MFV r268120:
4936 lz4 could theoretically overflow a pointer with a certain input illumos/illumos-gate@58d0718061c87e3d647c891ec5281b93c08dba4e
Reviewed by: delphij
MFC after: 2 weeks
Sponsored by: ScaleEngine Inc.
Differential Revision: https://reviews.freebsd.org/D7850