51 lines
2.3 KiB
Diff
51 lines
2.3 KiB
Diff
From daf85701dab05f17e924a48a81edc9195b4a04e8 Mon Sep 17 00:00:00 2001
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From: Ken Sharp <ken.sharp@artifex.com>
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Date: Wed, 21 Dec 2016 16:54:14 +0000
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Subject: [PATCH] fix crash with bad data supplied to makeimagedevice
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Bug #697450 "Null pointer dereference in gx_device_finalize()"
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The problem here is that the code to finalise a device unconditionally
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frees the icc_struct member of the device structure. However this
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particular (weird) device is not setup as a normal device, probably
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because its very, very ancient. Its possible for the initialisation
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of the device to abort with an error before calling gs_make_mem_device()
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which is where the icc_struct member gets allocated (or set to NULL).
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If that happens, then the cleanup code tries to free the device, which
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calls finalize() which tries to free a garbage pointer.
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Setting the device memory to 0x00 after we allocate it means that the
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icc_struct member will be NULL< and our memory manager allows for that
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happily enough, which avoids the problem.
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---
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base/gsdevmem.c | 12 ++++++++++++
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1 file changed, 12 insertions(+)
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diff --git a/base/gsdevmem.c b/base/gsdevmem.c
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index 97b9cf4..fe75bcc 100644
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--- a/base/gsdevmem.c
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+++ b/base/gsdevmem.c
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@@ -225,6 +225,18 @@ gs_makewordimagedevice(gx_device ** pnew_dev, const gs_matrix * pmat,
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if (pnew == 0)
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return_error(gs_error_VMerror);
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+
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+ /* Bug #697450 "Null pointer dereference in gx_device_finalize()"
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+ * If we have incorrect data passed to gs_initialise_wordimagedevice() then the
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+ * initialisation will fail, crucially it will fail *before* it calls
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+ * gs_make_mem_device() which initialises the device. This means that the
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+ * icc_struct member will be uninitialsed, but the device finalise method
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+ * will unconditionally free that memory. Since its a garbage pointer, bad things happen.
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+ * Apparently we do still need makeimagedevice to be available from
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+ * PostScript, so in here just zero the device memory, which means that
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+ * the finalise routine won't have a problem.
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+ */
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+ memset(pnew, 0x00, st_device_memory.ssize);
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code = gs_initialize_wordimagedevice(pnew, pmat, width, height,
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colors, num_colors, word_oriented,
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page_device, mem);
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--
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2.9.3
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