[FFmpeg-devel] [PATCH] Update libavformat/segafilmenc.c (PR #20922)

[Shubin123 via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20922 opened by Shubin123
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20922
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20922.patch

The film_write_packet() function reads encoded_buf_size from packet
data via AV_RB24() and uses it in a modulo operation without validation.
When the data contains zeros at this position, it causes division by zero.

Add validation to return AVERROR_INVALIDDATA when encoded_buf_size is zero.


>From 27c5051a7a659f8723bb5fc6afe754988a9c2c4e Mon Sep 17 00:00:00 2001
From: Shubin123 <wangshubin130@gmail.com>
Date: Fri, 14 Nov 2025 21:09:50 +0000
Subject: [PATCH] Update libavformat/segafilmenc.c

The film_write_packet() function reads encoded_buf_size from packet
data via AV_RB24() and uses it in a modulo operation without validation.
When the data contains zeros at this position, it causes division by zero.

Add validation to return AVERROR_INVALIDDATA when encoded_buf_size is zero.
---
 libavformat/segafilmenc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libavformat/segafilmenc.c b/libavformat/segafilmenc.c
index 88a5b9f972..2206ff9033 100644
--- a/libavformat/segafilmenc.c
+++ b/libavformat/segafilmenc.c
@@ -58,6 +58,10 @@ static int film_write_packet(AVFormatContext *format_context, AVPacket *pkt)
     if (codec_id == AV_CODEC_ID_CINEPAK) {
         encoded_buf_size = AV_RB24(&pkt->data[1]);
         /* Already Sega Cinepak, so no need to reformat the packets */
+        if (encoded_buf_size == 0) {
+            av_log(format_context, AV_LOG_ERROR, "Invalid encoded_buf_size 0\n");
+            return AVERROR_INVALIDDATA;
+        }
         if (encoded_buf_size != pkt->size && (pkt->size % encoded_buf_size) != 0) {
             avio_write(pb, pkt->data, pkt->size);
         } else {
-- 
2.49.1

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