From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Cox Subject: Re: [PATCH] tty: Correct tty buffer flush. Date: Tue, 4 Dec 2012 14:12:23 +0000 Message-ID: <20121204141223.2ecb0f76@pyramind.ukuu.org.uk> References: <50BDF661.30303@ilyx.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <50BDF661.30303@ilyx.ru> Sender: linux-kernel-owner@vger.kernel.org To: Ilya Zykov Cc: Greg Kroah-Hartman , Alan Cox , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org List-Id: linux-serial@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