From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:44696 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936355AbeBUNLT (ORCPT ); Wed, 21 Feb 2018 08:11:19 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Rich Felker , Miklos Szeredi , Al Viro Subject: [PATCH 4.15 124/163] seq_file: fix incomplete reset on read from zero offset Date: Wed, 21 Feb 2018 13:49:13 +0100 Message-Id: <20180221124537.001351159@linuxfoundation.org> In-Reply-To: <20180221124529.931834518@linuxfoundation.org> References: <20180221124529.931834518@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Miklos Szeredi commit cf5eebae2cd28d37581507668605f4d23cd7218d upstream. When resetting iterator on a zero offset we need to discard any data already in the buffer (count), and private state of the iterator (version). For example this bug results in first line being repeated in /proc/mounts if doing a zero size read before a non-zero size read. Reported-by: Rich Felker Signed-off-by: Miklos Szeredi Fixes: e522751d605d ("seq_file: reset iterator to first record for zero offset") Cc: # v4.10 Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- fs/seq_file.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -181,8 +181,11 @@ ssize_t seq_read(struct file *file, char * if request is to read from zero offset, reset iterator to first * record as it might have been already advanced by previous requests */ - if (*ppos == 0) + if (*ppos == 0) { m->index = 0; + m->version = 0; + m->count = 0; + } /* Don't assume *ppos is where we left it */ if (unlikely(*ppos != m->read_pos)) {