linux-kernel - [PATCH 5.4 30/33] xen/pvcalls: use alloc/free_pages

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Date:   Thu, 10 Mar 2022 15:19:31 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Simon Gaiser <simon@...isiblethingslab.com>,
        Juergen Gross <jgross@...e.com>,
        Jan Beulich <jbeulich@...e.com>
Subject: [PATCH 5.4 30/33] xen/pvcalls: use alloc/free_pages_exact()

From: Juergen Gross <jgross@...e.com>

Commit b0576cc9c6b843d99c6982888d59a56209341888 upstream.

Instead of __get_free_pages() and free_pages() use alloc_pages_exact()
and free_pages_exact(). This is in preparation of a change of
gnttab_end_foreign_access() which will prohibit use of high-order
pages.

This is part of CVE-2022-23041 / XSA-396.

Reported-by: Simon Gaiser <simon@...isiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@...e.com>
Reviewed-by: Jan Beulich <jbeulich@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/xen/pvcalls-front.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -337,8 +337,8 @@ static void free_active_ring(struct sock
 	if (!map->active.ring)
 		return;
 
-	free_pages((unsigned long)map->active.data.in,
-			map->active.ring->ring_order);
+	free_pages_exact(map->active.data.in,
+			 PAGE_SIZE << map->active.ring->ring_order);
 	free_page((unsigned long)map->active.ring);
 }
 
@@ -352,8 +352,8 @@ static int alloc_active_ring(struct sock
 		goto out;
 
 	map->active.ring->ring_order = PVCALLS_RING_ORDER;
-	bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
-					PVCALLS_RING_ORDER);
+	bytes = alloc_pages_exact(PAGE_SIZE << PVCALLS_RING_ORDER,
+				  GFP_KERNEL | __GFP_ZERO);
 	if (!bytes)
 		goto out;