From patchwork Wed Nov 10 23:00:34 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Todd Kjos X-Patchwork-Id: 12613541 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 74D53C433EF for ; Wed, 10 Nov 2021 23:00:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5DB3C6108B for ; Wed, 10 Nov 2021 23:00:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234159AbhKJXD3 (ORCPT ); Wed, 10 Nov 2021 18:03:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46434 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233150AbhKJXD2 (ORCPT ); Wed, 10 Nov 2021 18:03:28 -0500 Received: from mail-qv1-xf4a.google.com (mail-qv1-xf4a.google.com [IPv6:2607:f8b0:4864:20::f4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BE0B3C061766 for ; Wed, 10 Nov 2021 15:00:40 -0800 (PST) Received: by mail-qv1-xf4a.google.com with SMTP id kd7-20020a056214400700b003b54713452cso3995923qvb.13 for ; Wed, 10 Nov 2021 15:00:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=B5qR9IFfPYyqZzAR1NtxHfHPCrwSatA1W5mjCxV+NDo=; b=dxpfCGJxE0aLuP6SejLibiTWJsNl6eV6c/7AD/qBuov+nxRRy9M+Huw3sdeCqSw3xv untZb7uJRe2oloH8KlA+ToFNZyo1bQX1//VSPZG1xBzkjFFmXQ8FUT0loiOBRk/qzJQ+ vUFvWT9J8gW7RNdvL06j01uuCWnmRV4JaOhGfxGF/4xo3f7jewGnfVu/v8rQDnTqCv63 vbIOKJhptN6quN5JVzvqlOdqkPmVW0QhGrE+OVgPBU+w1jzf9h4Q2dIgNefrreNPlTZt NOf9feJkkaU36k5lWJJBZaNmDy6lqNrPoJ4cLXDaA8pj5JkDO/RivBeoALWPLGPNC18B RCew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=B5qR9IFfPYyqZzAR1NtxHfHPCrwSatA1W5mjCxV+NDo=; b=dzadLFFbdVMRb2xmITP7d1cqnvGO4ilqdWtphUqhXPdu+DruyDR9hJ4MNEZ1x9zzul tykRfWg5qYYxBuhJh89jqmximFGaH0tfEZPssR5bpyBqCbPxuo6Ow5C4F1WkEXCusqU3 5tuVUTPQyM9reff2nMknvvEHLmtg/0JQgaKg9R3AgkYr0RN3Wxj5JpGL9LDslFpXCLWi mjuNyhKrTw7vvePW4vF0jbWjT5C1fd3fGpRGv7IvH/GEFFE9L5KeYKcputX2EJ0sWqSn /Y3hWCNwzrS2zVg5RAQN+77ammP9E1UegRBDblhaJTEFMHSvmuNN5Hshwi02cMDD+dtk QSVA== X-Gm-Message-State: AOAM5321sqyHZU5g/Pevw6FLWp73v3AnJqS5v0qhzFV1B6HklcEFr8rH jTBPNj+JC8HSWQY4Uk3aYyK1iH5sIg== X-Google-Smtp-Source: ABdhPJxNeI9pPQMczNqh7lTEOTjZOwslOwZWyiK/KZOlDPOiuxMgX0yqvhob/VWngaHy4gSf0G3hdmOstQ== X-Received: from tkjos-desktop.mtv.corp.google.com ([2620:15c:211:200:4a73:99b6:9694:8c4d]) (user=tkjos job=sendgmr) by 2002:a05:622a:20d:: with SMTP id b13mr2915118qtx.368.1636585239970; Wed, 10 Nov 2021 15:00:39 -0800 (PST) Date: Wed, 10 Nov 2021 15:00:34 -0800 Message-Id: <20211110230036.3274365-1-tkjos@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.34.0.rc0.344.g81b53c2807-goog Subject: [PATCH 5.10 1/3] binder: use euid from cred instead of using task From: Todd Kjos To: stable@vger.kernel.org, gregkh@linuxfoundation.org, arve@android.com, tkjos@android.com, maco@android.com, christian@brauner.io, jmorris@namei.org, serge@hallyn.com, paul@paul-moore.com, stephen.smalley.work@gmail.com, eparis@parisplace.org, keescook@chromium.org, jannh@google.com, jeffv@google.com, zohar@linux.ibm.com, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, devel@driverdev.osuosl.org Cc: joel@joelfernandes.org, kernel-team@android.com, Todd Kjos , Casey Schaufler Precedence: bulk List-ID: commit 29bc22ac5e5bc63275e850f0c8fc549e3d0e306b upstream. Save the 'struct cred' associated with a binder process at initial open to avoid potential race conditions when converting to an euid. Set a transaction's sender_euid from the 'struct cred' saved at binder_open() instead of looking up the euid from the binder proc's 'struct task'. This ensures the euid is associated with the security context that of the task that opened binder. Cc: stable@vger.kernel.org # 4.4+ Fixes: 457b9a6f09f0 ("Staging: android: add binder driver") Signed-off-by: Todd Kjos Suggested-by: Stephen Smalley Suggested-by: Jann Horn Acked-by: Casey Schaufler Signed-off-by: Paul Moore Change-Id: I91922e7f359df5901749f1b09094c3c68d45aed4 --- drivers/android/binder.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 65b22b5af51a..4e33f6e42ac4 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -420,6 +420,9 @@ enum binder_deferred_state { * (invariant after initialized) * @tsk task_struct for group_leader of process * (invariant after initialized) + * @cred struct cred associated with the `struct file` + * in binder_open() + * (invariant after initialized) * @deferred_work_node: element for binder_deferred_list * (protected by binder_deferred_lock) * @deferred_work: bitmap of deferred work to perform @@ -465,6 +468,7 @@ struct binder_proc { struct list_head waiting_threads; int pid; struct task_struct *tsk; + const struct cred *cred; struct hlist_node deferred_work_node; int deferred_work; bool is_dead; @@ -3088,7 +3092,7 @@ static void binder_transaction(struct binder_proc *proc, t->from = thread; else t->from = NULL; - t->sender_euid = task_euid(proc->tsk); + t->sender_euid = proc->cred->euid; t->to_proc = target_proc; t->to_thread = target_thread; t->code = tr->code; @@ -4703,6 +4707,7 @@ static void binder_free_proc(struct binder_proc *proc) } binder_alloc_deferred_release(&proc->alloc); put_task_struct(proc->tsk); + put_cred(proc->cred); binder_stats_deleted(BINDER_STAT_PROC); kfree(proc); } @@ -5220,6 +5225,7 @@ static int binder_open(struct inode *nodp, struct file *filp) spin_lock_init(&proc->outer_lock); get_task_struct(current->group_leader); proc->tsk = current->group_leader; + proc->cred = get_cred(filp->f_cred); INIT_LIST_HEAD(&proc->todo); proc->default_priority = task_nice(current); /* binderfs stashes devices in i_private */