[FFmpeg-devel] [PR] avformat/img2dec: reject input images too big to fit into a single packet (PR #21337)

[Timo Rothenpieler via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #21337 opened by Timo Rothenpieler (BtbN)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21337
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21337.patch

(cherry picked from commit f6a95c7eb786f895812adaaa08d2fe91c4d4caf8)


>From 7ce72077704d5351d2c4a8d06016548e0f8a730c Mon Sep 17 00:00:00 2001
From: Timo Rothenpieler <timo@rothenpieler.org>
Date: Wed, 31 Dec 2025 03:41:21 +0100
Subject: [PATCH] avformat/img2dec: reject input images too big to fit into a
 single packet

Not entirely sure if it should instead use some entirely different
approach here, given that images exceeding 2GB don't seem that crazy
to me, but so far processing such images results in a heap overflow,
since the size addition overflows and a much too small packet is
allocated and its size never checked again when writing into it.

Fixes #YWH-PGM40646-32

(cherry picked from commit f6a95c7eb786f895812adaaa08d2fe91c4d4caf8)
---
 libavformat/img2dec.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/libavformat/img2dec.c b/libavformat/img2dec.c
index 3389fa818e..2bcbfafdfc 100644
--- a/libavformat/img2dec.c
+++ b/libavformat/img2dec.c
@@ -416,8 +416,10 @@ int ff_img_read_packet(AVFormatContext *s1, AVPacket *pkt)
     char filename_bytes[1024];
     char *filename = filename_bytes;
     int i, res;
-    int size[3]           = { 0 }, ret[3] = { 0 };
-    AVIOContext *f[3]     = { NULL };
+    int ret[3] = { 0 };
+    int64_t size[3] = { 0 };
+    int64_t total_size;
+    AVIOContext *f[3] = { NULL };
     AVCodecParameters *par = s1->streams[0]->codecpar;
 
     if (!s->is_pipe) {
@@ -497,7 +499,17 @@ int ff_img_read_packet(AVFormatContext *s1, AVPacket *pkt)
         }
     }
 
-    res = av_new_packet(pkt, size[0] + size[1] + size[2]);
+    total_size = size[0];
+    if (total_size > INT64_MAX - size[1])
+        return AVERROR_INVALIDDATA;
+    total_size += size[1];
+    if (total_size > INT64_MAX - size[2])
+        return AVERROR_INVALIDDATA;
+    total_size += size[2];
+    if (total_size > INT_MAX)
+        return AVERROR_INVALIDDATA;
+
+    res = av_new_packet(pkt, total_size);
     if (res < 0) {
         goto fail;
     }
-- 
2.49.1

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