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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no 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 EB817C433E0 for ; Thu, 4 Jun 2020 23:51:33 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AC2F820872 for ; Thu, 4 Jun 2020 23:51:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="bLlq3lwx" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC2F820872 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 4D5D5280067; Thu, 4 Jun 2020 19:51:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 45EC3280005; Thu, 4 Jun 2020 19:51:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 325AD280067; Thu, 4 Jun 2020 19:51:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0182.hostedemail.com [216.40.44.182]) by kanga.kvack.org (Postfix) with ESMTP id 18275280005 for ; Thu, 4 Jun 2020 19:51:33 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id DC50B824556B for ; Thu, 4 Jun 2020 23:51:32 +0000 (UTC) X-FDA: 76893178824.24.shelf85_2d0ea9026d9b Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id B38F91A4A0 for ; Thu, 4 Jun 2020 23:51:32 +0000 (UTC) X-HE-Tag: shelf85_2d0ea9026d9b X-Filterd-Recvd-Size: 4470 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Thu, 4 Jun 2020 23:51:32 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 408062067B; Thu, 4 Jun 2020 23:51:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591314691; bh=/jKX+RrCcD4abPwZtKcywloWP3DUdqaJuD7LgY0lWDk=; h=Date:From:To:Subject:In-Reply-To:From; b=bLlq3lwx032oIbCm9dbpnVNMdPke4hC7WypB30wPolWkCnzIeKsZod4q+QDcUfBIz VZtFdyszsPFTwgguZcTZY/tZiGZdFrhy6IAT5NK1awWoR15WcMeNEeWN5wcqJDE1Ot 83GQOuHZSnliDZV6WFza6PuxXrHd28SocxUGx9u8= Date: Thu, 04 Jun 2020 16:51:30 -0700 From: Andrew Morton To: akpm@linux-foundation.org, axboe@kernel.dk, gregkh@linuxfoundation.org, jannh@google.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, yangpc@wangsu.com Subject: [patch 101/127] kernel/relay.c: fix read_pos error when multiple readers Message-ID: <20200604235130.VLzTyFIRS%akpm@linux-foundation.org> In-Reply-To: <20200604164523.e15f3177f4b69dcb4f2534a1@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Queue-Id: B38F91A4A0 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Pengcheng Yang Subject: kernel/relay.c: fix read_pos error when multiple readers When reading, read_pos should start with bytes_consumed, not file->f_pos. Because when there is more than one reader, the read_pos corresponding to file->f_pos may have been consumed, which will cause the data that has been consumed to be read and the bytes_consumed update error. Link: http://lkml.kernel.org/r/1579691175-28949-1-git-send-email-yangpc@wangsu.com Signed-off-by: Pengcheng Yang Reviewed-by: Jens Axboe Cc: Greg Kroah-Hartman Cc: Jann Horn Cc: Al Viro e Signed-off-by: Andrew Morton --- kernel/relay.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) --- a/kernel/relay.c~kernel-relayc-fix-read_pos-error-when-multiple-readers +++ a/kernel/relay.c @@ -996,14 +996,14 @@ static void relay_file_read_consume(stru /* * relay_file_read_avail - boolean, are there unconsumed bytes available? */ -static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos) +static int relay_file_read_avail(struct rchan_buf *buf) { size_t subbuf_size = buf->chan->subbuf_size; size_t n_subbufs = buf->chan->n_subbufs; size_t produced = buf->subbufs_produced; size_t consumed = buf->subbufs_consumed; - relay_file_read_consume(buf, read_pos, 0); + relay_file_read_consume(buf, 0, 0); consumed = buf->subbufs_consumed; @@ -1064,23 +1064,20 @@ static size_t relay_file_read_subbuf_ava /** * relay_file_read_start_pos - find the first available byte to read - * @read_pos: file read position * @buf: relay channel buffer * - * If the @read_pos is in the middle of padding, return the + * If the read_pos is in the middle of padding, return the * position of the first actually available byte, otherwise * return the original value. */ -static size_t relay_file_read_start_pos(size_t read_pos, - struct rchan_buf *buf) +static size_t relay_file_read_start_pos(struct rchan_buf *buf) { size_t read_subbuf, padding, padding_start, padding_end; size_t subbuf_size = buf->chan->subbuf_size; size_t n_subbufs = buf->chan->n_subbufs; size_t consumed = buf->subbufs_consumed % n_subbufs; + size_t read_pos = consumed * subbuf_size + buf->bytes_consumed; - if (!read_pos) - read_pos = consumed * subbuf_size + buf->bytes_consumed; read_subbuf = read_pos / subbuf_size; padding = buf->padding[read_subbuf]; padding_start = (read_subbuf + 1) * subbuf_size - padding; @@ -1136,10 +1133,10 @@ static ssize_t relay_file_read(struct fi do { void *from; - if (!relay_file_read_avail(buf, *ppos)) + if (!relay_file_read_avail(buf)) break; - read_start = relay_file_read_start_pos(*ppos, buf); + read_start = relay_file_read_start_pos(buf); avail = relay_file_read_subbuf_avail(read_start, buf); if (!avail) break; _