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 3335FC433EF for ; Wed, 22 Jun 2022 13:21:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232954AbiFVNVc (ORCPT ); Wed, 22 Jun 2022 09:21:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349975AbiFVNV1 (ORCPT ); Wed, 22 Jun 2022 09:21:27 -0400 X-Greylist: delayed 521 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Wed, 22 Jun 2022 06:21:24 PDT Received: from mail.turbocat.net (turbocat.net [IPv6:2a01:4f8:c17:6c4b::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 825AF3122C; Wed, 22 Jun 2022 06:21:24 -0700 (PDT) Received: from [10.36.2.165] (unknown [178.232.223.95]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.turbocat.net (Postfix) with ESMTPSA id B9F7726021A; Wed, 22 Jun 2022 15:12:38 +0200 (CEST) Message-ID: <4883f0a7-6a1b-31bd-33fe-db8f6dcf73fa@selasky.org> Date: Wed, 22 Jun 2022 15:12:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH] media: dvb_ringbuffer : Fix a bug in dvb_ringbuffer.c Content-Language: en-US To: Kieran Bingham , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, mchehab@kernel.org, =?UTF-8?B?7Jyg7Jqp7IiY?= References: <165590120140.1149771.2257818527859865760@Monstersaurus> From: Hans Petter Selasky In-Reply-To: <165590120140.1149771.2257818527859865760@Monstersaurus> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Kieran, The consumed variable should not be negative. This bug has been there since the beginning of the GIT at Linux from what I can see. +1 --HPS From 108c6acb2cc4bc4314b96f6f254a04b2873a096c Mon Sep 17 00:00:00 2001 From: YongSu Yoo Date: Sun, 22 May 2022 04:53:12 +0000 Subject: [PATCH] media: dvb_ringbuffer : Fix a bug in dvb_ringbuffer.c Signed-off-by:Yongsu Yoo The function dvb_ringbuffer_pkt_next in /linux-next/drviers/media/dvb-core/dvb_ringbuffer.c, which searches the idx of the next valid packet in the ring buffer of the ca->slot_info[slot].rx_buffer at /linux-next/drivers/media/dvb-core/dvb_ca_en50221.c, has the following problem. In calculating the amounts of the consumed address of the ring buffer, if the read address(rbuf->pread) of the ring buffer is smaller than the idx, the amounts of the searched address should be (idx - rbuf->pread), whereas if the read address(rbuf->pread) of the ring buffer is larger than the idx, the amounts of the consumed address should be (idx - rbuf->pread + rbug->size). But there exists an incorrect logic that the rbug-size was not properly added on (idx - rbug->pread) in the later case. With this commit, we fixed this bug. --- drivers/media/dvb-core/dvb_ringbuffer.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/media/dvb-core/dvb_ringbuffer.c b/drivers/media/dvb-core/dvb_ringbuffer.c index d1d471af0636..7d4558de8e83 100644 --- a/drivers/media/dvb-core/dvb_ringbuffer.c +++ b/drivers/media/dvb-core/dvb_ringbuffer.c @@ -335,7 +335,9 @@ ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf, size_t idx, size_t* idx = (idx + curpktlen + DVB_RINGBUFFER_PKTHDRSIZE) % rbuf->size; } - consumed = (idx - rbuf->pread) % rbuf->size; + consumed = (idx - rbuf->pread); + if (consumed < 0) + consumed += rbuf->size; while((dvb_ringbuffer_avail(rbuf) - consumed) > DVB_RINGBUFFER_PKTHDRSIZE) { -- 2.17.1