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[77.56.209.237]) by smtp.gmail.com with ESMTPSA id a184sm1475444wmf.29.2020.03.03.17.55.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Mar 2020 17:55:33 -0800 (PST) From: KP Singh To: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , Paul Turner , Jann Horn , Florent Revest , Brendan Jackman Subject: [PATCH bpf-next v2 0/7] Introduce BPF_MODIFY_RET tracing progs Date: Wed, 4 Mar 2020 02:55:21 +0100 Message-Id: <20200304015528.29661-1-kpsingh@chromium.org> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org From: KP Singh v1 -> v2: * Adressed Andrii's feedback. * Fixed a bug that Alexei noticed about nop generation. * Rebase. This was brought up in the KRSI v4 discussion and found to be useful both for security and tracing programs. https://lore.kernel.org/bpf/20200225193108.GB22391@chromium.org/ The modify_return programs are allowed for security hooks (with an extra CAP_MAC_ADMIN check) and functions whitelisted for error injection (ALLOW_ERROR_INJECTION). The "security_" check is expected to be cleaned up with the KRSI patch series. Here is an example of how a fmod_ret program behaves: int func_to_be_attached(int a, int b) { <--- do_fentry do_fmod_ret: if (ret != 0) goto do_fexit; original_function: } <--- do_fexit ALLOW_ERROR_INJECTION(func_to_be_attached, ERRNO) The fmod_ret program attached to this function can be defined as: SEC("fmod_ret/func_to_be_attached") int BPF_PROG(func_name, int a, int b, int ret) { // This will skip the original function logic. return -1; } KP Singh (7): bpf: Refactor trampoline update code bpf: JIT helpers for fmod_ret progs bpf: Introduce BPF_MODIFY_RETURN bpf: Attachment verification for BPF_MODIFY_RETURN tools/libbpf: Add support for BPF_MODIFY_RETURN bpf: Add test ops for BPF_PROG_TYPE_TRACING bpf: Add selftests for BPF_MODIFY_RETURN arch/x86/net/bpf_jit_comp.c | 279 +++++++++++++----- include/linux/bpf.h | 24 +- include/uapi/linux/bpf.h | 1 + kernel/bpf/bpf_struct_ops.c | 12 +- kernel/bpf/btf.c | 27 +- kernel/bpf/syscall.c | 1 + kernel/bpf/trampoline.c | 65 ++-- kernel/bpf/verifier.c | 32 ++ kernel/trace/bpf_trace.c | 1 + net/bpf/test_run.c | 57 +++- tools/include/uapi/linux/bpf.h | 1 + tools/lib/bpf/libbpf.c | 4 + .../selftests/bpf/prog_tests/fentry_fexit.c | 12 +- .../selftests/bpf/prog_tests/fentry_test.c | 14 +- .../selftests/bpf/prog_tests/fexit_test.c | 69 ++--- .../selftests/bpf/prog_tests/modify_return.c | 65 ++++ .../selftests/bpf/progs/modify_return.c | 49 +++ 17 files changed, 526 insertions(+), 187 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/modify_return.c create mode 100644 tools/testing/selftests/bpf/progs/modify_return.c