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[104.199.75.203]) by smtp.gmail.com with ESMTPSA id m3sm20783212wrv.6.2020.11.16.15.25.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Nov 2020 15:25:37 -0800 (PST) From: KP Singh To: linux-kernel@vger.kernel.org, bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , Florent Revest , Brendan Jackman , Pauline Middelink Subject: [PATCH bpf-next v2 1/2] bpf: Add bpf_lsm_set_bprm_opts helper Date: Mon, 16 Nov 2020 23:25:35 +0000 Message-Id: <20201116232536.1752908-1-kpsingh@chromium.org> X-Mailer: git-send-email 2.29.2.299.gdc1121823c-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: KP Singh The helper allows modification of certain bits on the linux_binprm struct starting with the secureexec bit which can be updated using the BPF_LSM_F_BPRM_SECUREEXEC flag. secureexec can be set by the LSM for privilege gaining executions to set the AT_SECURE auxv for glibc. When set, the dynamic linker disables the use of certain environment variables (like LD_PRELOAD). Signed-off-by: KP Singh --- include/uapi/linux/bpf.h | 14 ++++++++++++++ kernel/bpf/bpf_lsm.c | 27 +++++++++++++++++++++++++++ scripts/bpf_helpers_doc.py | 2 ++ tools/include/uapi/linux/bpf.h | 14 ++++++++++++++ 4 files changed, 57 insertions(+) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 162999b12790..7f1b6ba8246c 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3787,6 +3787,14 @@ union bpf_attr { * *ARG_PTR_TO_BTF_ID* of type *task_struct*. * Return * Pointer to the current task. + * + * long bpf_lsm_set_bprm_opts(struct linux_binprm *bprm, u64 flags) + * + * Description + * Sets certain options on the *bprm*: + * + * **BPF_LSM_F_BPRM_SECUREEXEC** Set the secureexec bit + * which sets the **AT_SECURE** auxv for glibc. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -3948,6 +3956,7 @@ union bpf_attr { FN(task_storage_get), \ FN(task_storage_delete), \ FN(get_current_task_btf), \ + FN(lsm_set_bprm_opts), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper @@ -4119,6 +4128,11 @@ enum bpf_lwt_encap_mode { BPF_LWT_ENCAP_IP, }; +/* Flags for LSM helpers */ +enum { + BPF_LSM_F_BPRM_SECUREEXEC = (1ULL << 0), +}; + #define __bpf_md_ptr(type, name) \ union { \ type name; \ diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index 553107f4706a..31f85474a0ef 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include #include @@ -51,6 +52,30 @@ int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog, return 0; } +/* Mask for all the currently supported BPRM option flags */ +#define BPF_LSM_F_BRPM_OPTS_MASK 0x1ULL + +BPF_CALL_2(bpf_lsm_set_bprm_opts, struct linux_binprm *, bprm, u64, flags) +{ + + if (flags & ~BPF_LSM_F_BRPM_OPTS_MASK) + return -EINVAL; + + bprm->secureexec = (flags & BPF_LSM_F_BPRM_SECUREEXEC); + return 0; +} + +BTF_ID_LIST_SINGLE(bpf_lsm_set_bprm_opts_btf_ids, struct, linux_binprm) + +const static struct bpf_func_proto bpf_lsm_set_bprm_opts_proto = { + .func = bpf_lsm_set_bprm_opts, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_BTF_ID, + .arg1_btf_id = &bpf_lsm_set_bprm_opts_btf_ids[0], + .arg2_type = ARG_ANYTHING, +}; + static const struct bpf_func_proto * bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { @@ -71,6 +96,8 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_task_storage_get_proto; case BPF_FUNC_task_storage_delete: return &bpf_task_storage_delete_proto; + case BPF_FUNC_lsm_set_bprm_opts: + return &bpf_lsm_set_bprm_opts_proto; default: return tracing_prog_func_proto(func_id, prog); } diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py index 31484377b8b1..c5bc947a70ad 100755 --- a/scripts/bpf_helpers_doc.py +++ b/scripts/bpf_helpers_doc.py @@ -418,6 +418,7 @@ class PrinterHelpers(Printer): 'struct bpf_tcp_sock', 'struct bpf_tunnel_key', 'struct bpf_xfrm_state', + 'struct linux_binprm', 'struct pt_regs', 'struct sk_reuseport_md', 'struct sockaddr', @@ -465,6 +466,7 @@ class PrinterHelpers(Printer): 'struct bpf_tcp_sock', 'struct bpf_tunnel_key', 'struct bpf_xfrm_state', + 'struct linux_binprm', 'struct pt_regs', 'struct sk_reuseport_md', 'struct sockaddr', diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 162999b12790..7f1b6ba8246c 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -3787,6 +3787,14 @@ union bpf_attr { * *ARG_PTR_TO_BTF_ID* of type *task_struct*. * Return * Pointer to the current task. + * + * long bpf_lsm_set_bprm_opts(struct linux_binprm *bprm, u64 flags) + * + * Description + * Sets certain options on the *bprm*: + * + * **BPF_LSM_F_BPRM_SECUREEXEC** Set the secureexec bit + * which sets the **AT_SECURE** auxv for glibc. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -3948,6 +3956,7 @@ union bpf_attr { FN(task_storage_get), \ FN(task_storage_delete), \ FN(get_current_task_btf), \ + FN(lsm_set_bprm_opts), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper @@ -4119,6 +4128,11 @@ enum bpf_lwt_encap_mode { BPF_LWT_ENCAP_IP, }; +/* Flags for LSM helpers */ +enum { + BPF_LSM_F_BPRM_SECUREEXEC = (1ULL << 0), +}; + #define __bpf_md_ptr(type, name) \ union { \ type name; \