> 2021年12月3日 下午8:06，Yy <young_chel...@163.com> 写道： > > > >> 2021年12月3日 下午5:42，Andreas Rheinhardt <andreas.rheinha...@outlook.com >> <mailto:andreas.rheinha...@outlook.com>> 写道： >> >> Yu Yang: >>> Opts is assigned by setup_find_stream_info_opts(). Opts may be NULL. >>> This situation is compatible in avformat_find_stream_info(). >>> Before av_dict_free(), the necessary checks were ignored. >>> >>> // in fftools/ffmpeg_opt.c:1266 >>> 1067 static int open_input_file(OptionsContext *o, const char *filename) >>> 1068 { >>> ... >>> 1191 AVDictionary **opts = setup_find_stream_info_opts(ic, >>> o->g->codec_opts); >>> ... >>> 1196 ret = avformat_find_stream_info(ic, opts); >>> 1197 >>> 1198 for (i = 0; i < orig_nb_streams; i++) >>> 1199 av_dict_free(&opts[i]); >>> ... >>> 1342 } >>> ``` >>> ```c >>> // in libavutil/dict.c:203 >>> 203 void av_dict_free(AVDictionary **pm) >>> 204 { >>> 205 AVDictionary *m = *pm; >>> ... >>> 215 } >>> >>> coredump backtrace info: >>> ==6235==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc >>> 0x000006ba9c2f bp 0x7ffc3d5baa30 sp 0x7ffc3d5ba9a0 T0) >>> ==6235==The signal is caused by a READ memory access. >>> ==6235==Hint: address points to the zero page. >>> #0 0x6ba9c2f in av_dict_free >>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavutil/dict.c:205:23 >>> #1 0x4ce5ac in open_input_file >>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg_opt.c:1199:13 >>> #2 0x4c9dc0 in open_files >>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg_opt.c:3338:15 >>> #3 0x4c9295 in ffmpeg_parse_options >>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg_opt.c:3378:11 >>> #4 0x58f241 in main >>> /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:4988:11 >>> #5 0x7fe35197f0b2 in __libc_start_main >>> /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16 >>> #6 0x42033d in _start (/home/r1/ffmpeg/ffmpeg_4.4.1+0x42033d) >>> >>> Reported-by: TOTE Robot <os...@tsinghua.edu.cn> >>> Signed-off-by: Yu Yang <young_chel...@163.com> >>> --- >>> fftools/ffmpeg_opt.c | 9 +++++---- >>> 1 file changed, 5 insertions(+), 4 deletions(-) >>> >>> diff --git a/fftools/ffmpeg_opt.c b/fftools/ffmpeg_opt.c >>> index a27263b879..a9fc54d948 100644 >>> --- a/fftools/ffmpeg_opt.c >>> +++ b/fftools/ffmpeg_opt.c >>> @@ -1197,10 +1197,11 @@ static int open_input_file(OptionsContext *o, const >>> char *filename) >>> /* If not enough info to get the stream parameters, we decode the >>> first frames to get it. (used in mpeg case for example) */ >>> ret = avformat_find_stream_info(ic, opts); >>> - >>> - for (i = 0; i < orig_nb_streams; i++) >>> - av_dict_free(&opts[i]); >>> - av_freep(&opts); >>> + if (opts){ >>> + for (i = 0; i < orig_nb_streams; i++) >>> + av_dict_free(&opts[i]); >>> + av_freep(&opts); >>> + } >>> >>> if (ret < 0) { >>> av_log(NULL, AV_LOG_FATAL, "%s: could not find codec >>> parameters\n", filename); >>> >> >> You should instead check setup_find_stream_info_opts() (either only call >> it if orig_nb_streams is > 0 or modify it to return an error code given >> that it can currently return NULL even on nonerror). > Thanks for your advice, i will try to fix it again. >> - Andreas Hi, I try to fix this problem lastday and it not work. Today, I refer to your suggestion above to modify. But I think may be you misunderstood this bug. Because of no alloc memory for stream opts, ‘&opts[I]’ free caused crash. And if orig_nb_streams == 0, crash won’t happen. So I think it is unnecessary to fix it call setup_find_stream_info_opts() If orig_nb_streams is > 0. Opts == NULL when orig_nb_streams == 0 or no alloc memory. I don’t think it is error. Because avformat_find_stream_info() allow opts == NULL. But we need to check if opts == NULL before releasing. May be this fix is right? How do you think? Thx. -Yu Yang >> ___________ ____________________________________ >> ffmpeg-devel mailing list >> ffmpeg-devel@ffmpeg.org <mailto:ffmpeg-devel@ffmpeg.org> >> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> <https://ffmpeg.org/mailman/listinfo/ffmpeg-devel> >> >> To unsubscribe, visit link above, or email >> ffmpeg-devel-requ...@ffmpeg.org <mailto:ffmpeg-devel-requ...@ffmpeg.org> >> with subject "unsubscribe".
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