From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vasily Khoruzhick Subject: Re: [PATCH v3] pxa2xx_spi: fix memory corruption Date: Mon, 18 Jul 2011 10:56:51 +0300 Message-ID: <201107181056.51782.anarsoul@gmail.com> References: <201107101609.31405.anarsoul@gmail.com> <1310311099-24638-1-git-send-email-anarsoul@gmail.com> <20110715025331.GL2927@ponder.secretlab.ca> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: David Brownell , Russell King - ARM Linux , Marek Vasut , spi-devel-general@lists.sourceforge.net, Eric Miao , linux-arm-kernel@lists.infradead.org To: Grant Likely Return-path: In-Reply-To: <20110715025331.GL2927@ponder.secretlab.ca> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org List-Id: linux-spi.vger.kernel.org On Friday 15 July 2011 05:53:31 Grant Likely wrote: > On Sun, Jul 10, 2011 at 06:18:19PM +0300, Vasily Khoruzhick wrote: > > pxa2xx_spi_probe allocates struct driver_data and null_dma_buf > > at same time via spi_alloc_master(), but then calculates > > null_dma_buf pointer incorrectly, and it causes memory corruption > > later if DMA usage is enabled. > > > > Signed-off-by: Vasily Khoruzhick > > --- > > v2: - add u8 __null_dma_buf[16] to the end of driver_data structure > > > > and use it as null_dma_buf after alignment. > > - use PTR_ALIGN instead of ALIGN > > > > v3: - drop (u8 *) cast, use & operator instead, change array name > > > > drivers/spi/pxa2xx_spi.c | 9 +++++---- > > 1 files changed, 5 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c > > index dc25bee..b25fe27 100644 > > --- a/drivers/spi/pxa2xx_spi.c > > +++ b/drivers/spi/pxa2xx_spi.c > > @@ -106,6 +106,7 @@ struct driver_data { > > > > int rx_channel; > > int tx_channel; > > u32 *null_dma_buf; > > > > + u8 null_dma_buf_unaligned[16]; > > Don't dma buffers need to be cache-line aligned? No, on PXA2xx they need to be 8-bytes aligned (according to PXA27x developer's manual) > How large is the actual transfer? Looks like 8 bytes, but I'm not sure, I'm not author of driver and did not dig deeply into its code. Just attempting to fix memory corruption. > Using the __aligned() or __cacheline_aligned > attribute is the correct way to make sure you've got a data buffer > that can be used for DMA mixed with other stuff. Then you don't need > to fool around with PTR_ALIGN or anything. Errr, it can't be applied to struct field, right? But driver needs per-device null_dma_buf (there's 3 SPI controllers on PXA2xx) > g. Regards Vasily