blob: ecfa4305e5bfb2698f56c38f657e2109cb20a9b7 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
|
From: Jan Beulich <jbeulich@suse.com>
Subject: x86/shadow: fix refcount overflow check
Commit c385d27079 ("x86 shadow: for multi-page shadows, explicitly track
the first page") reduced the refcount width to 25, without adjusting the
overflow check. Eliminate the disconnect by using a manifest constant.
Interestingly, up to commit 047782fa01 ("Out-of-sync L1 shadows: OOS
snapshot") the refcount was 27 bits wide, yet the check was already
using 26.
This is XSA-249.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Tim Deegan <tim@xen.org>
---
v2: Simplify expression back to the style it was.
--- a/xen/arch/x86/mm/shadow/private.h
+++ b/xen/arch/x86/mm/shadow/private.h
@@ -529,7 +529,7 @@ static inline int sh_get_ref(struct doma
x = sp->u.sh.count;
nx = x + 1;
- if ( unlikely(nx >= 1U<<26) )
+ if ( unlikely(nx >= (1U << PAGE_SH_REFCOUNT_WIDTH)) )
{
SHADOW_PRINTK("shadow ref overflow, gmfn=%lx smfn=%lx\n",
__backpointer(sp), mfn_x(smfn));
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -82,7 +82,8 @@ struct page_info
unsigned long type:5; /* What kind of shadow is this? */
unsigned long pinned:1; /* Is the shadow pinned? */
unsigned long head:1; /* Is this the first page of the shadow? */
- unsigned long count:25; /* Reference count */
+#define PAGE_SH_REFCOUNT_WIDTH 25
+ unsigned long count:PAGE_SH_REFCOUNT_WIDTH; /* Reference count */
} sh;
/* Page is on a free list: ((count_info & PGC_count_mask) == 0). */
|
