From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH v2] libata-scsi: fix read-only bits checking in ata_mselect_*() Date: Wed, 20 Jul 2016 13:20:07 -0400 Message-ID: <20160720172007.GH4574@htj.duckdns.org> References: <578eaead.0198620a.7cf53.28c1@mx.google.com> <578eb0d1.e9b9420a.8694b.fc4c@mx.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-yw0-f196.google.com ([209.85.161.196]:34477 "EHLO mail-yw0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752583AbcGTRUK (ORCPT ); Wed, 20 Jul 2016 13:20:10 -0400 Content-Disposition: inline In-Reply-To: <578eb0d1.e9b9420a.8694b.fc4c@mx.google.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: tom.ty89@gmail.com Cc: hare@suse.de, linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org So, just reverted this patch. On Wed, Jul 20, 2016 at 06:59:23AM +0800, tom.ty89@gmail.com wrote: > From: Tom Yan > > Commit 7780081c1f04 ("libata-scsi: Set information sense field for > invalid parameter") changed how ata_mselect_*() make sure read-only > bits are not modified. The new implementation introduced a bug that > the read-only bits in the byte that has a changeable bit will not > be checked. > > Added the necessary check, with comments explaining the heuristic. > > Signed-off-by: Tom Yan > > diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c > index 06afe63..b47c3ce 100644 > --- a/drivers/ata/libata-scsi.c > +++ b/drivers/ata/libata-scsi.c > @@ -3617,8 +3617,18 @@ static int ata_mselect_caching(struct ata_queued_cmd *qc, > */ > ata_msense_caching(dev->id, mpage, false); > for (i = 0; i < CACHE_MPAGE_LEN - 2; i++) { > - if (i == 0) > - continue; > + /* Check the first byte */ > + if (i == 0) { > + /* except the WCE bit */ > + if (mpage[i + 2] & 0xfb != buf[i] & 0xfb) { This not only triggered compiler warning but is actually wrong. The above is mpage[i + 1] & (0xfb != buf[i]) & 0xfb which is non-sensical. So, this patch wasn't tested at all. Not even compile test. Please don't do this. Thanks. -- tejun