From patchwork Mon Jun 27 18:31:44 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tony Battersby X-Patchwork-Id: 12896998 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9385BC433EF for ; Mon, 27 Jun 2022 18:40:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229688AbiF0Sk0 (ORCPT ); Mon, 27 Jun 2022 14:40:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240206AbiF0Sgb (ORCPT ); Mon, 27 Jun 2022 14:36:31 -0400 Received: from mail.cybernetics.com (mail.cybernetics.com [173.71.130.66]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E9BB18E16 for ; Mon, 27 Jun 2022 11:31:47 -0700 (PDT) X-ASG-Debug-ID: 1656354704-1cf43917f34b7230001-ziuLRu Received: from cybernetics.com ([10.10.4.126]) by mail.cybernetics.com with ESMTP id naijEmfSrSuv1xxb; Mon, 27 Jun 2022 14:31:44 -0400 (EDT) X-Barracuda-Envelope-From: tonyb@cybernetics.com X-ASG-Whitelist: Client DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=cybernetics.com; s=mail; bh=AZIOqz9a50o71eUeYVPVnDbfZ4G9lvqHTKKJssasw3I=; h=Content-Transfer-Encoding:Content-Type:Cc:Subject:From:To:Content-Language: MIME-Version:Date:Message-ID; b=SU5IiUYbKyhgGmCg3JZu8LqPRgiqv0EGiWV9hQxslwDAI vXs30bN5AFstLK5JjbPOmhtA7e6BZU4z5mkJCCUWi3HOMw2LtCRM3PyfygCEmt/z2/vXG5hUFDw66 WRSOvr00wz4Se6zieMK6+fbT2FfBQRSOoPzGIe0OHhMA/sfqg= Received: from [10.157.2.224] (HELO [192.168.200.1]) by cybernetics.com (CommuniGate Pro SMTP 7.1.1) with ESMTPS id 11973830; Mon, 27 Jun 2022 14:31:44 -0400 Message-ID: <2e713f6f-063d-0fcd-6fcc-05378aa8d08f@cybernetics.com> Date: Mon, 27 Jun 2022 14:31:44 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Content-Language: en-US To: Doug Gilbert , "James E.J. Bottomley" , "Martin K. Petersen" From: Tony Battersby Subject: [PATCH] sg: allow waiting for commands to complete on removed device Cc: linux-scsi@vger.kernel.org X-ASG-Orig-Subj: [PATCH] sg: allow waiting for commands to complete on removed device X-Barracuda-Connect: UNKNOWN[10.10.4.126] X-Barracuda-Start-Time: 1656354704 X-Barracuda-URL: https://10.10.4.122:443/cgi-mod/mark.cgi X-Barracuda-BRTS-Status: 1 X-Virus-Scanned: by bsmtpd at cybernetics.com X-Barracuda-Scan-Msg-Size: 5035 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org When a SCSI device is removed while in active use, currently sg will immediately return -ENODEV on any attempt to wait for active commands that were sent before the removal. This is problematic for commands that use SG_FLAG_DIRECT_IO since the data buffer may still be in use by the kernel when userspace frees or reuses it after getting ENODEV, leading to corrupted userspace memory (in the case of READ-type commands) or corrupted data being sent to the device (in the case of WRITE-type commands). This has been seen in practice when logging out of a iscsi_tcp session, where the iSCSI driver may still be processing commands after the device has been marked for removal. So change the policy to allow userspace to wait for active sg commands even when the device is being removed. Return -ENODEV only when there are no more responses to read. Cc: Signed-off-by: Tony Battersby --- drivers/scsi/sg.c | 53 +++++++++++++++++++++++++++++------------------ 1 file changed, 33 insertions(+), 20 deletions(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index 118c7b4a8af2..340b050ad28d 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -195,7 +195,7 @@ static void sg_link_reserve(Sg_fd * sfp, Sg_request * srp, int size); static void sg_unlink_reserve(Sg_fd * sfp, Sg_request * srp); static Sg_fd *sg_add_sfp(Sg_device * sdp); static void sg_remove_sfp(struct kref *); -static Sg_request *sg_get_rq_mark(Sg_fd * sfp, int pack_id); +static Sg_request *sg_get_rq_mark(Sg_fd * sfp, int pack_id, bool *busy); static Sg_request *sg_add_request(Sg_fd * sfp); static int sg_remove_request(Sg_fd * sfp, Sg_request * srp); static Sg_device *sg_get_dev(int dev); @@ -444,6 +444,7 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos) Sg_fd *sfp; Sg_request *srp; int req_pack_id = -1; + bool busy; sg_io_hdr_t *hp; struct sg_header *old_hdr; int retval; @@ -466,20 +467,16 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos) if (retval) return retval; - srp = sg_get_rq_mark(sfp, req_pack_id); + srp = sg_get_rq_mark(sfp, req_pack_id, &busy); if (!srp) { /* now wait on packet to arrive */ - if (atomic_read(&sdp->detaching)) - return -ENODEV; if (filp->f_flags & O_NONBLOCK) return -EAGAIN; retval = wait_event_interruptible(sfp->read_wait, - (atomic_read(&sdp->detaching) || - (srp = sg_get_rq_mark(sfp, req_pack_id)))); - if (atomic_read(&sdp->detaching)) - return -ENODEV; - if (retval) - /* -ERESTARTSYS as signal hit process */ - return retval; + ((srp = sg_get_rq_mark(sfp, req_pack_id, &busy)) || + (!busy && atomic_read(&sdp->detaching)))); + if (!srp) + /* signal or detaching */ + return retval ? retval : -ENODEV; } if (srp->header.interface_id != '\0') return sg_new_read(sfp, buf, count, srp); @@ -940,9 +937,7 @@ sg_ioctl_common(struct file *filp, Sg_device *sdp, Sg_fd *sfp, if (result < 0) return result; result = wait_event_interruptible(sfp->read_wait, - (srp_done(sfp, srp) || atomic_read(&sdp->detaching))); - if (atomic_read(&sdp->detaching)) - return -ENODEV; + srp_done(sfp, srp)); write_lock_irq(&sfp->rq_list_lock); if (srp->done) { srp->done = 2; @@ -2079,19 +2074,28 @@ sg_unlink_reserve(Sg_fd * sfp, Sg_request * srp) } static Sg_request * -sg_get_rq_mark(Sg_fd * sfp, int pack_id) +sg_get_rq_mark(Sg_fd * sfp, int pack_id, bool *busy) { Sg_request *resp; unsigned long iflags; + *busy = false; write_lock_irqsave(&sfp->rq_list_lock, iflags); list_for_each_entry(resp, &sfp->rq_list, entry) { - /* look for requests that are ready + not SG_IO owned */ - if ((1 == resp->done) && (!resp->sg_io_owned) && + /* look for requests that are not SG_IO owned */ + if ((!resp->sg_io_owned) && ((-1 == pack_id) || (resp->header.pack_id == pack_id))) { - resp->done = 2; /* guard against other readers */ - write_unlock_irqrestore(&sfp->rq_list_lock, iflags); - return resp; + switch (resp->done) { + case 0: /* request active */ + *busy = true; + break; + case 1: /* request done; response ready to return */ + resp->done = 2; /* guard against other readers */ + write_unlock_irqrestore(&sfp->rq_list_lock, iflags); + return resp; + case 2: /* response already being returned */ + break; + } } } write_unlock_irqrestore(&sfp->rq_list_lock, iflags); @@ -2145,6 +2149,15 @@ sg_remove_request(Sg_fd * sfp, Sg_request * srp) res = 1; } write_unlock_irqrestore(&sfp->rq_list_lock, iflags); + + /* + * If the device is detaching, wakeup any readers in case we just + * removed the last response, which would leave nothing for them to + * return other than -ENODEV. + */ + if (unlikely(atomic_read(&sfp->parentdp->detaching))) + wake_up_interruptible_all(&sfp->read_wait); + return res; }