From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754430AbaCaAOt (ORCPT ); Sun, 30 Mar 2014 20:14:49 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:36396 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752695AbaC3XZC (ORCPT ); Sun, 30 Mar 2014 19:25:02 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Vinod Koul" , "Dan Carpenter" , "Linus Walleij" Date: Mon, 31 Mar 2014 00:23:35 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 120/200] dma: ste_dma40: don't dereference free:d descriptor In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.249 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.56-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Linus Walleij commit e9baa9d9d520fb0e24cca671e430689de2d4a4b2 upstream. It appears that in the DMA40 driver the DMA tasklet will very often dereference memory for a descriptor just free:d from the DMA40 slab. Nothing happens because no other part of the driver has yet had a chance to claim this memory, but it's really nasty to dereference free:d memory, so let's check the flag before the descriptor is free and store it in a bool variable. Reported-by: Dan Carpenter Signed-off-by: Linus Walleij Signed-off-by: Vinod Koul Signed-off-by: Ben Hutchings --- drivers/dma/ste_dma40.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/drivers/dma/ste_dma40.c +++ b/drivers/dma/ste_dma40.c @@ -1202,6 +1202,7 @@ static void dma_tasklet(unsigned long da struct d40_chan *d40c = (struct d40_chan *) data; struct d40_desc *d40d; unsigned long flags; + bool callback_active; dma_async_tx_callback callback; void *callback_param; @@ -1225,6 +1226,7 @@ static void dma_tasklet(unsigned long da } /* Callback to client */ + callback_active = !!(d40d->txd.flags & DMA_PREP_INTERRUPT); callback = d40d->txd.callback; callback_param = d40d->txd.callback_param; @@ -1249,7 +1251,7 @@ static void dma_tasklet(unsigned long da spin_unlock_irqrestore(&d40c->lock, flags); - if (callback && (d40d->txd.flags & DMA_PREP_INTERRUPT)) + if (callback_active && callback) callback(callback_param); return;