From 7da437c2f5440a9230e482d58d86b579221b3207 Mon Sep 17 00:00:00 2001
From: Mauro Matteo Cascella <mcascell@redhat.com>
Date: Thu, 7 Apr 2022 10:17:12 +0200
Subject: [PATCH 2/2] ui/cursor: fix integer overflow in cursor_alloc
 (CVE-2021-4206)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Prevent potential integer overflow by limiting 'width' and 'height' to
512x512. Also change 'datasize' type to size_t. Refer to security
advisory https://starlabs.sg/advisories/22-4206/ for more information.

Fixes: CVE-2021-4206
Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20220407081712.345609-1-mcascell@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 hw/display/qxl-render.c | 7 +++++++
 hw/display/vmware_vga.c | 2 ++
 ui/cursor.c             | 8 +++++++-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/hw/display/qxl-render.c b/hw/display/qxl-render.c
index 237ed293ba..ca217004bf 100644
--- a/hw/display/qxl-render.c
+++ b/hw/display/qxl-render.c
@@ -247,6 +247,13 @@ static QEMUCursor *qxl_cursor(PCIQXLDevice *qxl, QXLCursor *cursor,
     size_t size;
 
     c = cursor_alloc(cursor->header.width, cursor->header.height);
+
+    if (!c) {
+        qxl_set_guest_bug(qxl, "%s: cursor %ux%u alloc error", __func__,
+                cursor->header.width, cursor->header.height);
+        goto fail;
+    }
+
     c->hot_x = cursor->header.hot_spot_x;
     c->hot_y = cursor->header.hot_spot_y;
     switch (cursor->header.type) {
diff --git a/hw/display/vmware_vga.c b/hw/display/vmware_vga.c
index e2969a6c81..2b81d6122f 100644
--- a/hw/display/vmware_vga.c
+++ b/hw/display/vmware_vga.c
@@ -509,6 +509,8 @@ static inline void vmsvga_cursor_define(struct vmsvga_state_s *s,
     int i, pixels;
 
     qc = cursor_alloc(c->width, c->height);
+    assert(qc != NULL);
+
     qc->hot_x = c->hot_x;
     qc->hot_y = c->hot_y;
     switch (c->bpp) {
diff --git a/ui/cursor.c b/ui/cursor.c
index 1d62ddd4d0..835f0802f9 100644
--- a/ui/cursor.c
+++ b/ui/cursor.c
@@ -46,6 +46,8 @@ static QEMUCursor *cursor_parse_xpm(const char *xpm[])
 
     /* parse pixel data */
     c = cursor_alloc(width, height);
+    assert(c != NULL);
+
     for (pixel = 0, y = 0; y < height; y++, line++) {
         for (x = 0; x < height; x++, pixel++) {
             idx = xpm[line][x];
@@ -91,7 +93,11 @@ QEMUCursor *cursor_builtin_left_ptr(void)
 QEMUCursor *cursor_alloc(int width, int height)
 {
     QEMUCursor *c;
-    int datasize = width * height * sizeof(uint32_t);
+    size_t datasize = width * height * sizeof(uint32_t);
+
+    if (width > 512 || height > 512) {
+        return NULL;
+    }
 
     c = g_malloc0(sizeof(QEMUCursor) + datasize);
     c->width  = width;
-- 
2.27.0