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()

7 files changed, 53 insertions, 46 deletions

diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c
index e52950a43f2e..fd6e3aafe272 100644
--- a/arch/arm/xen/p2m.c
+++ b/arch/arm/xen/p2m.c
@@ -95,8 +95,10 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 	for (i = 0; i < count; i++) {
 		if (map_ops[i].status)
 			continue;
-		set_phys_to_machine(map_ops[i].host_addr >> XEN_PAGE_SHIFT,
-				    map_ops[i].dev_bus_addr >> XEN_PAGE_SHIFT);
+		if (unlikely(!set_phys_to_machine(map_ops[i].host_addr >> XEN_PAGE_SHIFT,
+				    map_ops[i].dev_bus_addr >> XEN_PAGE_SHIFT))) {
+			return -ENOMEM;
+		}
 	}
 
 	return 0;
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 3301875dd196..b5949e5a83ec 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -712,7 +712,8 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref *map_ops,
 		unsigned long mfn, pfn;
 
 		/* Do not add to override if the map failed. */
-		if (map_ops[i].status)
+		if (map_ops[i].status != GNTST_okay ||
+		    (kmap_ops && kmap_ops[i].status != GNTST_okay))
 			continue;
 
 		if (map_ops[i].flags & GNTMAP_contains_pte) {
@@ -750,17 +751,15 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
 		unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
 		unsigned long pfn = page_to_pfn(pages[i]);
 
-		if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) {
+		if (mfn != INVALID_P2M_ENTRY && (mfn & FOREIGN_FRAME_BIT))
+			set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+		else
 			ret = -EINVAL;
-			goto out;
-		}
-
-		set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 	}
 	if (kunmap_ops)
 		ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
-						kunmap_ops, count);
-out:
+						kunmap_ops, count) ?: ret;
+
 	return ret;
 }
 EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);
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)
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 19a27dce79d2..e5c73f819662 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1343,13 +1343,11 @@ int xenvif_tx_action(struct xenvif_queue *queue, int budget)
 		return 0;
 
 	gnttab_batch_copy(queue->tx_copy_ops, nr_cops);
-	if (nr_mops != 0) {
+	if (nr_mops != 0)
 		ret = gnttab_map_refs(queue->tx_map_ops,
 				      NULL,
 				      queue->pages_to_map,
 				      nr_mops);
-		BUG_ON(ret);
-	}
 
 	work_done = xenvif_tx_submit(queue);
 
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index a36b71286bcf..5447c5156b2e 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -309,44 +309,47 @@ int gntdev_map_grant_pages(struct gntdev_grant_map *map)
 		 * to the kernel linear addresses of the struct pages.
 		 * These ptes are completely different from the user ptes dealt
 		 * with find_grant_ptes.
+		 * Note that GNTMAP_device_map isn't needed here: The
+		 * dev_bus_addr output field gets consumed only from ->map_ops,
+		 * and by not requesting it when mapping we also avoid needing
+		 * to mirror dev_bus_addr into ->unmap_ops (and holding an extra
+		 * reference to the page in the hypervisor).
 		 */
+		unsigned int flags = (map->flags & ~GNTMAP_device_map) |
+				     GNTMAP_host_map;
+
 		for (i = 0; i < map->count; i++) {
 			unsigned long address = (unsigned long)
 				pfn_to_kaddr(page_to_pfn(map->pages[i]));
 			BUG_ON(PageHighMem(map->pages[i]));
 
-			gnttab_set_map_op(&map->kmap_ops[i], address,
-				map->flags | GNTMAP_host_map,
+			gnttab_set_map_op(&map->kmap_ops[i], address, flags,
 				map->grants[i].ref,
 				map->grants[i].domid);
 			gnttab_set_unmap_op(&map->kunmap_ops[i], address,
-				map->flags | GNTMAP_host_map, -1);
+				flags, -1);
 		}
 	}
 
 	pr_debug("map %d+%d\n", map->index, map->count);
 	err = gnttab_map_refs(map->map_ops, use_ptemod ? map->kmap_ops : NULL,
 			map->pages, map->count);
-	if (err)
-		return err;
 
 	for (i = 0; i < map->count; i++) {
-		if (map->map_ops[i].status) {
+		if (map->map_ops[i].status == GNTST_okay)
+			map->unmap_ops[i].handle = map->map_ops[i].handle;
+		else if (!err)
 			err = -EINVAL;
-			continue;
-		}
 
-		map->unmap_ops[i].handle = map->map_ops[i].handle;
-		if (use_ptemod)
-			map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
-#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
-		else if (map->dma_vaddr) {
-			unsigned long bfn;
+		if (map->flags & GNTMAP_device_map)
+			map->unmap_ops[i].dev_bus_addr = map->map_ops[i].dev_bus_addr;
 
-			bfn = pfn_to_bfn(page_to_pfn(map->pages[i]));
-			map->unmap_ops[i].dev_bus_addr = __pfn_to_phys(bfn);
+		if (use_ptemod) {
+			if (map->kmap_ops[i].status == GNTST_okay)
+				map->kunmap_ops[i].handle = map->kmap_ops[i].handle;
+			else if (!err)
+				err = -EINVAL;
 		}
-#endif
 	}
 	return err;
 }
diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 8b59897b2df9..f3024942fbdf 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -386,12 +386,12 @@ static int scsiback_gnttab_data_map_batch(struct gnttab_map_grant_ref *map,
 		return 0;
 
 	err = gnttab_map_refs(map, NULL, pg, cnt);
-	BUG_ON(err);
 	for (i = 0; i < cnt; i++) {
 		if (unlikely(map[i].status != GNTST_okay)) {
 			pr_err("invalid buffer -- could not remap it\n");
 			map[i].handle = SCSIBACK_INVALID_HANDLE;
-			err = -ENOMEM;
+			if (!err)
+				err = -ENOMEM;
 		} else {
 			get_page(pg[i]);
 		}
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index b9c937b3a149..0b1182a3cf41 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -157,6 +157,7 @@ gnttab_set_map_op(struct gnttab_map_grant_ref *map, phys_addr_t addr,
 	map->flags = flags;
 	map->ref = ref;
 	map->dom = domid;
+	map->status = 1; /* arbitrary positive value */
 }
 
 static inline void