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`tiffcp` output changes per run (even the size). MemorySanitizer: use-of-uninitialized-value in libtiff/tif_packbits.c:86

Summary

For the given input, tiffcp would emit different results per run.

MemorySanitizer reports:

==3156679==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x6d1c34 in PackBitsEncode /libtiff/repo/clang13-mem-O0/libtiff/tif_packbits.c:86:3
    #1 0x6d3cd4 in PackBitsEncodeChunk /libtiff/repo/clang13-mem-O0/libtiff/tif_packbits.c:205:7
    #2 0x5d96c1 in TIFFWriteEncodedTile /libtiff/repo/clang13-mem-O0/libtiff/tif_write.c:481:10
    #3 0x5d7477 in TIFFWriteTile /libtiff/repo/clang13-mem-O0/libtiff/tif_write.c:373:10
    #4 0x4b0784 in writeBufferToContigTiles /libtiff/repo/clang13-mem-O0/tools/tiffcp.c:1737:8
    #5 0x4af5c7 in cpImage /libtiff/repo/clang13-mem-O0/tools/tiffcp.c:1420:14
    #6 0x4a8f03 in cpContigStrips2ContigTiles /libtiff/repo/clang13-mem-O0/tools/tiffcp.c:1835:9
    #7 0x4a443b in tiffcp /libtiff/repo/clang13-mem-O0/tools/tiffcp.c:979:15
    #8 0x49d6bc in main /libtiff/repo/clang13-mem-O0/tools/tiffcp.c:334:9
    #9 0x7fa1472a30b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
    #10 0x41d6bd in _start (/shared/targets/libtiff/repo/clang13-mem-O0/tools/tiffcp+0x41d6bd)

SUMMARY: MemorySanitizer: use-of-uninitialized-value /libtiff/repo/clang13-mem-O0/libtiff/tif_packbits.c:86:3 in PackBitsEncode

Version

libtiff 4.3.0 (commit 4002ca1c)

Steps to reproduce

  • Run tiffcp -i -c packbits issue- tmp.out a few times and you'll observe that the content of tmp.out is changing.
  • Compile with -fsanitize=memory if you wish to see MemorySanitizer report.
  • issue-375

Platform

Ubuntu 20.04.4 LTS, x86_64