From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ffbox0-bg.ffmpeg.org (ffbox0-bg.ffmpeg.org [79.124.17.100]) by master.gitmailbox.com (Postfix) with ESMTPS id 3AFCF45434 for ; Mon, 14 Jul 2025 19:25:33 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.ffmpeg.org (Postfix) with ESMTP id CA30468EE29; Mon, 14 Jul 2025 22:25:29 +0300 (EEST) Received: from btbn.de (btbn.de [144.76.60.213]) by ffbox0-bg.ffmpeg.org (Postfix) with ESMTPS id A244668EDDF for ; Mon, 14 Jul 2025 22:25:23 +0300 (EEST) Received: from [authenticated] by btbn.de (Postfix) with ESMTPSA id B572A2819122E for ; Mon, 14 Jul 2025 21:25:22 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rothenpieler.org; s=mail; t=1752521122; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=c+oKT2jnPInDgKyceILbUkSWHvCu9vAkpa4AbYR7Rvw=; b=U2OXNLBYPLn+ESCHW5TA4qKhQa9dfqm903ijAMAdhxsAUw+8oa6zTbN/fpxakX+w+7Z+SS SU0XW215yBR+I8YD5bQ/qfzGhOqD6zCPOKhGScswTkpRLCaDZ0id7hfp7rIVRnTAx861dC IqsvyyJ+ycT8x3sc9VcVoi+foaSFKGlRSJ5cELC10StWCPjWL+7dJ3z6OEssbyz3/bGmNo d8/GRbWfOA+Izq4hrOFykzzBv0lQ0Fr5m+C51ZaRnXYInYHYpy9f3owpC3EyWEqpcw4Iw4 rU0EvkNOoXelwRjGRHZ8oi0Px/vGnX42KeP+nXGIO1BDIaS3sIWIqxAUYqyfRg== Message-ID: <1c7c687a-945d-464e-88d1-4bb3176f3558@rothenpieler.org> Date: Mon, 14 Jul 2025 21:25:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: ffmpeg-devel@ffmpeg.org References: <20250713011030.1156550-1-michael@niedermayer.cc> <20250714192133.GL29660@pb2> Content-Language: en-US From: Timo Rothenpieler In-Reply-To: <20250714192133.GL29660@pb2> Subject: Re: [FFmpeg-devel] [PATCH 1/5] avformat/flvdec: Check for EOF in AudioPacketTypeMultichannelConfig X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: On 7/14/2025 9:21 PM, Michael Niedermayer wrote: > On Sun, Jul 13, 2025 at 01:42:28PM +0200, Timo Rothenpieler wrote: >> On 7/13/2025 3:10 AM, Michael Niedermayer wrote: >>> Fixes: Infinite loop >>> Fixes: 427538726/clusterfuzz-testcase-minimized-ffmpeg_dem_FLV_fuzzer-6582567304495104 >>> >>> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg >>> Signed-off-by: Michael Niedermayer >>> --- >>> libavformat/flvdec.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c >>> index ac681954cb7..a4fa0157512 100644 >>> --- a/libavformat/flvdec.c >>> +++ b/libavformat/flvdec.c >>> @@ -1715,6 +1715,9 @@ retry_duration: >>> av_log(s, AV_LOG_DEBUG, "Set channel data from MultiChannel info.\n"); >>> + if (avio_feof(s->pb)) >>> + return AVERROR_EOF; >>> + >>> goto next_track; >>> } >>> } else if (stream_type == FLV_STREAM_TYPE_VIDEO) { >> >> I don't think just returning from here is correct. >> The goto next_track right after it already checks for EOF. > >> I do not see how between here and the eof check there there'd be any way to >> infinite loop. > > avio_skip() with a negative value will reset the EOF flag > > >> >> It returns FFERROR_REDO there, which is important to drain queued up >> packages. > > I think the state becomes corrupted once it reads into EOF > that is the size accounting goes "oops" as the code keeps running > things that read and keeps accounting for these reads but in reality > nothing is read as its at EOF > and then it seeks back all these "not reads" and thats where it hits the > infinite loop as theres a mismatch what the code thinks it moved forward > and what it actually moved forward. > Thats how it looked to me at least, i have not verified every step of this > > ill mail you the testcase, then you can check if my analysis is right > and fix the code in a way that can recover queued packets in such truncated > packet at EOF case. > Also please make sure its not forgotten that whatever fix this gets is backported Yeah, I can have a look at it. Probably the size calculation needs fixed then. But as long as the function itself ever returns, which it should by the looks of it, the size calculation becomes irrelevant since an EOF check is the first thing it does. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".