diff mbox series

[4.19,52/56] xen/blkfront: harden blkfront against event channel storms

Message ID 20211220143025.178368697@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman Dec. 20, 2021, 2:34 p.m. UTC 
From: Juergen Gross <jgross@suse.com>

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 <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/block/xen-blkfront.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)
diff mbox series

Patch

--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1565,9 +1565,12 @@  static irqreturn_t blkif_interrupt(int i
 	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:
@@ -1583,6 +1586,8 @@  static irqreturn_t blkif_interrupt(int i
 		unsigned long id;
 		unsigned int op;
 
+		eoiflag = 0;
+
 		RING_COPY_RESPONSE(&rinfo->ring, i, &bret);
 		id = bret.id;
 
@@ -1698,6 +1703,8 @@  static irqreturn_t blkif_interrupt(int i
 
 	spin_unlock_irqrestore(&rinfo->ring_lock, flags);
 
+	xen_irq_lateeoi(irq, eoiflag);
+
 	return IRQ_HANDLED;
 
  err:
@@ -1705,6 +1712,8 @@  static irqreturn_t blkif_interrupt(int i
 
 	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;
 }
@@ -1744,8 +1753,8 @@  static int setup_blkring(struct xenbus_d
 	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");