xen/arm: don't ignore return errors from set_phys_to_machine

stable inclusion
from linux-4.19.177
commit 271a3984f73c485f4c1b796a61cc5bd3994a0463
CVE: CVE-2021-26932

--------------------------------

commit 36bf1dfb upstream.

set_phys_to_machine can fail due to lack of memory, see the kzalloc call
in arch/arm/xen/p2m.c:__set_phys_to_machine_multi.

Don't ignore the potential return error in set_foreign_p2m_mapping,
returning it to the caller instead.

This is part of XSA-361.
Signed-off-by: NStefano Stabellini <stefano.stabellini@xilinx.com>
Cc: stable@vger.kernel.org
Reviewed-by: NJulien Grall <jgrall@amazon.com>
Signed-off-by: NJuergen Gross <jgross@suse.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>

arch/arm/xen/p2m.c

@@ -93,8 +93,10 @@ 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;