libxcursor: CVE-2017-16612

affects: <= 1.1.14

CVE-2017-16612: Fix heap overflows when parsing malicious files

It is possible to trigger heap overflows due to an integer overflow
while parsing images and a signedness issue while parsing comments.

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.

The signedness bug is triggered by reading the length of a comment
as unsigned int, but casting it to int when calling the function
XcursorCommentCreate. Turning length into a negative value allows the
check against XCURSOR_COMMENT_MAX_LEN to pass, and the following
addition of sizeof (XcursorComment) + 1 makes it possible to allocate
less memory than needed for subsequent reads.

Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.com>
Signed-off-by: Armin Kuster <akuster@mvista.com>

2 files changed, 77 insertions, 0 deletions

diff --git a/meta/recipes-graphics/xorg-lib/libxcursor/CVE-2017-16612.patch b/meta/recipes-graphics/xorg-lib/libxcursor/CVE-2017-16612.patch
new file mode 100644
index 0000000000..9a1b12e4f4
--- /dev/null
+++ b/meta/recipes-graphics/xorg-lib/libxcursor/CVE-2017-16612.patch
@@ -0,0 +1,75 @@
+From 4794b5dd34688158fb51a2943032569d3780c4b8 Mon Sep 17 00:00:00 2001
+From: Tobias Stoeckmann <tobias@stoeckmann.org>
+Date: Sat, 21 Oct 2017 23:47:52 +0200
+Subject: Fix heap overflows when parsing malicious files. (CVE-2017-16612)
+
+It is possible to trigger heap overflows due to an integer overflow
+while parsing images and a signedness issue while parsing comments.
+
+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.
+
+The signedness bug is triggered by reading the length of a comment
+as unsigned int, but casting it to int when calling the function
+XcursorCommentCreate. Turning length into a negative value allows the
+check against XCURSOR_COMMENT_MAX_LEN to pass, and the following
+addition of sizeof (XcursorComment) + 1 makes it possible to allocate
+less memory than needed for subsequent reads.
+
+Upstream-Status: Backport from v1.1.15
+CVE: CVE-2017-16612
+
+Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.com>
+---
+ src/file.c | 12 ++++++++++--
+ 1 file changed, 10 insertions(+), 2 deletions(-)
+
+diff --git a/src/file.c b/src/file.c
+index 43163c2..da16277 100644
+--- a/src/file.c
++++ b/src/file.c
+@@ -29,6 +29,11 @@ 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)
+@@ -101,7 +106,7 @@ XcursorCommentCreate (XcursorUInt comment_type, int length)
+ {
+     XcursorComment  *comment;
+ 
+-    if (length > XCURSOR_COMMENT_MAX_LEN)
++    if (length < 0 || length > XCURSOR_COMMENT_MAX_LEN)
+ 	return NULL;
+ 
+     comment = malloc (sizeof (XcursorComment) + length + 1);
+@@ -448,7 +453,8 @@ _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;
+@@ -457,6 +463,8 @@ _XcursorReadImage (XcursorFile		*file,
+ 
+     /* Create the image and initialize it */
+     image = XcursorImageCreate (head.width, head.height);
++    if (image == NULL)
++	return NULL;
+     if (chunkHeader.version < image->version)
+ 	image->version = chunkHeader.version;
+     image->size = chunkHeader.subtype;
+-- 
+cgit v1.1
+
diff --git a/meta/recipes-graphics/xorg-lib/libxcursor_1.1.14.bb b/meta/recipes-graphics/xorg-lib/libxcursor_1.1.14.bb
index 17629047b7..ccc4347820 100644
--- a/meta/recipes-graphics/xorg-lib/libxcursor_1.1.14.bb
+++ b/meta/recipes-graphics/xorg-lib/libxcursor_1.1.14.bb
@@ -16,6 +16,8 @@ BBCLASSEXTEND = "native nativesdk"
 
 PE = "1"
 
+SRC_URI += "file://CVE-2017-16612.patch"
+
 XORG_PN = "libXcursor"
 
 SRC_URI[md5sum] = "1e7c17afbbce83e2215917047c57d1b3"