bpf: allow fs kfuncs for binfmt_misc_ops programs

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The fs kfuncs are currently exclusive to LSM programs. A binfmt_misc
handler needs a subset of them to do anything interesting: computing an
interpreter relative to the binary's location wants bpf_path_d_path()
on bprm->file->f_path from the load program, and matching on per-binary
metadata wants bpf_get_file_xattr() and friends right from the match
program.

Register the fs kfunc set for struct_ops programs as well and extend
the filter to admit binfmt_misc_ops programs. The xattr setters stay
exclusive to LSM programs: a binary type handler decides how to run a
binary, it has no business modifying filesystem state.

This only takes effect in builds that have the fs kfunc set at all,
i.e. CONFIG_BPF_LSM. Without it a binfmt_misc handler is limited to
bprm fields and the file-backed dynptr, which are provided by the
common kfunc set.

Link: https://lore.kernel.org/20260704211409.1978485-1-farid.m.zakaria@gmail.com
Link: https://patch.msgid.link/20260714-work-bpf-binfmt_misc-v2-5-57b7529c002c@kernel.org
Reviewed-by: Farid Zakaria <farid.m.zakaria@gmail.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

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Christian Brauner 2026-07-14 21:58:10 +02:00

parent ceb912149e

commit 7bddf0e9f1

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fs/bpf_fs_kfuncs.c

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