[bpf-next,v4,0/4] Support freplace prog from user namespace

Message

Mykyta Yatsenko March 10, 2025, 12:13 a.m. UTC

From: Mykyta Yatsenko <[e-mail]>

Freplace programs can't be loaded from user namespace, as
bpf_program__set_attach_target() requires searching for target prog BTF,
which is locked under CAP_SYS_ADMIN.
This patch set enables this use case by:
1. Relaxing capable check in bpf's BPF_BTF_GET_FD_BY_ID, check for CAP_BPF
instead of CAP_SYS_ADMIN, support BPF token in attr argument.
2. Pass BPF token around libbpf from bpf_program__set_attach_target() to
bpf syscall where capable check is.
3. Validate positive/negative scenarios in selftests

This patch set is enabled by the recent libbpf change[1], that
introduced bpf_object__prepare() API. Calling bpf_object__prepare() for
freplace program before bpf_program__set_attach_target() initializes BPF
token, which is then passed to bpf syscall by libbpf.

[1] https://lore.kernel.org/all/[e-mail]/

Mykyta Yatsenko (4):
  bpf: BPF token support for BPF_BTF_GET_FD_BY_ID
  bpf: return prog btf_id without capable check
  libbpf: pass BPF token from find_prog_btf_id to BPF_BTF_GET_FD_BY_ID
  selftests/bpf: test freplace from user namespace

 include/uapi/linux/bpf.h                      |  1 +
 kernel/bpf/syscall.c                          | 25 ++++-
 tools/include/uapi/linux/bpf.h                |  1 +
 tools/lib/bpf/bpf.c                           |  3 +-
 tools/lib/bpf/bpf.h                           |  4 +-
 tools/lib/bpf/btf.c                           | 15 ++-
 tools/lib/bpf/libbpf.c                        | 10 +-
 tools/lib/bpf/libbpf_internal.h               |  1 +
 .../bpf/prog_tests/libbpf_get_fd_by_id_opts.c |  3 +-
 .../testing/selftests/bpf/prog_tests/token.c  | 97 ++++++++++++++++++-
 .../selftests/bpf/progs/priv_freplace_prog.c  | 13 +++
 tools/testing/selftests/bpf/progs/priv_prog.c |  6 +-
 12 files changed, 159 insertions(+), 20 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/priv_freplace_prog.c