[patch] ghostscript-gpl-CVE-2016-10220.patch

ghostscript-gpl-CVE-2016-10220.patch (text/plain), 2.38 KB, created by Andrey Ovcharov on 2017-06-07 13:29:16 UTC

From daf85701dab05f17e924a48a81edc9195b4a04e8 Mon Sep 17 00:00:00 2001
From: Ken Sharp <[e-mail]>
Date: Wed, 21 Dec 2016 16:54:14 +0000
Subject: [PATCH] fix crash with bad data supplied to makeimagedevice

Bug #697450 "Null pointer dereference in gx_device_finalize()"

The problem here is that the code to finalise a device unconditionally
frees the icc_struct member of the device structure. However this
particular (weird) device is not setup as a normal device, probably
because its very, very ancient. Its possible for the initialisation
of the device to abort with an error before calling gs_make_mem_device()
which is where the icc_struct member gets allocated (or set to NULL).

If that happens, then the cleanup code tries to free the device, which
calls finalize() which tries to free a garbage pointer.

Setting the device memory to 0x00 after we allocate it means that the
icc_struct member will be NULL< and our memory manager allows for that
happily enough, which avoids the problem.

Upstream-Status: Backport
CVE: CVE-2016-10220

Signed-off-by: Catalin Enache <[e-mail]>
---
 base/gsdevmem.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/base/gsdevmem.c b/base/gsdevmem.c
index 97b9cf4..fe75bcc 100644
--- a/base/gsdevmem.c
+++ b/base/gsdevmem.c
@@ -225,6 +225,18 @@ gs_makewordimagedevice(gx_device ** pnew_dev, const gs_matrix * pmat,
 
     if (pnew == 0)
         return_error(gs_error_VMerror);
+
+    /* Bug #697450 "Null pointer dereference in gx_device_finalize()"
+     * If we have incorrect data passed to gs_initialise_wordimagedevice() then the
+     * initialisation will fail, crucially it will fail *before* it calls
+     * gs_make_mem_device() which initialises the device. This means that the
+     * icc_struct member will be uninitialsed, but the device finalise method
+     * will unconditionally free that memory. Since its a garbage pointer, bad things happen.
+     * Apparently we do still need makeimagedevice to be available from
+     * PostScript, so in here just zero the device memory, which means that
+     * the finalise routine won't have a problem.
+     */
+    memset(pnew, 0x00, st_device_memory.ssize);
     code = gs_initialize_wordimagedevice(pnew, pmat, width, height,
                                          colors, num_colors, word_oriented,
                                          page_device, mem);
-- 
2.10.2