From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754335Ab2LDOHQ (ORCPT ); Tue, 4 Dec 2012 09:07:16 -0500 Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:51928 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751090Ab2LDOHN (ORCPT ); Tue, 4 Dec 2012 09:07:13 -0500 Date: Tue, 4 Dec 2012 14:12:23 +0000 From: Alan Cox To: Ilya Zykov Cc: Greg Kroah-Hartman , Alan Cox , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Subject: Re: [PATCH] tty: Correct tty buffer flush. Message-ID: <20121204141223.2ecb0f76@pyramind.ukuu.org.uk> In-Reply-To: <50BDF661.30303@ilyx.ru> References: <50BDF661.30303@ilyx.ru> X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.8; x86_64-redhat-linux-gnu) Face: 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 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 04 Dec 2012 17:10:57 +0400 Ilya Zykov wrote: > The root of problem is carelessly zeroing pointer(in function __tty_buffer_flush()), > when another thread can use it. It can be cause of "NULL pointer dereference". > Main idea of the patch, this is never free last (struct tty_buffer) in the active buffer. > Only flush the data for ldisc(tty->buf.head->read = tty->buf.head->commit). > At that moment driver can collect(write) data in buffer without conflict. > It is repeat behavior of flush_to_ldisc(), only without feeding data to ldisc. > > Also revert: > commit c56a00a165712fd73081f40044b1e64407bb1875 > tty: hold lock across tty buffer finding and buffer filling > In order to delete the unneeded locks any more. > > Signed-off-by: Ilya Zykov Acked-by: Alan Cox