From patchwork Fri Mar 27 19:28:50 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: KP Singh X-Patchwork-Id: 11463013 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9A6D41667 for ; Fri, 27 Mar 2020 19:29:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 64F43206E6 for ; Fri, 27 Mar 2020 19:29:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="LPV+4eg7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727831AbgC0T3F (ORCPT ); Fri, 27 Mar 2020 15:29:05 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:38885 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727781AbgC0T3E (ORCPT ); Fri, 27 Mar 2020 15:29:04 -0400 Received: by mail-wm1-f67.google.com with SMTP id f6so7078056wmj.3 for ; Fri, 27 Mar 2020 12:29:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=7acCzk1+zYOdikz1rYM+I9HTPn/mSo41yDTPsye6fPA=; b=LPV+4eg7XLxPukGgFNBhRIkvkjhvBHchQiF7lDgAFqrQwXZ0QPnmYlq80irPybvqFp x7YA9Wpn5j21rBWQ/P79c9/Ny9SscEoXacOndwN+e+l2nqB8eJX5DRxhhV1EKxZCi+KM scolMmc9rw7turGQ9CJmW0RXBYnPYI3YuqTVg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=7acCzk1+zYOdikz1rYM+I9HTPn/mSo41yDTPsye6fPA=; b=K5XVbs1GQnwhH4Q8I8BUPgSZffR4aD84RBb01L70aqNwlI5gAyRVNE3DFyP+w8mJ2e hlbHXNWxE9zqt4wKklUWg6gZ9lXZm8Ix3H13aEwz5o5jw8yCm9x1l/VbxZVG4V6WgCMt L/LfHYQQX03TYbd+fXJiUNa+9xsQHySPYxqWeFPJIQrkgKkzXJsfYocGEN1O5VbtiaRG Q54p0WVOhL8zTpQs941oNZxuEa8OstQaJF3dRAqx3+iM26aaYf4bIs0XiBek/pNjrcDV jwmpsr6e7zkt6zT/OVGJkXE2Wa97krd/C1amIZjWRHNYR7L4Qx9pJN3Aijevt5RFhvUl aQ1Q== X-Gm-Message-State: ANhLgQ01iYA/hgiGyjTTwX1WCZ27lohlmJp6puzthz+mjkuZvi1Tz66R ZBKtP5GyZDQdTWS9+ioyDgagGnqt1OY= X-Google-Smtp-Source: ADFU+vuEetSd4p2pJuwmKKo6ON0eLRsPK8oX3Ce30i6cwORDl+GZityfu7gSBRuwlalfNSdWI5tnZQ== X-Received: by 2002:a1c:2056:: with SMTP id g83mr242732wmg.179.1585337342288; Fri, 27 Mar 2020 12:29:02 -0700 (PDT) Received: from kpsingh-kernel.localdomain (77-56-209-237.dclient.hispeed.ch. [77.56.209.237]) by smtp.gmail.com with ESMTPSA id h132sm9828537wmf.18.2020.03.27.12.29.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Mar 2020 12:29:01 -0700 (PDT) From: KP Singh To: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-security-module@vger.kernel.org Cc: Andrii Nakryiko , Brendan Jackman , Florent Revest , Alexei Starovoitov , Daniel Borkmann , James Morris , Kees Cook , Paul Turner , Jann Horn , Florent Revest , Brendan Jackman , Greg Kroah-Hartman Subject: [PATCH bpf-next v8 4/8] bpf: lsm: Implement attach, detach and execution Date: Fri, 27 Mar 2020 20:28:50 +0100 Message-Id: <20200327192854.31150-5-kpsingh@chromium.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200327192854.31150-1-kpsingh@chromium.org> References: <20200327192854.31150-1-kpsingh@chromium.org> MIME-Version: 1.0 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: From: KP Singh JITed BPF programs are dynamically attached to the LSM hooks using BPF trampolines. The trampoline prologue generates code to handle conversion of the signature of the hook to the appropriate BPF context. The allocated trampoline programs are attached to the nop functions initialized as LSM hooks. BPF_PROG_TYPE_LSM programs must have a GPL compatible license and and need CAP_SYS_ADMIN (required for loading eBPF programs). Upon attachment: * A BPF fexit trampoline is used for LSM hooks with a void return type. * A BPF fmod_ret trampoline is used for LSM hooks which return an int. The attached programs can override the return value of the bpf LSM hook to indicate a MAC Policy decision. Signed-off-by: KP Singh Acked-by: Andrii Nakryiko Reviewed-by: Brendan Jackman Reviewed-by: Florent Revest Acked-by: James Morris --- include/linux/bpf_lsm.h | 11 ++++++++ kernel/bpf/bpf_lsm.c | 23 +++++++++++++++++ kernel/bpf/btf.c | 16 +++++++++++- kernel/bpf/syscall.c | 57 ++++++++++++++++++++++++++++------------- kernel/bpf/trampoline.c | 17 +++++++++--- kernel/bpf/verifier.c | 19 +++++++++++--- 6 files changed, 116 insertions(+), 27 deletions(-) diff --git a/include/linux/bpf_lsm.h b/include/linux/bpf_lsm.h index 83b96895829f..af74712af585 100644 --- a/include/linux/bpf_lsm.h +++ b/include/linux/bpf_lsm.h @@ -17,6 +17,17 @@ #include #undef LSM_HOOK +int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog, + const struct bpf_prog *prog); + +#else /* !CONFIG_BPF_LSM */ + +static inline int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog, + const struct bpf_prog *prog) +{ + return -EOPNOTSUPP; +} + #endif /* CONFIG_BPF_LSM */ #endif /* _LINUX_BPF_LSM_H */ diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index 3b3bbb28603e..19636703b24e 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -9,6 +9,8 @@ #include #include #include +#include +#include /* For every LSM hook that allows attachment of BPF programs, declare a nop * function where a BPF program can be attached. @@ -22,6 +24,27 @@ noinline RET bpf_lsm_##NAME(__VA_ARGS__) \ #include #undef LSM_HOOK +#define BPF_LSM_SYM_PREFX "bpf_lsm_" + +int bpf_lsm_verify_prog(struct bpf_verifier_log *vlog, + const struct bpf_prog *prog) +{ + if (!prog->gpl_compatible) { + bpf_log(vlog, + "LSM programs must have a GPL compatible license\n"); + return -EINVAL; + } + + if (strncmp(BPF_LSM_SYM_PREFX, prog->aux->attach_func_name, + sizeof(BPF_LSM_SYM_PREFX) - 1)) { + bpf_log(vlog, "attach_btf_id %u points to wrong type name %s\n", + prog->aux->attach_btf_id, prog->aux->attach_func_name); + return -EINVAL; + } + + return 0; +} + const struct bpf_prog_ops lsm_prog_ops = { }; diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 6f397c4da05e..de335cd386f0 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3710,7 +3710,21 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, } if (arg == nr_args) { - if (prog->expected_attach_type == BPF_TRACE_FEXIT) { + if (prog->expected_attach_type == BPF_TRACE_FEXIT || + prog->expected_attach_type == BPF_LSM_MAC) { + /* When LSM programs are attached to void LSM hooks + * they use FEXIT trampolines and when attached to + * int LSM hooks, they use MODIFY_RETURN trampolines. + * + * While the LSM programs are BPF_MODIFY_RETURN-like + * the check: + * + * if (ret_type != 'int') + * return -EINVAL; + * + * is _not_ done here. This is still safe as LSM hooks + * have only void and int return types. + */ if (!t) return true; t = btf_type_by_id(btf, t->type); diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index b2584b25748c..a616b63f23b4 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -25,6 +25,7 @@ #include #include #include +#include #define IS_FD_ARRAY(map) ((map)->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY || \ (map)->map_type == BPF_MAP_TYPE_CGROUP_ARRAY || \ @@ -1935,6 +1936,7 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type, switch (prog_type) { case BPF_PROG_TYPE_TRACING: + case BPF_PROG_TYPE_LSM: case BPF_PROG_TYPE_STRUCT_OPS: case BPF_PROG_TYPE_EXT: break; @@ -2366,10 +2368,28 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog) struct file *link_file; int link_fd, err; - if (prog->expected_attach_type != BPF_TRACE_FENTRY && - prog->expected_attach_type != BPF_TRACE_FEXIT && - prog->expected_attach_type != BPF_MODIFY_RETURN && - prog->type != BPF_PROG_TYPE_EXT) { + switch (prog->type) { + case BPF_PROG_TYPE_TRACING: + if (prog->expected_attach_type != BPF_TRACE_FENTRY && + prog->expected_attach_type != BPF_TRACE_FEXIT && + prog->expected_attach_type != BPF_MODIFY_RETURN) { + err = -EINVAL; + goto out_put_prog; + } + break; + case BPF_PROG_TYPE_EXT: + if (prog->expected_attach_type != 0) { + err = -EINVAL; + goto out_put_prog; + } + break; + case BPF_PROG_TYPE_LSM: + if (prog->expected_attach_type != BPF_LSM_MAC) { + err = -EINVAL; + goto out_put_prog; + } + break; + default: err = -EINVAL; goto out_put_prog; } @@ -2448,16 +2468,10 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr) if (IS_ERR(prog)) return PTR_ERR(prog); - if (prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT && - prog->type != BPF_PROG_TYPE_TRACING && - prog->type != BPF_PROG_TYPE_EXT && - prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) { - err = -EINVAL; - goto out_put_prog; - } - - if (prog->type == BPF_PROG_TYPE_TRACING || - prog->type == BPF_PROG_TYPE_EXT) { + switch (prog->type) { + case BPF_PROG_TYPE_TRACING: + case BPF_PROG_TYPE_EXT: + case BPF_PROG_TYPE_LSM: if (attr->raw_tracepoint.name) { /* The attach point for this category of programs * should be specified via btf_id during program load. @@ -2465,11 +2479,14 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr) err = -EINVAL; goto out_put_prog; } - if (prog->expected_attach_type == BPF_TRACE_RAW_TP) + if (prog->type == BPF_PROG_TYPE_TRACING && + prog->expected_attach_type == BPF_TRACE_RAW_TP) { tp_name = prog->aux->attach_func_name; - else - return bpf_tracing_prog_attach(prog); - } else { + break; + } + return bpf_tracing_prog_attach(prog); + case BPF_PROG_TYPE_RAW_TRACEPOINT: + case BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE: if (strncpy_from_user(buf, u64_to_user_ptr(attr->raw_tracepoint.name), sizeof(buf) - 1) < 0) { @@ -2478,6 +2495,10 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr) } buf[sizeof(buf) - 1] = 0; tp_name = buf; + break; + default: + err = -EINVAL; + goto out_put_prog; } btp = bpf_get_raw_tracepoint(tp_name); diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index f30bca2a4d01..9be85aa4ec5f 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -6,6 +6,7 @@ #include #include #include +#include /* dummy _ops. The verifier will operate on target program's ops. */ const struct bpf_verifier_ops bpf_extension_verifier_ops = { @@ -233,15 +234,23 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr) return err; } -static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(enum bpf_attach_type t) +static enum bpf_tramp_prog_type bpf_attach_type_to_tramp(struct bpf_prog *prog) { - switch (t) { + switch (prog->expected_attach_type) { case BPF_TRACE_FENTRY: return BPF_TRAMP_FENTRY; case BPF_MODIFY_RETURN: return BPF_TRAMP_MODIFY_RETURN; case BPF_TRACE_FEXIT: return BPF_TRAMP_FEXIT; + case BPF_LSM_MAC: + if (!prog->aux->attach_func_proto->type) + /* The function returns void, we cannot modify its + * return value. + */ + return BPF_TRAMP_FEXIT; + else + return BPF_TRAMP_MODIFY_RETURN; default: return BPF_TRAMP_REPLACE; } @@ -255,7 +264,7 @@ int bpf_trampoline_link_prog(struct bpf_prog *prog) int cnt; tr = prog->aux->trampoline; - kind = bpf_attach_type_to_tramp(prog->expected_attach_type); + kind = bpf_attach_type_to_tramp(prog); mutex_lock(&tr->mutex); if (tr->extension_prog) { /* cannot attach fentry/fexit if extension prog is attached. @@ -305,7 +314,7 @@ int bpf_trampoline_unlink_prog(struct bpf_prog *prog) int err; tr = prog->aux->trampoline; - kind = bpf_attach_type_to_tramp(prog->expected_attach_type); + kind = bpf_attach_type_to_tramp(prog); mutex_lock(&tr->mutex); if (kind == BPF_TRAMP_REPLACE) { WARN_ON_ONCE(!tr->extension_prog); diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2ea2a868324e..8808c06f2571 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -20,6 +20,7 @@ #include #include #include +#include #include "disasm.h" @@ -6488,8 +6489,9 @@ static int check_return_code(struct bpf_verifier_env *env) struct tnum range = tnum_range(0, 1); int err; - /* The struct_ops func-ptr's return type could be "void" */ - if (env->prog->type == BPF_PROG_TYPE_STRUCT_OPS && + /* LSM and struct_ops func-ptr's return type could be "void" */ + if ((env->prog->type == BPF_PROG_TYPE_STRUCT_OPS || + env->prog->type == BPF_PROG_TYPE_LSM) && !prog->aux->attach_func_proto->type) return 0; @@ -9919,7 +9921,9 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) if (prog->type == BPF_PROG_TYPE_STRUCT_OPS) return check_struct_ops_btf_id(env); - if (prog->type != BPF_PROG_TYPE_TRACING && !prog_extension) + if (prog->type != BPF_PROG_TYPE_TRACING && + prog->type != BPF_PROG_TYPE_LSM && + !prog_extension) return 0; if (!btf_id) { @@ -10050,8 +10054,16 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) return -EINVAL; /* fallthrough */ case BPF_MODIFY_RETURN: + case BPF_LSM_MAC: case BPF_TRACE_FENTRY: case BPF_TRACE_FEXIT: + prog->aux->attach_func_name = tname; + if (prog->type == BPF_PROG_TYPE_LSM) { + ret = bpf_lsm_verify_prog(&env->log, prog); + if (ret < 0) + return ret; + } + if (!btf_type_is_func(t)) { verbose(env, "attach_btf_id %u is not a function\n", btf_id); @@ -10066,7 +10078,6 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) tr = bpf_trampoline_lookup(key); if (!tr) return -ENOMEM; - prog->aux->attach_func_name = tname; /* t is either vmlinux type or another program's type */ prog->aux->attach_func_proto = t; mutex_lock(&tr->mutex);