[3.14] gh-156002: Bound zipfile decompression for bzip2/LZMA/Zstandard (GH-156003) (GH-156362) - #156737
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[3.14] gh-156002: Bound zipfile decompression for bzip2/LZMA/Zstandard (GH-156003) (GH-156362)#156737miss-islington wants to merge 1 commit into
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…tandard (pythonGH-156003) (pythonGH-156362) Patch by @tonghuaroot. zipfile.ZipExtFile._read1() bounds the output of each decompress() call for DEFLATE members by passing a max_length to zlib, but for bzip2, LZMA, and Zstandard members it called decompress() with no bound. A whole compressed chunk was therefore expanded into a single allocation before the data[:self._left] clip ran, so a consumer that deliberately reads in small chunks to limit memory (for example zf.open(name).read(8192)) was silently unprotected for non-DEFLATE members. A small, spec-conformant archive member declaring a large uncompressed size could drive multi-GB peak memory. _read1() now passes a per-call bound to the non-DEFLATE decompress() (mirroring the DEFLATE branch) and drains the decompressor's internal buffer across calls by checking needs_input before reading more compressed input. zipfile's LZMADecompressor wrapper forwards max_length and exposes needs_input so the bound also holds for LZMA members. (cherry picked from commit f897dbf) (cherry picked from commit 1b424c0) Co-authored-by: Petr Viktorin <encukou@gmail.com> Co-authored-by: tonghuaroot <tonghuaroot@gmail.com>
This was referenced Aug 31, 2026
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Patch by @tonghuaroot.
zipfile.ZipExtFile._read1() bounds the output of each decompress() call
for DEFLATE members by passing a max_length to zlib, but for bzip2, LZMA,
and Zstandard members it called decompress() with no bound. A whole
compressed chunk was therefore expanded into a single allocation before
the data[:self._left] clip ran, so a consumer that deliberately reads in
small chunks to limit memory (for example zf.open(name).read(8192)) was
silently unprotected for non-DEFLATE members. A small, spec-conformant
archive member declaring a large uncompressed size could drive multi-GB
peak memory.
_read1() now passes a per-call bound to the non-DEFLATE decompress()
(mirroring the DEFLATE branch) and drains the decompressor's internal
buffer across calls by checking needs_input before reading more
compressed input. zipfile's LZMADecompressor wrapper forwards max_length
and exposes needs_input so the bound also holds for LZMA members.
(cherry picked from commit f897dbf)
(cherry picked from commit 1b424c0)
Co-authored-by: Petr Viktorin encukou@gmail.com
Co-authored-by: tonghuaroot tonghuaroot@gmail.com