--- /dev/null
+From 6643ff0cb837db3eade489ffff21e3e92eee2ae0 Mon Sep 17 00:00:00 2001
+From: Chris Liddell <chris.liddell@artifex.com>
+Date: Fri, 28 Jan 2022 08:21:19 +0000
+Subject: [PATCH] [PATCH] Bug 703902: Fix op stack management in
+ sampled_data_continue()
+
+Replace pop() (which does no checking, and doesn't handle stack extension
+blocks) with ref_stack_pop() which does do all that.
+
+We still use pop() in one case (it's faster), but we have to later use
+ref_stack_pop() before calling sampled_data_sample() which also accesses the
+op stack.
+
+Fixes:
+https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=34675
+
+Upstream-Status: Backported [https://git.ghostscript.com/?p=ghostpdl.git;a=commit;h=2a3129365d3bc0d4a41f107ef175920d1505d1f7]
+CVE: CVE-2021-45949
+Signed-off-by: Minjae Kim <flowergom@gmail.com>
+---
+ psi/zfsample.c | 13 ++++++++-----
+ 1 file changed, 8 insertions(+), 5 deletions(-)
+
+diff --git a/psi/zfsample.c b/psi/zfsample.c
+index 0023fa4..f84671f 100644
+--- a/psi/zfsample.c
++++ b/psi/zfsample.c
+@@ -534,14 +534,17 @@ sampled_data_continue(i_ctx_t *i_ctx_p)
+ data_ptr[bps * i + j] = (byte)(cv >> ((bps - 1 - j) * 8)); /* MSB first */
+ }
+ pop(num_out); /* Move op to base of result values */
+-
++ /* From here on, we have to use ref_stack_pop() rather than pop()
++ so that it handles stack extension blocks properly, before calling
++ sampled_data_sample() which also uses the op stack.
++ */
+ /* Check if we are done collecting data. */
+
+ if (increment_cube_indexes(params, penum->indexes)) {
+ if (stack_depth_adjust == 0)
+- pop(O_STACK_PAD); /* Remove spare stack space */
++ ref_stack_pop(&o_stack, O_STACK_PAD); /* Remove spare stack space */
+ else
+- pop(stack_depth_adjust - num_out);
++ ref_stack_pop(&o_stack, stack_depth_adjust - num_out);
+ /* Execute the closing procedure, if given */
+ code = 0;
+ if (esp_finish_proc != 0)
+@@ -554,11 +557,11 @@ sampled_data_continue(i_ctx_t *i_ctx_p)
+ if ((O_STACK_PAD - stack_depth_adjust) < 0) {
+ stack_depth_adjust = -(O_STACK_PAD - stack_depth_adjust);
+ check_op(stack_depth_adjust);
+- pop(stack_depth_adjust);
++ ref_stack_pop(&o_stack, stack_depth_adjust);
+ }
+ else {
+ check_ostack(O_STACK_PAD - stack_depth_adjust);
+- push(O_STACK_PAD - stack_depth_adjust);
++ ref_stack_push(&o_stack, O_STACK_PAD - stack_depth_adjust);
+ for (i=0;i<O_STACK_PAD - stack_depth_adjust;i++)
+ make_null(op - i);
+ }
+--
+2.17.1
+
--- /dev/null
+From 7861fcad13c497728189feafb41cd57b5b50ea25 Mon Sep 17 00:00:00 2001
+From: Chris Liddell <chris.liddell@artifex.com>
+Date: Fri, 12 Feb 2021 10:34:23 +0000
+Subject: [PATCH] oss-fuzz 30715: Check stack limits after function evaluation.
+
+During function result sampling, after the callout to the Postscript
+interpreter, make sure there is enough stack space available before pushing
+or popping entries.
+
+In thise case, the Postscript procedure for the "function" is totally invalid
+(as a function), and leaves the op stack in an unrecoverable state (as far as
+function evaluation is concerned). We end up popping more entries off the
+stack than are available.
+
+To cope, add in stack limit checking to throw an appropriate error when this
+happens.
+
+Upstream-Status: Backported [https://git.ghostscript.com/?p=ghostpdl.git;a=patch;h=7861fcad13c497728189feafb41cd57b5b50ea25]
+Signed-off-by: Minjae Kim <flowergom@gmail.com>
+---
+ psi/zfsample.c | 14 +++++++++++---
+ 1 file changed, 11 insertions(+), 3 deletions(-)
+
+diff --git a/psi/zfsample.c b/psi/zfsample.c
+index 290809405..652ae02c6 100644
+--- a/psi/zfsample.c
++++ b/psi/zfsample.c
+@@ -551,9 +551,17 @@ sampled_data_continue(i_ctx_t *i_ctx_p)
+ } else {
+ if (stack_depth_adjust) {
+ stack_depth_adjust -= num_out;
+- push(O_STACK_PAD - stack_depth_adjust);
+- for (i=0;i<O_STACK_PAD - stack_depth_adjust;i++)
+- make_null(op - i);
++ if ((O_STACK_PAD - stack_depth_adjust) < 0) {
++ stack_depth_adjust = -(O_STACK_PAD - stack_depth_adjust);
++ check_op(stack_depth_adjust);
++ pop(stack_depth_adjust);
++ }
++ else {
++ check_ostack(O_STACK_PAD - stack_depth_adjust);
++ push(O_STACK_PAD - stack_depth_adjust);
++ for (i=0;i<O_STACK_PAD - stack_depth_adjust;i++)
++ make_null(op - i);
++ }
+ }
+ }
+
+--
+2.25.1
+
