package/ghostscript: fix CVE-2021-45949

Ghostscript GhostPDL 9.50 through 9.54.0 has a heap-based buffer
overflow in sampled_data_finish (called from sampled_data_continue and
interp).

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/ghostscript/0004-Bug-703902-Fix-op-stack-management-in-sampled_data_continue.patch

@@ -0,0 +1,68 @@
+From 2a3129365d3bc0d4a41f107ef175920d1505d1f7 Mon Sep 17 00:00:00 2001
+From: Chris Liddell <chris.liddell@artifex.com>
+Date: Tue, 1 Jun 2021 19:57:16 +0100
+Subject: [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
+
+[Retrieved from:
+https://git.ghostscript.com/?p=ghostpdl.git;a=commit;h=2a3129365d3bc0d4a41f107ef175920d1505d1f7]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ psi/zfsample.c | 16 ++++++++++------
+ 1 file changed, 10 insertions(+), 6 deletions(-)
+
+diff --git a/psi/zfsample.c b/psi/zfsample.c
+index 0e8e4bc8d..00cd0cfdd 100644
+--- a/psi/zfsample.c
++++ b/psi/zfsample.c
+@@ -533,15 +533,19 @@ sampled_data_continue(i_ctx_t *i_ctx_p)
+         for (j = 0; j < bps; j++)
+             data_ptr[bps * i + j] = (byte)(cv >> ((bps - 1 - j) * 8));	/* MSB first */
+     }
+-    pop(num_out);		    /* Move op to base of result values */
+ 
+-    /* Check if we are done collecting data. */
++    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 +558,11 @@ 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);
+             }
+-- 
+2.25.1
+

package/ghostscript/ghostscript.mk

@@ -27,6 +27,9 @@ GHOSTSCRIPT_IGNORE_CVES += CVE-2021-3781
 # 0003-oss-fuzz-30715-Check-stack-limits-after-function-evaluation.patch
 GHOSTSCRIPT_IGNORE_CVES += CVE-2021-45944
 
+# 0004-Bug-703902-Fix-op-stack-management-in-sampled_data_continue.patch
+GHOSTSCRIPT_IGNORE_CVES += CVE-2021-45949
+
 # Ghostscript includes (old) copies of several libraries, delete them.
 # Inspired by linuxfromscratch:
 # http://www.linuxfromscratch.org/blfs/view/svn/pst/gs.html