From daf85701dab05f17e924a48a81edc9195b4a04e8 Mon Sep 17 00:00:00 2001 From: Ken Sharp 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 --- 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