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(-)
--- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -1555,9 +1555,12 @@ static irqreturn_t blkif_interrupt(int i struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)dev_id; struct blkfront_info *info = rinfo->dev_info; int error; + 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: @@ -1573,6 +1576,8 @@ 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;
@@ -1684,6 +1689,8 @@ static irqreturn_t blkif_interrupt(int i
spin_unlock_irqrestore(&rinfo->ring_lock, flags);
+ xen_irq_lateeoi(irq, eoiflag); + return IRQ_HANDLED;
err: @@ -1691,6 +1698,8 @@ 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; } @@ -1730,8 +1739,8 @@ 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");