UBUNTU-CVE-2026-80892: Medium severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: erofs: cap LZMA stream pool size fs/erofs/decompressorlzma.c sizes the module-global MicroLZMA stream pool from numpossiblecpus() when the lzmastreams module parameter is unset, then zerofsloadlzmaconfig() 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 CONFIGEROFSFSZIPLZMADEFAULTMAXSTREAMS 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 lzmastreams module parameter is still honoured as-is, so administrators who deliberately size the pool are not affected.