[FFmpeg-devel] [PATCH] libswresample/swresamplec: Err num(negative-size) was used as a function parameter

[Michael Niedermayer]

On Tue, Dec 07, 2021 at 08:12:53PM +0800, Yy wrote:
> 
> 
> > 2021年12月7日 下午7:25，Michael Niedermayer <michael at niedermayer.cc> 写道：
> > 
> > On Mon, Dec 06, 2021 at 08:21:42PM +0800, Yu Yang wrote:
> >> If cannot allocate memory, ERROR(ENOMEM) '-12' as a parameter will be constantly being returned.
> >> When run resample() firstly, negative size param would cause buffer-overflow and SEGV in swri_rematrix(). 
> >> When run swri_rematrix() firstly, resample() would not cause error but Err num as a wrong parameter passing.
> >> Err num should be returned immediately. And remove assert to ensure the return of the error code.
> >> 
> >> coredump info:
> >>    #0 0x499517 in posix_memalign (/home/r1/ffmpeg/ffmpeg_4.4.1+0x499517)
> >>    #1 0x6c1f0b4 in av_malloc /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavutil/mem.c:86:9
> >>    #2 0x6c208fe in av_mallocz /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavutil/mem.c:239:17
> >>    #3 0x6c207ad in av_mallocz_array /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavutil/mem.c:195:12
> >>    #4 0x654b2e5 in swri_realloc_audio /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libswresample/swresample.c:418:14
> >>    #5 0x654f9a1 in swr_convert_internal /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libswresample/swresample.c:601:17
> >>    #6 0x654d2c0 in swr_convert /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libswresample/swresample.c:766:19
> >>    #7 0x186cf56 in flush_frame /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/af_aresample.c:251:13
> >>    #8 0x186a454 in request_frame /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/af_aresample.c:288:20
> >>    #9 0x787d9c in ff_request_frame_to_filter /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfilter.c:459:15
> >>    #10 0x7877f1 in forward_status_change /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfilter.c:1257:19
> >>    #11 0x77ed7e in ff_filter_activate_default /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfilter.c:1288:20
> >>    #12 0x77e4e1 in ff_filter_activate /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfilter.c:1441:11
> >>    #13 0x793b3f in ff_filter_graph_run_once /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfiltergraph.c:1403:12
> >>    #14 0x7a7bee in get_frame_internal /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/buffersink.c:131:19
> >>    #15 0x7a7287 in av_buffersink_get_frame_flags /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/buffersink.c:142:12
> >>    #16 0x792888 in avfilter_graph_request_oldest /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/libavfilter/avfiltergraph.c:1356:17
> >>    #17 0x5d07df in transcode_from_filter /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:4639:11
> >>    #18 0x59e557 in transcode_step /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:4729:20
> >>    #19 0x593970 in transcode /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:4805:15
> >>    #20 0x58f7a4 in main /home/r1/ffmpeg/ffmpeg-4.4.1/build/src/fftools/ffmpeg.c:5010:9
> >>    #21 0x7f6fd2dee0b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
> >> 
> >> SUMMARY: AddressSanitizer: negative-size-param (/home/r1/ffmpeg/ffmpeg_4.4.1+0x497e67) in __asan_memcpy
> >> 
> >> Reported-by: TOTE Robot <oslab at tsinghua.edu.cn>
> >> Signed-off-by: Yu Yang <young_chelsea at 163.com>
> >> ---
> >> libswresample/swresample.c | 6 +++++-
> >> 1 file changed, 5 insertions(+), 1 deletion(-)
> >> 
> >> diff --git a/libswresample/swresample.c b/libswresample/swresample.c
> >> index c03fe5528f..92ab6a9148 100644
> >> --- a/libswresample/swresample.c
> >> +++ b/libswresample/swresample.c
> >> @@ -644,6 +644,8 @@ static int swr_convert_internal(struct SwrContext *s, AudioData *out, int out_co
> >>     if(s->resample_first){
> > 
> >>         if(postin != midbuf)
> >>             out_count= resample(s, midbuf, out_count, postin, in_count);
> >> +            if (out_count < 0)
> >> +                return out_count;
> > 
> > this doesnt look right
> I could not understand your relpy. Do you mean this bug not exist, or this patch not good ? 

The patch looks wrong
Do you see the difference between teh 3 pieces of code below:

if(postin != midbuf)
    out_count= resample(s, midbuf, out_count, postin, in_count);
    if (out_count < 0)
        return out_count;


if(postin != midbuf)
    out_count= resample(s, midbuf, out_count, postin, in_count);
if (out_count < 0)
    return out_count;
        

if(postin != midbuf) {
    out_count= resample(s, midbuf, out_count, postin, in_count);
    if (out_count < 0)
        return out_count;
}
        
        
[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Its not that you shouldnt use gotos but rather that you should write
readable code and code with gotos often but not always is less readable
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