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 X-Spam-Level: X-Spam-Status: No, score=-7.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06681C67838 for ; Thu, 6 Dec 2018 14:54:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BEEBE20850 for ; Thu, 6 Dec 2018 14:54:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544108067; bh=n14lwEW6eQtcGZgGPAiuOCYwMTpb0Yd+oEo2Cr5Es7U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=2sToYDxtHLeaX4v8hXNr1weFWZXe9s2opJnADKn4oYvBu5GM0UObPghTyb+aAWGnc 7D7CCywLIS5IrTmmRjfXGbkX91sFundKt1sM9ZerQjhlV2EAjSIoAoy+qr2wSSdtYU sg9lJfQP7M9v/s1cP4otMF0I5qrnsdvycG1l/RP8= DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BEEBE20850 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727017AbeLFOy0 (ORCPT ); Thu, 6 Dec 2018 09:54:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:49534 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730926AbeLFOou (ORCPT ); Thu, 6 Dec 2018 09:44:50 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2606C2082B; Thu, 6 Dec 2018 14:44:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1544107489; bh=n14lwEW6eQtcGZgGPAiuOCYwMTpb0Yd+oEo2Cr5Es7U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cmRU6Bka2Z7laTeHveIPb9g0YPloETYZoOz2B6U2bw9wfk6C+tkGzPw18WpiRQNuv 1jnIXesUT2pq1ClyHnnqs/rqTwKAv9it5WIq0X4H0r3wlCAHKxKIbXoCLeRs6wCJn3 M89pI1z9UUWGIlP3BlQxBzuaXYlvU0wej330sTxs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Todd Kjos Subject: [PATCH 4.9 025/101] binder: fix proc->files use-after-free Date: Thu, 6 Dec 2018 15:38:24 +0100 Message-Id: <20181206143013.033685511@linuxfoundation.org> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20181206143011.174892052@linuxfoundation.org> References: <20181206143011.174892052@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Todd Kjos commit 7f3dc0088b98533f17128058fac73cd8b2752ef1 upstream. proc->files cleanup is initiated by binder_vma_close. Therefore a reference on the binder_proc is not enough to prevent the files_struct from being released while the binder_proc still has a reference. This can lead to an attempt to dereference the stale pointer obtained from proc->files prior to proc->files cleanup. This has been seen once in task_get_unused_fd_flags() when __alloc_fd() is called with a stale "files". The fix is to protect proc->files with a mutex to prevent cleanup while in use. Signed-off-by: Todd Kjos Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder.c | 41 +++++++++++++++++++++++++++++------------ 1 file changed, 29 insertions(+), 12 deletions(-) --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -302,6 +302,7 @@ struct binder_proc { struct mm_struct *vma_vm_mm; struct task_struct *tsk; struct files_struct *files; + struct mutex files_lock; struct hlist_node deferred_work_node; int deferred_work; void *buffer; @@ -375,20 +376,26 @@ binder_defer_work(struct binder_proc *pr static int task_get_unused_fd_flags(struct binder_proc *proc, int flags) { - struct files_struct *files = proc->files; unsigned long rlim_cur; unsigned long irqs; + int ret; - if (files == NULL) - return -ESRCH; - - if (!lock_task_sighand(proc->tsk, &irqs)) - return -EMFILE; - + mutex_lock(&proc->files_lock); + if (proc->files == NULL) { + ret = -ESRCH; + goto err; + } + if (!lock_task_sighand(proc->tsk, &irqs)) { + ret = -EMFILE; + goto err; + } rlim_cur = task_rlimit(proc->tsk, RLIMIT_NOFILE); unlock_task_sighand(proc->tsk, &irqs); - return __alloc_fd(files, 0, rlim_cur, flags); + ret = __alloc_fd(proc->files, 0, rlim_cur, flags); +err: + mutex_unlock(&proc->files_lock); + return ret; } /* @@ -397,8 +404,10 @@ static int task_get_unused_fd_flags(stru static void task_fd_install( struct binder_proc *proc, unsigned int fd, struct file *file) { + mutex_lock(&proc->files_lock); if (proc->files) __fd_install(proc->files, fd, file); + mutex_unlock(&proc->files_lock); } /* @@ -408,9 +417,11 @@ static long task_close_fd(struct binder_ { int retval; - if (proc->files == NULL) - return -ESRCH; - + mutex_lock(&proc->files_lock); + if (proc->files == NULL) { + retval = -ESRCH; + goto err; + } retval = __close_fd(proc->files, fd); /* can't restart close syscall because file table entry was cleared */ if (unlikely(retval == -ERESTARTSYS || @@ -418,7 +429,8 @@ static long task_close_fd(struct binder_ retval == -ERESTARTNOHAND || retval == -ERESTART_RESTARTBLOCK)) retval = -EINTR; - +err: + mutex_unlock(&proc->files_lock); return retval; } @@ -2946,7 +2958,9 @@ static int binder_mmap(struct file *filp binder_insert_free_buffer(proc, buffer); proc->free_async_space = proc->buffer_size / 2; barrier(); + mutex_lock(&proc->files_lock); proc->files = get_files_struct(current); + mutex_unlock(&proc->files_lock); proc->vma = vma; proc->vma_vm_mm = vma->vm_mm; @@ -2982,6 +2996,7 @@ static int binder_open(struct inode *nod return -ENOMEM; get_task_struct(current->group_leader); proc->tsk = current->group_leader; + mutex_init(&proc->files_lock); INIT_LIST_HEAD(&proc->todo); init_waitqueue_head(&proc->wait); proc->default_priority = task_nice(current); @@ -3220,9 +3235,11 @@ static void binder_deferred_func(struct files = NULL; if (defer & BINDER_DEFERRED_PUT_FILES) { + mutex_lock(&proc->files_lock); files = proc->files; if (files) proc->files = NULL; + mutex_unlock(&proc->files_lock); } if (defer & BINDER_DEFERRED_FLUSH)