Apply XSA 270 fix

(cherry picked from commit ce8314b4e1)

patches.xen/xsa270.patch

@@ -0,0 +1,49 @@
+From: Jan Beulich <jbeulich@suse.com>
+Subject: xen-netback: fix input validation in xenvif_set_hash_mapping()
+
+Both len and off are frontend specified values, so we need to make
+sure there's no overflow when adding the two for the bounds check. We
+also want to avoid undefined behavior and hence use off to index into
+->hash.mapping[] only after bounds checking. This at the same time
+allows to take care of not applying off twice for the bounds checking
+against vif->num_queues.
+
+It is also insufficient to bounds check copy_op.len, as this is len
+truncated to 16 bits.
+
+This is XSA-270.
+
+Signed-off-by: Jan Beulich <jbeulich@suse.com>
+Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
+Tested-by: Paul Durrant <paul.durrant@citrix.com>
+
+--- a/drivers/net/xen-netback/hash.c
++++ b/drivers/net/xen-netback/hash.c
+@@ -332,20 +332,22 @@ u32 xenvif_set_hash_mapping_size(struct
+ u32 xenvif_set_hash_mapping(struct xenvif *vif, u32 gref, u32 len,
+ 			    u32 off)
+ {
+-	u32 *mapping = &vif->hash.mapping[off];
++	u32 *mapping = vif->hash.mapping;
+ 	struct gnttab_copy copy_op = {
+ 		.source.u.ref = gref,
+ 		.source.domid = vif->domid,
+-		.dest.u.gmfn = virt_to_gfn(mapping),
+ 		.dest.domid = DOMID_SELF,
+-		.dest.offset = xen_offset_in_page(mapping),
+-		.len = len * sizeof(u32),
++		.len = len * sizeof(*mapping),
+ 		.flags = GNTCOPY_source_gref
+ 	};
+ 
+-	if ((off + len > vif->hash.size) || copy_op.len > XEN_PAGE_SIZE)
++	if ((off + len < off) || (off + len > vif->hash.size) ||
++	    len > XEN_PAGE_SIZE / sizeof(*mapping))
+ 		return XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER;
+ 
++	copy_op.dest.u.gmfn = virt_to_gfn(mapping + off);
++	copy_op.dest.offset = xen_offset_in_page(mapping + off);
++
+ 	while (len-- != 0)
+ 		if (mapping[off++] >= vif->num_queues)
+ 			return XEN_NETIF_CTRL_STATUS_INVALID_PARAMETER;

series.conf

@@ -18,6 +18,7 @@ patches.xen/xsa155-linux44-0010-xen-netfront-do-not-use-data-already-exposed-to-
 patches.xen/xsa155-linux-0011-xen-netfront-add-range-check-for-Tx-response-id.patch
 patches.xen/xsa155-linux312-0012-xen-blkfront-make-local-copy-of-response-before-usin.patch
 patches.xen/xsa155-linux44-0013-xen-blkfront-prepare-request-locally-only-then-put-i.patch
+patches.xen/xsa270.patch
 
 # MSI-X enabled device passthrough fix (#1734)
 patches.xen/pci_op-cleanup.patch