From de0a032d8ebd05999a702f304b7eb58ea189f14a Mon Sep 17 00:00:00 2001
From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Tue, 6 Nov 2018 14:40:41 +0100
Subject: xcursor: Fix heap overflows when parsing malicious files
It is possible to trigger heap overflows due to an integer overflow
while parsing images.
The integer overflow occurs because the chosen limit 0x10000 for
dimensions is too large for 32 bit systems, because each pixel takes
4 bytes. Properly chosen values allow an overflow which in turn will
lead to less allocated memory than needed for subsequent reads.
See also:
https://cgit.freedesktop.org/xorg/lib/libXcursor/commit/?id=4794b5dd34688158fb51a2943032569d3780c4b8
https://gitlab.freedesktop.org/wayland/wayland/commit/5d201df72f3d4f4cb8b8f75f980169b03507da38
---
xcursor/xcursor.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/xcursor/xcursor.c b/xcursor/xcursor.c
index 32711105..6690da1a 100644
--- a/xcursor/xcursor.c
+++ b/xcursor/xcursor.c
@@ -203,6 +203,11 @@ XcursorImageCreate (int width, int height)
{
XcursorImage *image;
+ if (width < 0 || height < 0)
+ return NULL;
+ if (width > XCURSOR_IMAGE_MAX_SIZE || height > XCURSOR_IMAGE_MAX_SIZE)
+ return NULL;
+
image = malloc (sizeof (XcursorImage) +
width * height * sizeof (XcursorPixel));
if (!image)
@@ -483,7 +488,8 @@ _XcursorReadImage (XcursorFile *file,
if (!_XcursorReadUInt (file, &head.delay))
return NULL;
/* sanity check data */
- if (head.width >= 0x10000 || head.height > 0x10000)
+ if (head.width > XCURSOR_IMAGE_MAX_SIZE ||
+ head.height > XCURSOR_IMAGE_MAX_SIZE)
return NULL;
if (head.width == 0 || head.height == 0)
return NULL;
@@ -877,9 +883,11 @@ load_all_cursors_from_dir(const char *path, int size,
return;
for(ent = readdir(dir); ent; ent = readdir(dir)) {
+#ifdef _DIRENT_HAVE_D_TYPE
if (ent->d_type != DT_UNKNOWN &&
(ent->d_type != DT_REG && ent->d_type != DT_LNK))
continue;
+#endif
full = _XcursorBuildFullname(path, "", ent->d_name);
if (!full)
--
cgit v1.2.3