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From f9c6a0549503f00a1ab0ad58a98a30ee99b96770 Mon Sep 17 00:00:00 2001
From: Leon Anavi <leon.anavi@konsulko.com>
Date: Thu, 9 Jul 2026 11:37:04 +0000
Subject: [PATCH] Ppmd7/Ppmd8: Fix SIGABRT in OutputBuffer_Grow
The decode loop could abort in OutputBuffer_Grow() when a resumed
decode thread wrote past the current call's max_length. Stop early
once that limit is reached instead of trying to grow the buffer
further.
Also fix Ppmd8Decoder_decode because it never updated needs_input
when input was fully consumed, unlike Ppmd7.
Fixes test_ppmd7_decode_chunks and the equivalent Ppmd8 case,
which previously aborted deterministically partway through decoding
testdata2.ppmd in small chunks.
This work was sponsored by GOVCERT.LU.
Upstream-Status: Pending [https://github.com/miurahr/pyppmd/pull/131/]
Signed-off-by: Leon Anavi <leon.anavi@konsulko.com>
---
src/ext/_ppmdmodule.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/src/ext/_ppmdmodule.c b/src/ext/_ppmdmodule.c
index dafa1c5..94f7f18 100644
--- a/src/ext/_ppmdmodule.c
+++ b/src/ext/_ppmdmodule.c
@@ -531,6 +531,12 @@ Ppmd7Decoder_decode(Ppmd7Decoder *self, PyObject *args, PyObject *kwargs) {
break;
}
if (out->pos == out->size) {
+ /* Already reached max_length for this call; stop instead of
+ growing (avoids rest<=0 assert in OutputBuffer_Grow) */
+ if (self->blocksOutputBuffer->max_length >= 0 &&
+ self->blocksOutputBuffer->allocated >= self->blocksOutputBuffer->max_length) {
+ break;
+ }
if (OutputBuffer_Grow(self->blocksOutputBuffer, out) < 0) {
PyErr_SetString(PyExc_ValueError, "No Memory.");
goto error;
@@ -1276,6 +1282,11 @@ Ppmd8Decoder_decode(Ppmd8Decoder *self, PyObject *args, PyObject *kwargs) {
break; // filled expected
}
if (out->pos == out->size) {
+ /* Same guard as for Ppmd7Decoder_decode() above */
+ if (self->blocksOutputBuffer->max_length >= 0 &&
+ self->blocksOutputBuffer->allocated >= self->blocksOutputBuffer->max_length) {
+ break;
+ }
if (OutputBuffer_Grow(self->blocksOutputBuffer, out) < 0) {
PyErr_SetString(PyExc_ValueError, "L1586: Unknown status");
goto error;
@@ -1303,6 +1314,11 @@ Ppmd8Decoder_decode(Ppmd8Decoder *self, PyObject *args, PyObject *kwargs) {
self->in_begin = 0;
self->in_end = 0;
}
+ if (self->eof) {
+ self->needs_input = False;
+ } else {
+ self->needs_input = True;
+ }
} else {
const size_t data_size = in->size - in->pos;
self->needs_input = False;
--
2.47.3
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