Unprivileged BPF disabled (kernel.unprivileged_bpf_disabled >= 1) is the default in most cases now; when set, the BPF system call is blocked for users without CAP_BPF/CAP_SYS_ADMIN. In some cases however, it makes sense to split activities between capability-requiring ones - such as program load/attach - and those that might not require capabilities such as reading perf/ringbuf events, reading or updating BPF map configuration etc. One example of this sort of approach is a service that loads a BPF program, and a user-space program that interacts with it. Here - rather than blocking all BPF syscall commands - unprivileged BPF disabled blocks the key object-creating commands (prog load, map load). Discussion has alluded to this idea in the past [1], and Alexei mentioned it was also discussed at LSF/MM/BPF this year. Changes since v3 [2]: - added acks to patch 1 - CI was failing on Ubuntu; I suspect the issue was an old capability.h file which specified CAP_LAST_CAP as < CAP_BPF, leading to the logic disabling all caps not disabling CAP_BPF. Use CAP_BPF as basis for "all caps" bitmap instead as we explicitly define it in cap_helpers.h if not already found in capabilities.h - made global variables arguments to subtests instead (Andrii, patch 2) Changes since v2 [3]: - added acks from Yonghong - clang compilation issue in selftest with bpf_prog_query() (Alexei, patch 2) - disable all capabilities for test (Yonghong, patch 2) - add assertions that size of perf/ringbuf data matches expectations (Yonghong, patch 2) - add map array size definition, remove unneeded whitespace (Yonghong, patch 2) Changes since RFC [4]: - widened scope of commands unprivileged BPF disabled allows (Alexei, patch 1) - removed restrictions on map types for lookup, update, delete (Alexei, patch 1) - removed kernel CONFIG parameter controlling unprivileged bpf disabled change (Alexei, patch 1) - widened test scope to cover most BPF syscall commands, with positive and negative subtests [1] https://lore.kernel.org/bpf/CAADnVQLTBhCTAx1a_nev7CgMZxv1Bb7ecz1AFRin8tHmjPREJA@xxxxxxxxxxxxxx/ [2] https://lore.kernel.org/bpf/1652880861-27373-1-git-send-email-alan.maguire@xxxxxxxxxx/T/ [3] https://lore.kernel.org/bpf/1652788780-25520-1-git-send-email-alan.maguire@xxxxxxxxxx/T/#t [4] https://lore.kernel.org/bpf/20220511163604.5kuczj6jx3ec5qv6@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/T/#mae65f35a193279e718f37686da636094d69b96ee Alan Maguire (2): bpf: refine kernel.unprivileged_bpf_disabled behaviour selftests/bpf: add tests verifying unprivileged bpf behaviour kernel/bpf/syscall.c | 14 +- .../bpf/prog_tests/unpriv_bpf_disabled.c | 312 ++++++++++++++++++ .../bpf/progs/test_unpriv_bpf_disabled.c | 83 +++++ 3 files changed, 408 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/unpriv_bpf_disabled.c create mode 100644 tools/testing/selftests/bpf/progs/test_unpriv_bpf_disabled.c -- 2.27.0
