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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E3ACC433F5 for ; Mon, 3 Jan 2022 14:39:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235216AbiACOjH (ORCPT ); Mon, 3 Jan 2022 09:39:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41386 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234753AbiACOhR (ORCPT ); Mon, 3 Jan 2022 09:37:17 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69903C08EAE8; Mon, 3 Jan 2022 06:33:46 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 09EAE6111C; Mon, 3 Jan 2022 14:33:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3E24C36AED; Mon, 3 Jan 2022 14:33:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1641220425; bh=2Vf+g/bkIufE5USblplqghA06QdAoPDr3Ofbc/AYPKo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YPbyDQ275X3LD7WQa8swqsrWHrmc/8a9E7ziUGtjXbmdhZgcFdxRBGPwhB/OxZz1H haEMObHKJZUk5f3/EW8NHgl8A7B1jhSOwjKUgUiodIsAjNG53JOzqMS4aC8mdxsKhv NE9eIbucNlAw397OFtnCdrSxWKewgkoI+BYLSGUc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Todd Kjos Subject: [PATCH 5.15 64/73] binder: fix async_free_space accounting for empty parcels Date: Mon, 3 Jan 2022 15:24:25 +0100 Message-Id: <20220103142058.994364491@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220103142056.911344037@linuxfoundation.org> References: <20220103142056.911344037@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 cfd0d84ba28c18b531648c9d4a35ecca89ad9901 upstream. In 4.13, commit 74310e06be4d ("android: binder: Move buffer out of area shared with user space") fixed a kernel structure visibility issue. As part of that patch, sizeof(void *) was used as the buffer size for 0-length data payloads so the driver could detect abusive clients sending 0-length asynchronous transactions to a server by enforcing limits on async_free_size. Unfortunately, on the "free" side, the accounting of async_free_space did not add the sizeof(void *) back. The result was that up to 8-bytes of async_free_space were leaked on every async transaction of 8-bytes or less. These small transactions are uncommon, so this accounting issue has gone undetected for several years. The fix is to use "buffer_size" (the allocated buffer size) instead of "size" (the logical buffer size) when updating the async_free_space during the free operation. These are the same except for this corner case of asynchronous transactions with payloads < 8 bytes. Fixes: 74310e06be4d ("android: binder: Move buffer out of area shared with user space") Signed-off-by: Todd Kjos Cc: stable@vger.kernel.org # 4.14+ Link: https://lore.kernel.org/r/20211220190150.2107077-1-tkjos@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -671,7 +671,7 @@ static void binder_free_buf_locked(struc BUG_ON(buffer->user_data > alloc->buffer + alloc->buffer_size); if (buffer->async_transaction) { - alloc->free_async_space += size + sizeof(struct binder_buffer); + alloc->free_async_space += buffer_size + sizeof(struct binder_buffer); binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC_ASYNC, "%d: binder_free_buf size %zd async free %zd\n",