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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
Upstream-Status: Backported [https://git.ghostscript.com/?p=ghostpdl.git;a=commit;h=2a3129365d3bc0d4a41f107ef175920d1505d1f7]
CVE: CVE-2021-45949
Signed-off-by: Lee Chee Yang <chee.yang.lee@intel.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
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