Merge tag 'for-linus-5.12-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:
 "A series of Xen related security fixes, all related to limited error
  handling in Xen backend drivers"

* tag 'for-linus-5.12-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen-blkback: fix error handling in xen_blkbk_map()
  xen-scsiback: don't "handle" error by BUG()
  xen-netback: don't "handle" error by BUG()
  xen-blkback: don't "handle" error by BUG()
  xen/arm: don't ignore return errors from set_phys_to_machine
  Xen/gntdev: correct error checking in gntdev_map_grant_pages()
  Xen/gntdev: correct dev_bus_addr handling in gntdev_map_grant_pages()
  Xen/x86: also check kernel mapping in set_foreign_p2m_mapping()
  Xen/x86: don't bail early from clear_foreign_p2m_mapping()

1 files changed, 18 insertions, 14 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 9ebf53903d7b..da16121140ca 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -794,8 +794,13 @@ again:
 			pages[i]->persistent_gnt = persistent_gnt;
 		} else {
 			if (gnttab_page_cache_get(&ring->free_pages,
-						  &pages[i]->page))
-				goto out_of_memory;
+						  &pages[i]->page)) {
+				gnttab_page_cache_put(&ring->free_pages,
+						      pages_to_gnt,
+						      segs_to_map);
+				ret = -ENOMEM;
+				goto out;
+			}
 			addr = vaddr(pages[i]->page);
 			pages_to_gnt[segs_to_map] = pages[i]->page;
 			pages[i]->persistent_gnt = NULL;
@@ -811,10 +816,8 @@ again:
 			break;
 	}
 
-	if (segs_to_map) {
+	if (segs_to_map)
 		ret = gnttab_map_refs(map, NULL, pages_to_gnt, segs_to_map);
-		BUG_ON(ret);
-	}
 
 	/*
 	 * Now swizzle the MFN in our domain with the MFN from the other domain
@@ -830,7 +833,7 @@ again:
 				gnttab_page_cache_put(&ring->free_pages,
 						      &pages[seg_idx]->page, 1);
 				pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE;
-				ret |= 1;
+				ret |= !ret;
 				goto next;
 			}
 			pages[seg_idx]->handle = map[new_map_idx].handle;
@@ -882,17 +885,18 @@ next:
 	}
 	segs_to_map = 0;
 	last_map = map_until;
-	if (map_until != num)
+	if (!ret && map_until != num)
 		goto again;
 
-	return ret;
-
-out_of_memory:
-	pr_alert("%s: out of memory\n", __func__);
-	gnttab_page_cache_put(&ring->free_pages, pages_to_gnt, segs_to_map);
-	for (i = last_map; i < num; i++)
+out:
+	for (i = last_map; i < num; i++) {
+		/* Don't zap current batch's valid persistent grants. */
+		if(i >= last_map + segs_to_map)
+			pages[i]->persistent_gnt = NULL;
 		pages[i]->handle = BLKBACK_INVALID_HANDLE;
-	return -ENOMEM;
+	}
+
+	return ret;
 }
 
 static int xen_blkbk_map_seg(struct pending_req *pending_req)