left shift of negative value at libswscale/output.c:2114

[Suhwan]

Summary of the bug:
There're two left shift of negative value at libswscale/output.c

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 despill -loglevel 0 -c jpeg2000 tmp.scc

ffmpeg version N-95517-g0b8956b25c 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:2114:54: runtime error: left shift of negative value -1536

Thread 1 "ffmpeg_g" hit Breakpoint 1, 0x00000000004288b0 in __ubsan::ScopedReport::~ScopedReport() ()
(gdb) bt
#0  0x00000000004288b0 in __ubsan::ScopedReport::~ScopedReport() ()
#1  0x000000000042a9a0 in handleShiftOutOfBoundsImpl(__ubsan::ShiftOutOfBoundsData*, unsigned long, unsigned long, __ubsan::ReportOptions) ()
#2  0x000000000042cb41 in __ubsan_handle_shift_out_of_bounds ()
#3  0x0000000005676001 in yuv2rgb_full_1_c_template (c=0x9435d80, buf0=<optimized out>, ubuf=<optimized out>, 
    vbuf=<optimized out>, abuf0=<optimized out>, dest=<optimized out>, dstW=455, uvalpha=3087, y=2, target=AV_PIX_FMT_ARGB, 
    hasAlpha=0) at libswscale/output.c:2114
#4  yuv2xrgb32_full_1_c (c=0x9435d80, buf0=<optimized out>, ubuf=<optimized out>, vbuf=<optimized out>, 
    abuf0=<optimized out>, dest=<optimized out>, dstW=455, uvalpha=3087, y=2) at libswscale/output.c:2148
#5  0x000000000556297c in packed_vscale (c=<optimized out>, desc=<optimized out>, sliceY=<optimized out>, 
    sliceH=<optimized out>) at libswscale/vscale.c:134
#6  0x0000000005529255 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
#7  0x00000000055337c2 in sws_scale (c=0x9435d80, srcSlice=0x943fa74, srcStride=0x7fffffffc190, srcSliceY=0, srcSliceH=341, 
    dst=<optimized out>, dstStride=0x7fffffffc180) at libswscale/swscale.c:978
#8  0x0000000000d361ee 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
#9  0x0000000000d31c9d in scale_frame (link=<optimized out>, in=0x946bf00, frame_out=<optimized out>)
    at libavfilter/vf_scale.c:535
#10 0x0000000000d2f20d in filter_frame (link=0x9431040, in=0x946bf00) at libavfilter/vf_scale.c:549
#11 0x00000000005d002d in ff_filter_frame_framed (link=<optimized out>, frame=0x0) at libavfilter/avfilter.c:1084
#12 ff_filter_frame_to_filter (link=<optimized out>) at libavfilter/avfilter.c:1232
#13 ff_filter_activate_default (filter=<optimized out>) at libavfilter/avfilter.c:1281
#14 ff_filter_activate (filter=<optimized out>) at libavfilter/avfilter.c:1443
#15 0x00000000005f4435 in push_frame (graph=0x93e2040) at libavfilter/buffersrc.c:187
#16 av_buffersrc_add_frame_internal (ctx=<optimized out>, frame=0x93d0200, flags=<optimized out>)
    at libavfilter/buffersrc.c:261
#17 0x00000000005f300e in av_buffersrc_add_frame_flags (ctx=0x94302c0, frame=0x93d0200, flags=4)
    at libavfilter/buffersrc.c:170
#18 0x00000000004cad80 in ifilter_send_frame (ifilter=<optimized out>, frame=<optimized out>) at fftools/ffmpeg.c:2186
#19 send_frame_to_filters (ist=0x93cad80, decoded_frame=0x93d0200) at fftools/ffmpeg.c:2260
#20 0x00000000004a07dc in decode_video (ist=<optimized out>, pkt=<optimized out>, got_output=<optimized out>, 
    duration_pts=<optimized out>, eof=<optimized out>, decode_failed=<optimized out>) at fftools/ffmpeg.c:2459
#21 process_input_packet (ist=<optimized out>, pkt=<optimized out>, no_eof=<optimized out>) at fftools/ffmpeg.c:2613
#22 0x00000000004bf110 in process_input (file_index=<optimized out>) at fftools/ffmpeg.c:4508
#23 0x000000000048d60b in transcode_step () at fftools/ffmpeg.c:4628
#24 transcode () at fftools/ffmpeg.c:4682
#25 0x0000000000487dc4 in main (argc=11, argv=<optimized out>) at fftools/ffmpeg.c:4884
(gdb) c
Continuing.
libswscale/output.c:2115:54: runtime error: left shift of negative value -89

Thread 1 "ffmpeg_g" hit Breakpoint 1, 0x00000000004288b0 in __ubsan::ScopedReport::~ScopedReport() ()
(gdb) q

Please confirm.
Thanks

[Suhwan]

poc

[Carl Eugen Hoyos]

Fixed by Michael in 7b7f97532b2ac8836d8d8e3c71dd026e35ae1ca7