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mirror_zfs/module/zstd
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Alexander Moch e7f9734bc7 Zstd: Fix ASan poisoning for pooled Zstd contexts 
The Zstd context mempool can reuse buffers that were previously poisoned
under AddressSanitizer, leading to false-positive use-after-poison reports
during zloop and other stress tests.

Explicitly unpoison memory when handing buffers out to Zstd and poison the
user-visible region again when buffers are returned to the pool. This makes
the allocator ASan-correct while preserving existing pooling behavior.

Also fix non-standard void * pointer arithmetic in zstd_free() and remove an
early return in zstd_dctx_alloc() so kmem_type/kmem_size are always set on
pool hits.

This only affects ASan bookkeeping in user space, does not change runtime
behavior in non-ASan configurations, and does not affect on-disk formats.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alexander Moch <mail@alexmoch.com>
Closes #18089
2026-01-20 13:41:12 -08:00
..
include Zstd: Integrate v1.5.7 into the ZFS build system 2026-01-20 13:41:06 -08:00
lib Zstd: Integrate v1.5.7 into the ZFS build system 2026-01-20 13:41:06 -08:00
README.md linux: module: weld all but spl.ko into zfs.ko 2022-04-20 13:28:24 -07:00
zfs_zstd.c Zstd: Fix ASan poisoning for pooled Zstd contexts 2026-01-20 13:41:12 -08:00
zstd_sparc.c Fix cross-endian interoperability of zstd 2021-08-30 14:13:46 -07:00
zstd-in.c Zstd: Update bundled library to v1.5.7 without further adjustments 2026-01-20 13:40:37 -08:00

README.md

ZSTD-On-ZFS Library Manual

Introduction

This subtree contains the ZSTD library used in ZFS. It is heavily cut-down by dropping any unneeded files, and combined into a single file, but otherwise is intentionally unmodified. Please do not alter the file containing the zstd library, besides upgrading to a newer ZSTD release.

Tree structure:

  • zfs_zstd.c are the actual zfs kernel module hooks.
  • lib/ contains the unmodified version of the Zstandard library
  • zstd-in.c is our template file for generating the single-file library
  • include/: This directory contains supplemental includes for platform compatibility, which are not expected to be used by ZFS elsewhere in the future. Thus we keep them private to ZSTD.

Updating ZSTD

To update ZSTD the following steps need to be taken:

  1. Grab the latest release of ZSTD.
  2. Copy the files output by the following script to module/zstd/lib/: grep include [path to zstd]/contrib/single_file_libs/zstd-in.c | awk '{ print $2 }'
  3. Remove debug.c, threading.c, and zstdmt_compress.c.
  4. Update Makefiles with resulting file lists.
  5. Follow symbol renaming notes in include/zstd_compat_wrapper.h

Altering ZSTD and breaking changes

If ZSTD made changes that break compatibility or you need to make breaking changes to the way we handle ZSTD, it is required to maintain backwards compatibility.

We already save the ZSTD version number within the block header to be used to add future compatibility checks and/or fixes. However, currently it is not actually used in such a way.