From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexei Starovoitov Subject: [PATCH net-next 5/8] bpf: sanitize bpf tracepoint access Date: Mon, 4 Apr 2016 21:52:51 -0700 Message-ID: <1459831974-2891931-6-git-send-email-ast@fb.com> References: <1459831974-2891931-1-git-send-email-ast@fb.com> Mime-Version: 1.0 Content-Type: text/plain Cc: Peter Zijlstra , "David S . Miller" , Ingo Molnar , Daniel Borkmann , Arnaldo Carvalho de Melo , Wang Nan , Josef Bacik , Brendan Gregg , , , To: Steven Rostedt Return-path: Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:45933 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752996AbcDEEw5 (ORCPT ); Tue, 5 Apr 2016 00:52:57 -0400 Received: from pps.filterd (m0044008.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.11/8.16.0.11) with SMTP id u354pVVa008827 for ; Mon, 4 Apr 2016 21:52:56 -0700 Received: from mail.thefacebook.com ([199.201.64.23]) by mx0a-00082601.pphosted.com with ESMTP id 22468dr3wk-5 (version=TLSv1 cipher=AES128-SHA bits=128 verify=NOT) for ; Mon, 04 Apr 2016 21:52:56 -0700 Received: from facebook.com (2401:db00:11:d093:face:0:1b:0) by mx-out.facebook.com (10.102.107.99) with ESMTP id 42cd7f3afaea11e596ad0002c99293a0-6c5e23f0 for ; Mon, 04 Apr 2016 21:52:55 -0700 In-Reply-To: <1459831974-2891931-1-git-send-email-ast@fb.com> Sender: netdev-owner@vger.kernel.org List-ID: during bpf program loading remember the last byte of ctx access and at the time of attaching the program to tracepoint check that the program doesn't access bytes beyond defined in tracepoint fields This also disallows access to __dynamic_array fields, but can be relaxed in the future. Signed-off-by: Alexei Starovoitov --- include/linux/bpf.h | 1 + include/linux/trace_events.h | 1 + kernel/bpf/verifier.c | 6 +++++- kernel/events/core.c | 8 ++++++++ kernel/trace/trace_events.c | 18 ++++++++++++++++++ 5 files changed, 33 insertions(+), 1 deletion(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 198f6ace70ec..b2365a6eba3d 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -131,6 +131,7 @@ struct bpf_prog_type_list { struct bpf_prog_aux { atomic_t refcnt; u32 used_map_cnt; + u32 max_ctx_offset; const struct bpf_verifier_ops *ops; struct bpf_map **used_maps; struct bpf_prog *prog; diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 0810f81b6db2..97bd7da98567 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -569,6 +569,7 @@ extern int trace_define_field(struct trace_event_call *call, const char *type, int is_signed, int filter_type); extern int trace_add_event_call(struct trace_event_call *call); extern int trace_remove_event_call(struct trace_event_call *call); +extern int trace_event_get_offsets(struct trace_event_call *call); #define is_signed_type(type) (((type)(-1)) < (type)1) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 2e08f8e9b771..58792fed5678 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -652,8 +652,12 @@ static int check_ctx_access(struct verifier_env *env, int off, int size, enum bpf_access_type t) { if (env->prog->aux->ops->is_valid_access && - env->prog->aux->ops->is_valid_access(off, size, t)) + env->prog->aux->ops->is_valid_access(off, size, t)) { + /* remember the offset of last byte accessed in ctx */ + if (env->prog->aux->max_ctx_offset < off + size) + env->prog->aux->max_ctx_offset = off + size; return 0; + } verbose("invalid bpf_context access off=%d size=%d\n", off, size); return -EACCES; diff --git a/kernel/events/core.c b/kernel/events/core.c index 58fc9a7d1562..e7e3c2057582 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7131,6 +7131,14 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd) return -EINVAL; } + if (is_tracepoint) { + int off = trace_event_get_offsets(event->tp_event); + + if (prog->aux->max_ctx_offset > off) { + bpf_prog_put(prog); + return -EACCES; + } + } event->tp_event->prog = prog; return 0; diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 05ddc0820771..ced963049e0a 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -204,6 +204,24 @@ static void trace_destroy_fields(struct trace_event_call *call) } } +/* + * run-time version of trace_event_get_offsets_() that returns the last + * accessible offset of trace fields excluding __dynamic_array bytes + */ +int trace_event_get_offsets(struct trace_event_call *call) +{ + struct ftrace_event_field *tail; + struct list_head *head; + + head = trace_get_fields(call); + /* + * head->next points to the last field with the largest offset, + * since it was added last by trace_define_field() + */ + tail = list_first_entry(head, struct ftrace_event_field, link); + return tail->offset + tail->size; +} + int trace_event_raw_init(struct trace_event_call *call) { int id; -- 2.8.0