From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [PATCH] libata: don't initialize sg in ata_exec_internal() if DMA_NONE Date: Mon, 11 Dec 2006 10:55:08 -0500 Message-ID: <457D7F5C.8040609@pobox.com> References: <200612081914.41810.arnd.bergmann@de.ibm.com> <20061211140258.GB18947@htj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:47036 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936815AbWLKPzR (ORCPT ); Mon, 11 Dec 2006 10:55:17 -0500 In-Reply-To: <20061211140258.GB18947@htj.dyndns.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: Arnd Bergmann , linux-ide@vger.kernel.org, linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org Tejun Heo wrote: > Calling sg_init_one() with NULL buf causes oops on certain > configurations. Don't initialize sg in ata_exec_internal() if > DMA_NONE and make the function complain if @buf is NULL when dma_dir > isn't DMA_NONE. While at it, fix comment. > > The problem is discovered and initial patch was submitted by Arnd > Bergmann. > > Signed-off-by: Tejun Heo > Cc: Arnd Bergmann > --- > > Hello, Arnd Bergmann. > > Thanks for spotting and fixing this but ata_exec_internal_nodma() is > almost identical to ata_do_simple_cmd() and ata_exec_internal() itself > needs fixing anyway. This patch just fixes ata_exec_internal(). I'll > follow up with conversion to ata_do_simple_cmd(). > > Thanks. > > diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c > index 011c0a8..70e02e9 100644 > --- a/drivers/ata/libata-core.c > +++ b/drivers/ata/libata-core.c > @@ -1332,7 +1332,7 @@ unsigned ata_exec_internal_sg(struct ata_device *dev, > } > > /** > - * ata_exec_internal_sg - execute libata internal command > + * ata_exec_internal - execute libata internal command > * @dev: Device to which the command is sent > * @tf: Taskfile registers for the command and the result > * @cdb: CDB for packet command > @@ -1354,10 +1354,15 @@ unsigned ata_exec_internal(struct ata_device *dev, > int dma_dir, void *buf, unsigned int buflen) > { > struct scatterlist sg; > + unsigned int n_elem = 0; > > - sg_init_one(&sg, buf, buflen); > + if (dma_dir != DMA_NONE) { > + WARN_ON(!buf); > + sg_init_one(&sg, buf, buflen); > + n_elem++; > + } > > - return ata_exec_internal_sg(dev, tf, cdb, dma_dir, &sg, 1); > + return ata_exec_internal_sg(dev, tf, cdb, dma_dir, &sg, n_elem); ACK, if you conditionally replace "&sg" with NULL. That's the safer choice, as it guarantees (via an oops) that the user will not be touching sg, if dma_dir==DMA_NONE. Jeff