| 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 |
| |