From 8ac3b6ee7c9ff2df7c99624bb1235e2e55623825 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Thu, 16 Dec 2021 08:24:08 +0100 Subject: [PATCH] xen/blkfront: harden blkfront against event channel storms commit 0fd08a34e8e3b67ec9bd8287ac0facf8374b844a upstream. The Xen blkfront driver is still vulnerable for an attack via excessive number of events sent by the backend. Fix that by using lateeoi event channels. This is part of XSA-391 Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich Signed-off-by: Greg Kroah-Hartman --- drivers/block/xen-blkfront.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c index ff7b62597b525..22842d2938c28 100644 --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -1573,9 +1573,12 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) unsigned long flags; struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)dev_id; struct blkfront_info *info = rinfo->dev_info; + unsigned int eoiflag = XEN_EOI_FLAG_SPURIOUS; - if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) + if (unlikely(info->connected != BLKIF_STATE_CONNECTED)) { + xen_irq_lateeoi(irq, XEN_EOI_FLAG_SPURIOUS); return IRQ_HANDLED; + } spin_lock_irqsave(&rinfo->ring_lock, flags); again: @@ -1591,6 +1594,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) unsigned long id; unsigned int op; + eoiflag = 0; + RING_COPY_RESPONSE(&rinfo->ring, i, &bret); id = bret.id; @@ -1707,6 +1712,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) spin_unlock_irqrestore(&rinfo->ring_lock, flags); + xen_irq_lateeoi(irq, eoiflag); + return IRQ_HANDLED; err: @@ -1714,6 +1721,8 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id) spin_unlock_irqrestore(&rinfo->ring_lock, flags); + /* No EOI in order to avoid further interrupts. */ + pr_alert("%s disabled for further use\n", info->gd->disk_name); return IRQ_HANDLED; } @@ -1753,8 +1762,8 @@ static int setup_blkring(struct xenbus_device *dev, if (err) goto fail; - err = bind_evtchn_to_irqhandler(rinfo->evtchn, blkif_interrupt, 0, - "blkif", rinfo); + err = bind_evtchn_to_irqhandler_lateeoi(rinfo->evtchn, blkif_interrupt, + 0, "blkif", rinfo); if (err <= 0) { xenbus_dev_fatal(dev, err, "bind_evtchn_to_irqhandler failed");