[PATCH 4.9 21/29] xen/netfront: fix leaking data in shared pages

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

commit 307c8de2b02344805ebead3440d8feed28f2f010 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-2022-33740, 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/net/xen-netfront.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -260,7 +260,7 @@ static struct sk_buff *xennet_alloc_one_
 	if (unlikely(!skb))
 		return NULL;
 
-	page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
+	page = alloc_page(GFP_ATOMIC | __GFP_NOWARN | __GFP_ZERO);
 	if (!page) {
 		kfree_skb(skb);
 		return NULL;