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
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
|
From 99c644fc8488657bdd106717df7446d606f9ef22 Mon Sep 17 00:00:00 2001
From: Alan Coopersmith <alan.coopersmith@oracle.com>
Date: Fri, 8 Mar 2013 19:55:55 -0800
Subject: [PATCH 2/2] integer overflow in XineramaQueryScreens()
[CVE-2013-1985]
If the reported number of screens is too large, the calculations to
allocate memory for them may overflow, leaving us writing beyond the
bounds of the allocation.
Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
---
src/Xinerama.c | 44 ++++++++++++++++++++++++++++----------------
1 file changed, 28 insertions(+), 16 deletions(-)
diff --git a/src/Xinerama.c b/src/Xinerama.c
index 04189b6..67a35b5 100644
--- a/src/Xinerama.c
+++ b/src/Xinerama.c
@@ -303,24 +303,36 @@ XineramaQueryScreens(
return NULL;
}
- if(rep.number) {
- if((scrnInfo = Xmalloc(sizeof(XineramaScreenInfo) * rep.number))) {
+ /*
+ * rep.number is a CARD32 so could be as large as 2^32
+ * The X11 protocol limits the total screen size to 64k x 64k,
+ * and no screen can be smaller than a pixel. While technically
+ * that means we could theoretically reach 2^32 screens, and that's
+ * not even taking overlap into account, Xorg is currently limited
+ * to 16 screens, and few known servers have a much higher limit,
+ * so 1024 seems more than enough to prevent both integer overflow
+ * and insane X server responses causing massive memory allocation.
+ */
+ if ((rep.number > 0) && (rep.number <= 1024))
+ scrnInfo = Xmalloc(sizeof(XineramaScreenInfo) * rep.number);
+ if (scrnInfo != NULL) {
+ int i;
+
+ for (i = 0; i < rep.number; i++) {
xXineramaScreenInfo scratch;
- int i;
-
- for(i = 0; i < rep.number; i++) {
- _XRead(dpy, (char*)(&scratch), sz_XineramaScreenInfo);
- scrnInfo[i].screen_number = i;
- scrnInfo[i].x_org = scratch.x_org;
- scrnInfo[i].y_org = scratch.y_org;
- scrnInfo[i].width = scratch.width;
- scrnInfo[i].height = scratch.height;
- }
-
- *number = rep.number;
- } else
- _XEatDataWords(dpy, rep.length);
+
+ _XRead(dpy, (char*)(&scratch), sz_XineramaScreenInfo);
+
+ scrnInfo[i].screen_number = i;
+ scrnInfo[i].x_org = scratch.x_org;
+ scrnInfo[i].y_org = scratch.y_org;
+ scrnInfo[i].width = scratch.width;
+ scrnInfo[i].height = scratch.height;
+ }
+
+ *number = rep.number;
} else {
+ _XEatDataWords(dpy, rep.length);
*number = 0;
}
--
1.8.2.3
|
