Re: [FFmpeg-devel] [PATCH v2 1/3] fftools/ffmpeg_filter: fix NULL pointer dereference

From: Anton Khirnov <anton@khirnov.net>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Cc: Zhao Zhili <zhilizhao@tencent.com>
Subject: Re: [FFmpeg-devel] [PATCH v2 1/3] fftools/ffmpeg_filter: fix NULL pointer dereference
Date: Tue, 19 Dec 2023 11:32:17 +0100
Message-ID: <170298193747.8914.3330104981111843352@lain.khirnov.net> (raw)
In-Reply-To: <tencent_BC34B781C034113F1D56399DF8E0D05BCE09@qq.com>

Quoting Zhao Zhili (2023-12-19 16:37:01)
> From: Zhao Zhili <zhilizhao@tencent.com>
> 
> In close_output(), a dummy frame is created with format NONE passed
> to enc_open(), which doesn't prepare for it. The NULL pointer
> dereference happened at
> av_pix_fmt_desc_get(enc_ctx->pix_fmt)->comp[0].depth.
> 
> When fgt.graph is NULL, skip fg_output_frame() since there is
> nothing to output.
> 
> frame #0: 0x0000005555bc34a4 ffmpeg_g`enc_open(opaque=0xb400007efe2db690, frame=0xb400007efe2d9f70) at ffmpeg_enc.c:235:44
> frame #1: 0x0000005555bef250 ffmpeg_g`enc_open(sch=0xb400007dde2d4090, enc=0xb400007e4e2daad0, frame=0xb400007efe2d9f70) at ffmpeg_sched.c:1462:11
> frame #2: 0x0000005555bee094 ffmpeg_g`send_to_enc(sch=0xb400007dde2d4090, enc=0xb400007e4e2daad0, frame=0xb400007efe2d9f70) at ffmpeg_sched.c:1571:19
> frame #3: 0x0000005555bee01c ffmpeg_g`sch_filter_send(sch=0xb400007dde2d4090, fg_idx=0, out_idx=0, frame=0xb400007efe2d9f70) at ffmpeg_sched.c:2154:12
> frame #4: 0x0000005555bcf124 ffmpeg_g`close_output(ofp=0xb400007e4e2d85b0, fgt=0x0000007d1790eb08) at ffmpeg_filter.c:2225:15
> frame #5: 0x0000005555bcb000 ffmpeg_g`fg_output_frame(ofp=0xb400007e4e2d85b0, fgt=0x0000007d1790eb08, frame=0x0000000000000000) at ffmpeg_filter.c:2317:16
> frame #6: 0x0000005555bc7e48 ffmpeg_g`filter_thread(arg=0xb400007eae2ce7a0) at ffmpeg_filter.c:2836:15
> frame #7: 0x0000005555bee568 ffmpeg_g`task_wrapper(arg=0xb400007d8e2db478) at ffmpeg_sched.c:2200:21
> ---
>  fftools/ffmpeg_filter.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
> index 9fc877b437..69a49a071e 100644
> --- a/fftools/ffmpeg_filter.c
> +++ b/fftools/ffmpeg_filter.c
> @@ -2335,10 +2335,7 @@ static int fg_output_step(OutputFilterPriv *ofp, FilterGraphThread *fgt,
>  
>      ret = av_buffersink_get_frame_flags(filter, frame,
>                                          AV_BUFFERSINK_FLAG_NO_REQUEST);
> -    if (ret == AVERROR_EOF && !fgt->eof_out[ofp->index]) {
> -        ret = fg_output_frame(ofp, fgt, NULL);
> -        return (ret < 0) ? ret : 1;

Why are you removing this block?

-- 
Anton Khirnov
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