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From daf85701dab05f17e924a48a81edc9195b4a04e8 Mon Sep 17 00:00:00 2001
From: Ken Sharp <ken.sharp@artifex.com>
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 <catalin.enache@windriver.com>
---
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
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