[PATCH 5.15 78/98] xen/blkfront: fix leaking data in shared pages

Greg Kroah-Hartman
2022-07-05T12:30:58Z

From: Roger Pau Monne <roger.pau@citrix.com>

commit 2f446ffe9d737e9a844b97887919c4fda18246e7 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/block/xen-blkfront.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -312,7 +312,7 @@ static int fill_grant_buffer(struct blkf
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;
@@ -1692,7 +1692,7 @@ static int setup_blkring(struct xenbus_d
for (i = 0; i < info->nr_ring_pages; i++)
rinfo->ring_ref[i] = GRANT_INVALID_REF;

- sring = alloc_pages_exact(ring_size, GFP_NOIO);
+ sring = alloc_pages_exact(ring_size, GFP_NOIO | __GFP_ZERO);
if (!sring) {
xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
return -ENOMEM;
@@ -2209,7 +2209,8 @@ static int blkfront_setup_indirect(struc

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);