CVE-2026-80892erofs: cap LZMA stream pool size

Official description

In the Linux kernel, the following vulnerability has been resolved: erofs: cap LZMA stream pool size fs/erofs/decompressor_lzma.c sizes the module-global MicroLZMA stream pool from num_possible_cpus() when the lzma_streams module parameter is unset, then z_erofs_load_lzma_config() preallocates one image-supplied dictionary per stream, accepting dictionaries up to 8 MiB. On high-CPU systems, a small EROFS image can pin hundreds of MiB of vmalloc-backed decoder state until the erofs module is unloaded. Impact: An EROFS image mounted by the system can pin up to 8 MiB of vmalloc memory per LZMA stream, either as intended or unexpectedly. Bound the default stream count by a new CONFIG_EROFS_FS_ZIP_LZMA_DEFAULT_MAX_STREAMS option, default 16, so the worst-case default preallocation is 128 MiB if the number of CPUs is no less than 16 while preserving the existing per-image dictionary limit. An explicit lzma_streams module parameter is still honoured as-is, so administrators who deliberately size the pool are not affected.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/682cb3ece37fc5141e73bc726ccf4adb833e5189
• https://git.kernel.org/stable/c/e8b3d09aa8889dda9be9cbb3d2f0218c4b9acde4
• https://git.kernel.org/stable/c/0c676903cb2a61992ded8e7907609cc6b0f11744
• https://git.kernel.org/stable/c/5aaa06dfc10f8398c8807453dbec738ea9af10e4
• https://git.kernel.org/stable/c/e52da169b8c0d19bb2d803f2a07fe0e5a00462d6
• https://git.kernel.org/stable/c/c9b47e6b23114e939b17f818471c7a46e59006e7