx = Context::new("u:r:system_server:s0")?;
     let key = KeyDescriptor { domain: Domain::APP, nspace: 0, alias: None, blob: None };
-    check_grant_permission(&system_server_ctx, SYSTEM_SERVER_PERMISSIONS_NO_GRANT, &key)
+    check_grant_permission(0, &system_server_ctx, SYSTEM_SERVER_PERMISSIONS_NO_GRANT, &key)
         .expect("Grant permission check failed.");
 
     // attempts to grant the grant permission must always fail even when privileged.
-    assert_perm_failed!(check_grant_permission(&system_server_ctx, KeyPerm::Grant.into(), &key));
+    assert_perm_failed!(check_grant_permission(0, &system_server_ctx, KeyPerm::Grant.into(), &key));
     Ok(())
 }
 
@@ -153,12 +153,12 @@
         blob: None,
     };
     if is_su {
-        assert!(check_grant_permission(&sctx, NOT_GRANT_PERMS, &key).is_ok());
+        assert!(check_grant_permission(0, &sctx, NOT_GRANT_PERMS, &key).is_ok());
         // attempts to grant the grant permission must always fail even when privileged.
-        assert_perm_failed!(check_grant_permission(&sctx, KeyPerm::Grant.into(), &key));
+        assert_perm_failed!(check_grant_permission(0, &sctx, KeyPerm::Grant.into(), &key));
     } else {
         // unprivileged grant attempts always fail. shell does not have the grant permission.
-        assert_perm_failed!(check_grant_permission(&sctx, UNPRIV_PERMS, &key));
+        assert_perm_failed!(check_grant_permission(0, &sctx, UNPRIV_PERMS, &key));
     }
     Ok(())
 }
diff --git a/keystore2/src/utils.rs b/keystore2/src/utils.rs
index 2b69d1e..c6dc11e 100644
--- a/keystore2/src/utils.rs
+++ b/keystore2/src/utils.rs
@@ -80,6 +80,7 @@
 pub fn check_grant_permission(access_vec: KeyPermSet, key: &KeyDescriptor) -> anyhow::Result<()> {
     ThreadState::with_calling_sid(|calling_sid| {
         permission::check_grant_permission(
+            ThreadState::get_calling_uid(),
             calling_sid
                 .ok_or_else(Error::sys)
                 .context(ks_err!("Cannot check permission without calling_sid."))?,