[FFmpeg-devel] [PR] avcodec/cngdec: Fix SIGILL issue in cng_decode_frame() (PR #22300)

[yuyong05 via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #22300 opened by yuyong05
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22300
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/22300.patch

The issue is caused by floating-point to integer overflow conversion
at function av_clip_int16(p->filter_out[i + p->order]).
The float value is -2,441,986,048.0 out of bound, less than
INT_MIN(-2,147,483,648), which leads to UB and SIGILL crash.

- Handle NAN using isfinite()
- Clip float value into valid range of int16 with av_clipf


>From 93a0975bac8d0dc371da04195210c7cd6070646b Mon Sep 17 00:00:00 2001
From: Yong Yu <yuyong05@gmail.com>
Date: Thu, 26 Feb 2026 13:35:10 -0800
Subject: [PATCH] avcodec/cngdec: Fix SIGILL issue in cng_decode_frame()

The issue is caused by floating-point to integer overflow conversion
at function av_clip_int16(p->filter_out[i + p->order]).
The float value is -2,441,986,048.0 out of bound, less than
INT_MIN(-2,147,483,648), which leads to UB and SIGILL crash.

- Handle NAN using isfinite()
- Clip float value into valid range of int16 with av_clipf
---
 libavcodec/cngdec.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/libavcodec/cngdec.c b/libavcodec/cngdec.c
index eb37c33eb4..b46f5fef95 100644
--- a/libavcodec/cngdec.c
+++ b/libavcodec/cngdec.c
@@ -153,8 +153,10 @@ static int cng_decode_frame(AVCodecContext *avctx, AVFrame *frame,
     if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
         return ret;
     buf_out = (int16_t *)frame->data[0];
-    for (i = 0; i < avctx->frame_size; i++)
-        buf_out[i] = av_clip_int16(p->filter_out[i + p->order]);
+    for (i = 0; i < avctx->frame_size; i++) {
+        const float f = p->filter_out[i + p->order];
+        buf_out[i] = !isfinite(f) ? 0 : lrintf(av_clipf(f, INT16_MIN, INT16_MAX));
+    }
     memcpy(p->filter_out, p->filter_out + avctx->frame_size,
            p->order * sizeof(*p->filter_out));
 
-- 
2.52.0

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