From patchwork Wed Apr 20 09:25:03 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Juergen Gross X-Patchwork-Id: 12819980 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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3C7E6C433F5 for ; Wed, 20 Apr 2022 09:25:24 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.309042.525065 (Exim 4.92) (envelope-from ) id 1nh6aG-0002zR-CI; Wed, 20 Apr 2022 09:25:12 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 309042.525065; Wed, 20 Apr 2022 09:25:12 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1nh6aG-0002yQ-4c; Wed, 20 Apr 2022 09:25:12 +0000 Received: by outflank-mailman (input) for mailman id 309042; Wed, 20 Apr 2022 09:25:10 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1nh6aE-0002RO-Ib for xen-devel@lists.xenproject.org; Wed, 20 Apr 2022 09:25:10 +0000 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id c47f453f-c08b-11ec-a405-831a346695d4; Wed, 20 Apr 2022 11:25:07 +0200 (CEST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 0434D1F752; Wed, 20 Apr 2022 09:25:07 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id BDDE413A30; Wed, 20 Apr 2022 09:25:06 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id mJcbLXLRX2J1EAAAMHmgww (envelope-from ); Wed, 20 Apr 2022 09:25:06 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: c47f453f-c08b-11ec-a405-831a346695d4 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1650446707; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=iAfNb+rzirjhSwl4ClW1FKJTnvu8cALY2TvN6HT931g=; b=ZQy+kpryquGdTyAVd7Fk4MNIeKP+LpZmDiZBt5LpHx/c4DmT/Fs1UZOcSNZb1v97Ec0kG4 0IIPWpejvrN/+Ez0IEXPa1FxYFgNClgZft+LDYvJwmwScbmFTcXj9kliJa22SAP7H6J/dw GqGeOF30KSlNvhnI2hior/hjkZsMtBs= From: Juergen Gross To: xen-devel@lists.xenproject.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Juergen Gross , Boris Ostrovsky , Stefano Stabellini , "James E.J. Bottomley" , "Martin K. Petersen" Subject: [PATCH 4/4] xen/scsifront: harden driver against malicious backend Date: Wed, 20 Apr 2022 11:25:03 +0200 Message-Id: <20220420092503.11123-5-jgross@suse.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220420092503.11123-1-jgross@suse.com> References: <20220420092503.11123-1-jgross@suse.com> MIME-Version: 1.0 Instead of relying on a well behaved PV scsi backend verify all meta data received from the backend and avoid multiple reads of the same data from the shared ring page. In case any illegal data from the backend is detected switch the PV device to a new "error" state and deactivate it for further use. Use the "lateeoi" variant for the event channel in order to avoid event storms blocking the guest. Signed-off-by: Juergen Gross --- drivers/scsi/xen-scsifront.c | 104 +++++++++++++++++++++++++---------- 1 file changed, 76 insertions(+), 28 deletions(-) diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c index 8511bfc62963..761c9c463ecd 100644 --- a/drivers/scsi/xen-scsifront.c +++ b/drivers/scsi/xen-scsifront.c @@ -83,6 +83,8 @@ struct vscsifrnt_shadow { uint16_t rqid; uint16_t ref_rqid; + bool inflight; + unsigned int nr_grants; /* number of grants in gref[] */ struct scsiif_request_segment *sg; /* scatter/gather elements */ struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE]; @@ -104,7 +106,11 @@ struct vscsifrnt_info { struct xenbus_device *dev; struct Scsi_Host *host; - int host_active; + enum { + STATE_INACTIVE, + STATE_ACTIVE, + STATE_ERROR + } host_active; unsigned int evtchn; unsigned int irq; @@ -217,6 +223,8 @@ static int scsifront_do_request(struct vscsifrnt_info *info, for (i = 0; i < (shadow->nr_segments & ~VSCSIIF_SG_GRANT); i++) ring_req->seg[i] = shadow->seg[i]; + shadow->inflight = true; + RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(ring, notify); if (notify) notify_remote_via_irq(info->irq); @@ -224,6 +232,13 @@ static int scsifront_do_request(struct vscsifrnt_info *info, return 0; } +static void scsifront_set_error(struct vscsifrnt_info *info, const char *msg) +{ + shost_printk(KERN_ERR, info->host, KBUILD_MODNAME "%s\n" + "Disabling device for further use\n", msg); + info->host_active = STATE_ERROR; +} + static void scsifront_gnttab_done(struct vscsifrnt_info *info, struct vscsifrnt_shadow *shadow) { @@ -234,9 +249,8 @@ static void scsifront_gnttab_done(struct vscsifrnt_info *info, for (i = 0; i < shadow->nr_grants; i++) { if (unlikely(!gnttab_try_end_foreign_access(shadow->gref[i]))) { - shost_printk(KERN_ALERT, info->host, KBUILD_MODNAME - "grant still in use by backend\n"); - BUG(); + scsifront_set_error(info, "grant still in use by backend"); + return; } } @@ -308,6 +322,8 @@ static void scsifront_cdb_cmd_done(struct vscsifrnt_info *info, BUG_ON(sc == NULL); scsifront_gnttab_done(info, shadow); + if (info->host_active == STATE_ERROR) + return; scsifront_put_rqid(info, id); set_host_byte(sc, scsifront_host_byte(ring_rsp->rslt)); @@ -348,9 +364,7 @@ static void scsifront_sync_cmd_done(struct vscsifrnt_info *info, scsifront_wake_up(info); return; default: - shost_printk(KERN_ERR, info->host, KBUILD_MODNAME - "bad reset state %d, possibly leaking %u\n", - shadow->rslt_reset, id); + scsifront_set_error(info, "bad reset state"); break; } spin_unlock_irqrestore(&info->shadow_lock, flags); @@ -361,28 +375,41 @@ static void scsifront_sync_cmd_done(struct vscsifrnt_info *info, static void scsifront_do_response(struct vscsifrnt_info *info, struct vscsiif_response *ring_rsp) { - if (WARN(ring_rsp->rqid >= VSCSIIF_MAX_REQS || - test_bit(ring_rsp->rqid, info->shadow_free_bitmap), - "illegal rqid %u returned by backend!\n", ring_rsp->rqid)) + struct vscsifrnt_shadow *shadow; + + if (ring_rsp->rqid >= VSCSIIF_MAX_REQS || + !info->shadow[ring_rsp->rqid]->inflight) { + scsifront_set_error(info, "illegal rqid returned by backend!"); return; + } + shadow = info->shadow[ring_rsp->rqid]; + shadow->inflight = false; - if (info->shadow[ring_rsp->rqid]->act == VSCSIIF_ACT_SCSI_CDB) + if (shadow->act == VSCSIIF_ACT_SCSI_CDB) scsifront_cdb_cmd_done(info, ring_rsp); else scsifront_sync_cmd_done(info, ring_rsp); } -static int scsifront_ring_drain(struct vscsifrnt_info *info) +static int scsifront_ring_drain(struct vscsifrnt_info *info, + unsigned int *eoiflag) { - struct vscsiif_response *ring_rsp; + struct vscsiif_response ring_rsp; RING_IDX i, rp; int more_to_do = 0; - rp = info->ring.sring->rsp_prod; - rmb(); /* ordering required respective to dom0 */ + rp = READ_ONCE(info->ring.sring->rsp_prod); + virt_rmb(); /* ordering required respective to backend */ + if (RING_RESPONSE_PROD_OVERFLOW(&info->ring, rp)) { + scsifront_set_error(info, "illegal number of responses"); + return 0; + } for (i = info->ring.rsp_cons; i != rp; i++) { - ring_rsp = RING_GET_RESPONSE(&info->ring, i); - scsifront_do_response(info, ring_rsp); + RING_COPY_RESPONSE(&info->ring, i, &ring_rsp); + scsifront_do_response(info, &ring_rsp); + if (info->host_active == STATE_ERROR) + return 0; + *eoiflag = 0; } info->ring.rsp_cons = i; @@ -395,14 +422,15 @@ static int scsifront_ring_drain(struct vscsifrnt_info *info) return more_to_do; } -static int scsifront_cmd_done(struct vscsifrnt_info *info) +static int scsifront_cmd_done(struct vscsifrnt_info *info, + unsigned int *eoiflag) { int more_to_do; unsigned long flags; spin_lock_irqsave(info->host->host_lock, flags); - more_to_do = scsifront_ring_drain(info); + more_to_do = scsifront_ring_drain(info, eoiflag); info->wait_ring_available = 0; @@ -416,20 +444,28 @@ static int scsifront_cmd_done(struct vscsifrnt_info *info) static irqreturn_t scsifront_irq_fn(int irq, void *dev_id) { struct vscsifrnt_info *info = dev_id; + unsigned int eoiflag = XEN_EOI_FLAG_SPURIOUS; + + if (info->host_active == STATE_ERROR) { + xen_irq_lateeoi(irq, XEN_EOI_FLAG_SPURIOUS); + return IRQ_HANDLED; + } - while (scsifront_cmd_done(info)) + while (scsifront_cmd_done(info, &eoiflag)) /* Yield point for this unbounded loop. */ cond_resched(); + xen_irq_lateeoi(irq, eoiflag); + return IRQ_HANDLED; } static void scsifront_finish_all(struct vscsifrnt_info *info) { - unsigned i; + unsigned int i, dummy; struct vscsiif_response resp; - scsifront_ring_drain(info); + scsifront_ring_drain(info, &dummy); for (i = 0; i < VSCSIIF_MAX_REQS; i++) { if (test_bit(i, info->shadow_free_bitmap)) @@ -586,6 +622,9 @@ static int scsifront_queuecommand(struct Scsi_Host *shost, unsigned long flags; int err; + if (info->host_active == STATE_ERROR) + return SCSI_MLQUEUE_HOST_BUSY; + sc->result = 0; shadow->sc = sc; @@ -638,6 +677,9 @@ static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act) struct vscsifrnt_shadow *shadow, *s = scsi_cmd_priv(sc); int err = 0; + if (info->host_active == STATE_ERROR) + return FAILED; + shadow = kzalloc(sizeof(*shadow), GFP_NOIO); if (!shadow) return FAILED; @@ -709,6 +751,9 @@ static int scsifront_sdev_configure(struct scsi_device *sdev) struct vscsifrnt_info *info = shost_priv(sdev->host); int err; + if (info->host_active == STATE_ERROR) + return -EIO; + if (info && current == info->curr) { err = xenbus_printf(XBT_NIL, info->dev->nodename, info->dev_state_path, "%d", XenbusStateConnected); @@ -784,7 +829,7 @@ static int scsifront_alloc_ring(struct vscsifrnt_info *info) goto free_gnttab; } - err = bind_evtchn_to_irq(info->evtchn); + err = bind_evtchn_to_irq_lateeoi(info->evtchn); if (err <= 0) { xenbus_dev_fatal(dev, err, "bind_evtchn_to_irq"); goto free_gnttab; @@ -914,7 +959,7 @@ static int scsifront_probe(struct xenbus_device *dev, goto free_sring; } info->host = host; - info->host_active = 1; + info->host_active = STATE_ACTIVE; xenbus_switch_state(dev, XenbusStateInitialised); @@ -982,10 +1027,10 @@ static int scsifront_remove(struct xenbus_device *dev) pr_debug("%s: %s removed\n", __func__, dev->nodename); mutex_lock(&scsifront_mutex); - if (info->host_active) { + if (info->host_active != STATE_INACTIVE) { /* Scsi_host not yet removed */ scsi_remove_host(info->host); - info->host_active = 0; + info->host_active = STATE_INACTIVE; } mutex_unlock(&scsifront_mutex); @@ -1009,9 +1054,9 @@ static void scsifront_disconnect(struct vscsifrnt_info *info) */ mutex_lock(&scsifront_mutex); - if (info->host_active) { + if (info->host_active != STATE_INACTIVE) { scsi_remove_host(host); - info->host_active = 0; + info->host_active = STATE_INACTIVE; } mutex_unlock(&scsifront_mutex); @@ -1029,6 +1074,9 @@ static void scsifront_do_lun_hotplug(struct vscsifrnt_info *info, int op) unsigned int hst, chn, tgt, lun; struct scsi_device *sdev; + if (info->host_active == STATE_ERROR) + return; + dir = xenbus_directory(XBT_NIL, dev->otherend, "vscsi-devs", &dir_n); if (IS_ERR(dir)) return;