From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751851AbdHPEsy (ORCPT ); Wed, 16 Aug 2017 00:48:54 -0400 Received: from mail-pg0-f47.google.com ([74.125.83.47]:38645 "EHLO mail-pg0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751445AbdHPEsx (ORCPT ); Wed, 16 Aug 2017 00:48:53 -0400 From: Todd Poynor To: Doug Gilbert , "James E.J. Bottomley" , "Martin K. Petersen" Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Hannes Reinecke , Todd Poynor Subject: [PATCH] sg: recheck MMAP_IO request length with lock held Date: Tue, 15 Aug 2017 21:48:43 -0700 Message-Id: <20170816044843.96697-1-toddpoynor@google.com> X-Mailer: git-send-email 2.14.1.480.gb18f417b89-goog Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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) { -- 2.14.1.480.gb18f417b89-goog