xen/blkfront: fix leaking data in shared pages

When allocating pages to be used for shared communication with the
backend always zero them, this avoids leaking unintended data present
on the pages.

This is CVE-2022-26365, part of XSA-403.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 33f04ef78984c77ed32b576d38729b2d65aa7126..4b3bef6ace68fde4dfdb286363c3bbae7868957f 100644 (file)
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -311,7 +311,7 @@ static int fill_grant_buffer(struct blkfront_ring_info *rinfo, int num)
                        goto out_of_memory;
 
                if (info->feature_persistent) {
-                       granted_page = alloc_page(GFP_NOIO);
+                       granted_page = alloc_page(GFP_NOIO | __GFP_ZERO);
                        if (!granted_page) {
                                kfree(gnt_list_entry);
                                goto out_of_memory;
@@ -2183,7 +2183,8 @@ static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo)
 
                BUG_ON(!list_empty(&rinfo->indirect_pages));
                for (i = 0; i < num; i++) {
-                       struct page *indirect_page = alloc_page(GFP_KERNEL);
+                       struct page *indirect_page = alloc_page(GFP_KERNEL |
+                                                               __GFP_ZERO);
                        if (!indirect_page)
                                goto out_of_memory;
                        list_add(&indirect_page->lru, &rinfo->indirect_pages);