On Windows, mmap sent a shared memory descriptor straight to the shared
file mapper, skipping the checks and the private path that a regular
file descriptor takes. A private mapping of a named or anonymous object
then failed with EOPNOTSUPP, and a writable shared mapping of a
read-only descriptor failed with EIO instead of EACCES. Shared memory
objects are files on Windows, so they now take the same access checks
and the same private copy as a regular file; only the directory, device
and file-type refusals stay limited to other descriptors.
guest_named_shm_windows_mapping covers shared mappings through two
descriptors, pread and pwrite against them, an offset mapping, a private
mapping, read-only mappings and the mappings after shm_unlink.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
