fix: off-by-one heap buffer overread in seekable format - #4758
fix: off-by-one heap buffer overread in seekable format#4758VirajMishra1 wants to merge 2 commits into
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ZSTD_seekTable_getFrameDecompressedSize uses > instead of >= for the frameIndex bounds check, unlike its sister function ZSTD_seekTable_getFrameCompressedSize which correctly uses >=. When frameIndex == tableLen, the function accesses entries[tableLen + 1], reading past the allocated array (numFrames + 1 entries, valid indices 0..numFrames). This is a heap buffer overread. Fix: change > to >= to match getFrameCompressedSize.
Add --stream-size flag to pzstd, matching the existing flag in the main zstd CLI. When compressing from stdin/pipe, this tells the compressor the total input size, enabling it to write the content size in the frame header and optimize window size for better compression ratios. Closes facebook#3171 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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ZSTD_seekTable_getFrameDecompressedSizeincontrib/seekable_format/zstdseek_decompress.cuses>instead of>=for theframeIndexbounds check (line 369), unlike its sister functionZSTD_seekTable_getFrameCompressedSizewhich correctly uses>=(line 357).When
frameIndex == tableLen, the function does not return an error and proceeds to accessentries[frameIndex + 1]. The seek table allocatesnumFrames + 1entries, so valid indices are0..numFrames. IndexnumFrames + 1is a heap buffer overread of uninitialized memory.Any application iterating with
for (i = 0; i <= numFrames; i++)and callinggetFrameDecompressedSizewill silently read past the array. The compressed-size variant catches this; the decompressed-size variant does not.Fix: change
>to>=on line 369, matchinggetFrameCompressedSize.Test: added Test 6 in
contrib/seekable_format/tests/seekable_tests.casserting both functions return errors forframeIndex == nbFrames. All 6 tests pass.