From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932078AbaCYRV5 (ORCPT ); Tue, 25 Mar 2014 13:21:57 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55928 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755117AbaCYRVy (ORCPT ); Tue, 25 Mar 2014 13:21:54 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Linus Walleij , Vinod Koul , Kamal Mostafa Subject: [PATCH 3.8 49/81] dma: ste_dma40: don't dereference free:d descriptor Date: Tue, 25 Mar 2014 10:16:02 -0700 Message-Id: <1395767794-5012-50-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1395767794-5012-1-git-send-email-kamal@canonical.com> References: <1395767794-5012-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.8.13.20 -stable 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: Kamal Mostafa --- drivers/dma/ste_dma40.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c index 17459ad..da6426e 100644 --- a/drivers/dma/ste_dma40.c +++ b/drivers/dma/ste_dma40.c @@ -1410,6 +1410,7 @@ static void dma_tasklet(unsigned long data) 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; @@ -1433,6 +1434,7 @@ static void dma_tasklet(unsigned long data) } /* Callback to client */ + callback_active = !!(d40d->txd.flags & DMA_PREP_INTERRUPT); callback = d40d->txd.callback; callback_param = d40d->txd.callback_param; @@ -1457,7 +1459,7 @@ static void dma_tasklet(unsigned long data) spin_unlock_irqrestore(&d40c->lock, flags); - if (callback && (d40d->txd.flags & DMA_PREP_INTERRUPT)) + if (callback_active && callback) callback(callback_param); return; -- 1.8.3.2