Commit e61750c8 authored by Jens Axboe's avatar Jens Axboe
Browse files

Merge branch 'stable/for-jens-5.1' of...

Merge branch 'stable/for-jens-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen into for-5.1/block-post

Pull two xen blkback fixes from Konrad.

* 'stable/for-jens-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
  xen/blkback: rework connect_ring() to avoid inconsistent xenstore 'ring-page-order' set by malicious blkfront
  xen/blkback: add stack variable 'blkif' in connect_ring()
parents aaeee62c 4a8c31a1
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+57 −42
Original line number Diff line number Diff line
@@ -926,7 +926,7 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
	int err, i, j;
	struct xen_blkif *blkif = ring->blkif;
	struct xenbus_device *dev = blkif->be->dev;
	unsigned int ring_page_order, nr_grefs, evtchn;
	unsigned int nr_grefs, evtchn;

	err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
			  &evtchn);
@@ -936,43 +936,42 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
		return err;
	}

	err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u",
			  &ring_page_order);
	if (err != 1) {
		err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u", &ring_ref[0]);
		if (err != 1) {
			err = -EINVAL;
			xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
			return err;
		}
		nr_grefs = 1;
	} else {
		unsigned int i;
	nr_grefs = blkif->nr_ring_pages;

		if (ring_page_order > xen_blkif_max_ring_order) {
			err = -EINVAL;
			xenbus_dev_fatal(dev, err, "%s/request %d ring page order exceed max:%d",
					 dir, ring_page_order,
					 xen_blkif_max_ring_order);
			return err;
	if (unlikely(!nr_grefs)) {
		WARN_ON(true);
		return -EINVAL;
	}

		nr_grefs = 1 << ring_page_order;
	for (i = 0; i < nr_grefs; i++) {
		char ring_ref_name[RINGREF_NAME_LEN];

		snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
		err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
				   "%u", &ring_ref[i]);

		if (err != 1) {
			if (nr_grefs == 1)
				break;

			err = -EINVAL;
			xenbus_dev_fatal(dev, err, "reading %s/%s",
					 dir, ring_ref_name);
			return err;
		}
	}

	if (err != 1) {
		WARN_ON(nr_grefs != 1);

		err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u",
				   &ring_ref[0]);
		if (err != 1) {
			err = -EINVAL;
			xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
			return err;
		}
	}
	blkif->nr_ring_pages = nr_grefs;

	for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
		req = kzalloc(sizeof(*req), GFP_KERNEL);
@@ -1023,6 +1022,7 @@ fail:
static int connect_ring(struct backend_info *be)
{
	struct xenbus_device *dev = be->dev;
	struct xen_blkif *blkif = be->blkif;
	unsigned int pers_grants;
	char protocol[64] = "";
	int err, i;
@@ -1030,28 +1030,29 @@ static int connect_ring(struct backend_info *be)
	size_t xspathsize;
	const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
	unsigned int requested_num_queues = 0;
	unsigned int ring_page_order;

	pr_debug("%s %s\n", __func__, dev->otherend);

	be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
	blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
	err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
			   "%63s", protocol);
	if (err <= 0)
		strcpy(protocol, "unspecified, assuming default");
	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
		be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
		blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
		blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
	else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
		be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
		blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
	else {
		xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
		return -ENOSYS;
	}
	pers_grants = xenbus_read_unsigned(dev->otherend, "feature-persistent",
					   0);
	be->blkif->vbd.feature_gnt_persistent = pers_grants;
	be->blkif->vbd.overflow_max_grants = 0;
	blkif->vbd.feature_gnt_persistent = pers_grants;
	blkif->vbd.overflow_max_grants = 0;

	/*
	 * Read the number of hardware queues from frontend.
@@ -1067,16 +1068,30 @@ static int connect_ring(struct backend_info *be)
				requested_num_queues, xenblk_max_queues);
		return -ENOSYS;
	}
	be->blkif->nr_rings = requested_num_queues;
	if (xen_blkif_alloc_rings(be->blkif))
	blkif->nr_rings = requested_num_queues;
	if (xen_blkif_alloc_rings(blkif))
		return -ENOMEM;

	pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
		 be->blkif->nr_rings, be->blkif->blk_protocol, protocol,
		 blkif->nr_rings, blkif->blk_protocol, protocol,
		 pers_grants ? "persistent grants" : "");

	if (be->blkif->nr_rings == 1)
		return read_per_ring_refs(&be->blkif->rings[0], dev->otherend);
	ring_page_order = xenbus_read_unsigned(dev->otherend,
					       "ring-page-order", 0);

	if (ring_page_order > xen_blkif_max_ring_order) {
		err = -EINVAL;
		xenbus_dev_fatal(dev, err,
				 "requested ring page order %d exceed max:%d",
				 ring_page_order,
				 xen_blkif_max_ring_order);
		return err;
	}

	blkif->nr_ring_pages = 1 << ring_page_order;

	if (blkif->nr_rings == 1)
		return read_per_ring_refs(&blkif->rings[0], dev->otherend);
	else {
		xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
		xspath = kmalloc(xspathsize, GFP_KERNEL);
@@ -1085,10 +1100,10 @@ static int connect_ring(struct backend_info *be)
			return -ENOMEM;
		}

		for (i = 0; i < be->blkif->nr_rings; i++) {
		for (i = 0; i < blkif->nr_rings; i++) {
			memset(xspath, 0, xspathsize);
			snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
			err = read_per_ring_refs(&be->blkif->rings[i], xspath);
			err = read_per_ring_refs(&blkif->rings[i], xspath);
			if (err) {
				kfree(xspath);
				return err;