From mboxrd@z Thu Jan 1 00:00:00 1970 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 95084C4332F for ; Mon, 15 Nov 2021 17:12:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 80EF763256 for ; Mon, 15 Nov 2021 17:12:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236604AbhKORPF (ORCPT ); Mon, 15 Nov 2021 12:15:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:41208 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236418AbhKORLs (ORCPT ); Mon, 15 Nov 2021 12:11:48 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2BE8261BF4; Mon, 15 Nov 2021 17:08:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1636996132; bh=Yb1DRo3nYpan4Q6WGQKNsnhor4ILc5rjfzOK/hsewiw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R4H9FvSlXtdkmTWCNIgElbpbjBaezwTsVzZ9OmK92F9GPcaAzPuz+UE09n/6Lbsur PJLVJoWe222GeXkm7A453/pBR667uzF+6Wa4ze5+ke0iXNe0qTUADO8daRDm397hLR GKiWUUoeaYK6Sc0xB4y9lHO8jmPNUz0dH7fACBWg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Todd Kjos , Stephen Smalley , Jann Horn , Casey Schaufler , Paul Moore Subject: [PATCH 5.4 003/355] binder: use euid from cred instead of using task Date: Mon, 15 Nov 2021 17:58:47 +0100 Message-Id: <20211115165313.666212833@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211115165313.549179499@linuxfoundation.org> References: <20211115165313.549179499@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Todd Kjos 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 Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -424,6 +424,9 @@ 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 @@ -469,6 +472,7 @@ 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; @@ -3091,7 +3095,7 @@ static void binder_transaction(struct bi 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; @@ -4707,6 +4711,7 @@ static void binder_free_proc(struct bind } binder_alloc_deferred_release(&proc->alloc); put_task_struct(proc->tsk); + put_cred(proc->cred); binder_stats_deleted(BINDER_STAT_PROC); kfree(proc); } @@ -5234,6 +5239,7 @@ static int binder_open(struct inode *nod 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 */