From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752822AbdHVVhS (ORCPT ); Tue, 22 Aug 2017 17:37:18 -0400 Received: from smtp.infotech.no ([82.134.31.41]:35724 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752019AbdHVVhR (ORCPT ); Tue, 22 Aug 2017 17:37:17 -0400 Reply-To: dgilbert@interlog.com Subject: Re: [PATCH] sg: recheck MMAP_IO request length with lock held To: Todd Poynor , "James E.J. Bottomley" , "Martin K. Petersen" Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Hannes Reinecke References: <20170816044843.96697-1-toddpoynor@google.com> From: Douglas Gilbert Message-ID: Date: Tue, 22 Aug 2017 17:37:10 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170816044843.96697-1-toddpoynor@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-CA Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017-08-16 12:48 AM, Todd Poynor wrote: > Commit 1bc0eb044615 ("scsi: sg: protect accesses to 'reserved' page > array") adds needed concurrency protection for the "reserve" buffer. > Some checks that are initially made outside the lock are replicated once > the lock is taken to ensure the checks and resulting decisions are made > using consistent state. > > The check that a request with flag SG_FLAG_MMAP_IO set fits in the > reserve buffer also needs to be performed again under the lock to > ensure the reserve buffer length compared against matches the value in > effect when the request is linked to the reserve buffer. An -ENOMEM > should be returned in this case, instead of switching over to an > indirect buffer as for non-MMAP_IO requests. > > Signed-off-by: Todd Poynor Acked-by: Douglas Gilbert Thanks. > --- > drivers/scsi/sg.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c > index d7ff71e0c85c..3a44b4bc872b 100644 > --- a/drivers/scsi/sg.c > +++ b/drivers/scsi/sg.c > @@ -1735,9 +1735,12 @@ sg_start_req(Sg_request *srp, unsigned char *cmd) > !sfp->res_in_use) { > sfp->res_in_use = 1; > sg_link_reserve(sfp, srp, dxfer_len); > - } else if ((hp->flags & SG_FLAG_MMAP_IO) && sfp->res_in_use) { > + } else if (hp->flags & SG_FLAG_MMAP_IO) { > + res = -EBUSY; /* sfp->res_in_use == 1 */ > + if (dxfer_len > rsv_schp->bufflen) > + res = -ENOMEM; > mutex_unlock(&sfp->f_mutex); > - return -EBUSY; > + return res; > } else { > res = sg_build_indirect(req_schp, sfp, dxfer_len); > if (res) { >