signed integer overflow at libswscale/output.c:1852

[Suhwan]

Summary of the bug:
There is a signed integer overflow at libswscale/output.c:1852

I compiled ffmpeg with "--toolchain=clang-usan" to check the undefined-behaviours and attached log file.
How to reproduce:

% ffmpeg_g -y -i $PoC -filter_complex allyuv -loglevel 0 -map 0 tmp.afc

ffmpeg version N-95405-g98ae6b0a4d Copyright (c) 2000-2019 the FFmpeg developers
built with clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)
configuration: --cc=clang --cxx=clang++ --ld=clang --enable-debug --toolchain=clang-usan

Here's UBSAN log

libswscale/output.c:1852:11: runtime error: signed integer overflow: 1169365504 + 981452800 cannot be represented in type 'int'

Thread 1 "ffmpeg_g" hit Breakpoint 1, 0x00000000004288b0 in __ubsan::ScopedReport::~ScopedReport() ()
(gdb) bt
#0  0x00000000004288b0 in __ubsan::ScopedReport::~ScopedReport() ()
#1  0x000000000042b0eb in void handleIntegerOverflowImpl<__ubsan::Value>(__ubsan::OverflowData*, unsigned long, char const*, __ubsan::Value, __ubsan::ReportOptions) ()
#2  0x000000000042c8bf in __ubsan_handle_add_overflow ()
#3  0x00000000056a35f4 in yuv2rgb_write_full (c=<optimized out>, Y=1169365504, A=0, U=<optimized out>, V=<optimized out>, target=AV_PIX_FMT_RGB24, hasAlpha=0, dest=<optimized out>, 
    i=<optimized out>, y=<optimized out>, err=<optimized out>) at libswscale/output.c:1852
#4  yuv2rgb_full_1_c_template (c=<optimized out>, buf0=<optimized out>, ubuf=<optimized out>, vbuf=<optimized out>, abuf0=<optimized out>, dest=<optimized out>, dstW=<optimized out>, 
    uvalpha=<optimized out>, y=<optimized out>, target=AV_PIX_FMT_RGB24, hasAlpha=0) at libswscale/output.c:2103
#5  yuv2rgb24_full_1_c (c=0x93f0880, buf0=<optimized out>, ubuf=<optimized out>, vbuf=<optimized out>, abuf0=<optimized out>, dest=<optimized out>, dstW=4096, uvalpha=0, y=4)
    at libswscale/output.c:2148
#6  0x000000000554d1fc in packed_vscale (c=<optimized out>, desc=<optimized out>, sliceY=<optimized out>, sliceH=<optimized out>) at libswscale/vscale.c:128
#7  0x0000000005516445 in swscale (c=<optimized out>, src=<optimized out>, srcStride=<optimized out>, srcSliceY=<optimized out>, srcSliceH=<optimized out>, dst=<optimized out>, 
    dstStride=<optimized out>) at libswscale/swscale.c:503
#8  0x00000000055209b2 in sws_scale (c=0x93f0880, srcSlice=0x93fa574, srcStride=0x7fffffffc9a0, srcSliceY=0, srcSliceH=4096, dst=<optimized out>, dstStride=0x7fffffffc990)
    at libswscale/swscale.c:978
#9  0x0000000000d247ce in scale_slice (link=<optimized out>, out_buf=<optimized out>, cur_pic=<optimized out>, sws=<optimized out>, y=<optimized out>, h=<optimized out>, mul=<optimized out>, 
    field=<optimized out>) at libavfilter/vf_scale.c:411
#10 0x0000000000d2027d in scale_frame (link=<optimized out>, in=0xa19f240, frame_out=<optimized out>) at libavfilter/vf_scale.c:535
#11 0x0000000000d1d7ed in filter_frame (link=0x93ed9c0, in=0xa19f240) at libavfilter/vf_scale.c:549
#12 0x00000000005cfe9d in ff_filter_frame_framed (link=<optimized out>, frame=0x0) at libavfilter/avfilter.c:1084
#13 ff_filter_frame_to_filter (link=<optimized out>) at libavfilter/avfilter.c:1232
#14 ff_filter_activate_default (filter=<optimized out>) at libavfilter/avfilter.c:1281
#15 ff_filter_activate (filter=<optimized out>) at libavfilter/avfilter.c:1443
#16 0x00000000005eecd3 in get_frame_internal (ctx=0x93ed440, frame=<optimized out>, flags=1, samples=<optimized out>) at libavfilter/buffersink.c:110
#17 0x00000000005e254b in avfilter_graph_request_oldest (graph=0x93e0b00) at libavfilter/avfiltergraph.c:1409
#18 0x000000000048c3a2 in transcode_from_filter (graph=0x93ae700, best_ist=<optimized out>) at fftools/ffmpeg.c:4531
#19 transcode_step () at fftools/ffmpeg.c:4606
#20 transcode () at fftools/ffmpeg.c:4682
#21 0x0000000000487da4 in main (argc=11, argv=<optimized out>) at fftools/ffmpeg.c:4884

Please confirm.
Thanks

[Suhwan]

poc

[Balling]

​https://patchwork.ffmpeg.org/project/ffmpeg/patch/20200216194303.819-3-michael@niedermayer.cc/

[Carl Eugen Hoyos]

Fixed by Michael in e057e83a4ff4c0eeeb78dffe58e21af951c056b6