Security fixes in libfuse-3.18.3
libfuse 3.18.3 disables fuse_session_custom_io() by default to stop non-kernel peers from forging FUSE requests libfuse parses unvalidated.
libfuse 3.18.3 ships security fixes announced by Sam James on the oss-security mailing list. The fuse_session_custom_io() function is now disabled unless libfuse is built with -Denable-custom-io=true, returning -ENOTSUP otherwise. The reason is that a custom io peer might not be a kernel and can forge requests that libfuse parses without validation. The hello_ll_uds example is now built only with that option, and enabling it triggers a warning at configure time.
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