netdev - [PATCH 08/11] bpf: Add BTF whitelist support

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Message-Id: <20200616100512.2168860-9-jolsa@kernel.org>
Date:   Tue, 16 Jun 2020 12:05:09 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Martin KaFai Lau <kafai@...com>,
        David Miller <davem@...hat.com>,
        John Fastabend <john.fastabend@...il.com>,
        Wenbo Zhang <ethercflow@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Andrii Nakryiko <andriin@...com>,
        Brendan Gregg <bgregg@...flix.com>,
        Florent Revest <revest@...omium.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 08/11] bpf: Add BTF whitelist support

Adding support to define 'whitelist' of BTF IDs, which is
also sorted.

Following defines sorted list of BTF IDs that is accessible
within kernel code as btf_whitelist_d_path and its count is
in btf_whitelist_d_path_cnt variable.

  extern int btf_whitelist_d_path[];
  extern int btf_whitelist_d_path_cnt;

  BTF_WHITELIST_ENTRY(btf_whitelist_d_path)
  BTF_ID(func, vfs_truncate)
  BTF_ID(func, vfs_fallocate)
  BTF_ID(func, dentry_open)
  BTF_ID(func, vfs_getattr)
  BTF_ID(func, filp_close)
  BTF_WHITELIST_END(btf_whitelist_d_path)

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 include/linux/bpf.h   |  3 +++
 kernel/bpf/btf.c      | 13 +++++++++++++
 kernel/bpf/btf_ids.h  | 38 ++++++++++++++++++++++++++++++++++++++
 kernel/bpf/verifier.c |  5 +++++
 4 files changed, 59 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e98c113a5d27..a94e85c2ec50 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -283,6 +283,7 @@ struct bpf_func_proto {
 		enum bpf_arg_type arg_type[5];
 	};
 	int *btf_id; /* BTF ids of arguments */
+	bool (*allowed)(const struct bpf_prog *prog);
 };
 
 /* bpf_context is intentionally undefined structure. Pointer to bpf_context is
@@ -1745,6 +1746,8 @@ enum bpf_text_poke_type {
 int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
 		       void *addr1, void *addr2);
 
+bool btf_whitelist_search(int id, int list[], int cnt);
+
 extern int bpf_skb_output_btf_ids[];
 extern int bpf_seq_printf_btf_ids[];
 extern int bpf_seq_write_btf_ids[];
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 6924180a19c4..feda74d232c5 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -20,6 +20,7 @@
 #include <linux/btf.h>
 #include <linux/skmsg.h>
 #include <linux/perf_event.h>
+#include <linux/bsearch.h>
 #include <net/sock.h>
 
 /* BTF (BPF Type Format) is the meta data format which describes
@@ -4669,3 +4670,15 @@ u32 btf_id(const struct btf *btf)
 {
 	return btf->id;
 }
+
+static int btf_id_cmp_func(const void *a, const void *b)
+{
+	const int *pa = a, *pb = b;
+
+	return *pa - *pb;
+}
+
+bool btf_whitelist_search(int id, int list[], int cnt)
+{
+	return bsearch(&id, list, cnt, sizeof(int), btf_id_cmp_func) != NULL;
+}
diff --git a/kernel/bpf/btf_ids.h b/kernel/bpf/btf_ids.h
index 68aa5c38a37f..a90c09faa515 100644
--- a/kernel/bpf/btf_ids.h
+++ b/kernel/bpf/btf_ids.h
@@ -67,4 +67,42 @@ asm(							\
 #name ":;                                      \n"	\
 ".popsection;                                  \n");
 
+
+/*
+ * The BTF_WHITELIST_ENTRY/END macros pair defines sorted
+ * list of BTF IDs plus its members count, with following
+ * layout:
+ *
+ * BTF_WHITELIST_ENTRY(list2)
+ * BTF_ID(type1, name1)
+ * BTF_ID(type2, name2)
+ * BTF_WHITELIST_END(list)
+ *
+ * __BTF_ID__sort__list:
+ * list2_cnt:
+ * .zero 4
+ * list2:
+ * __BTF_ID__type1__name1__3:
+ * .zero 4
+ * __BTF_ID__type2__name2__4:
+ * .zero 4
+ *
+ */
+#define BTF_WHITELIST_ENTRY(name)			\
+asm(							\
+".pushsection " SECTION ",\"a\";               \n"	\
+".global __BTF_ID__sort__" #name ";            \n"	\
+"__BTF_ID__sort__" #name ":;                   \n"	\
+".global " #name "_cnt;                        \n"	\
+#name "_cnt:;                                  \n"	\
+".zero 4                                       \n"	\
+".popsection;                                  \n");	\
+BTF_ID_LIST(name)
+
+#define BTF_WHITELIST_END(name)				\
+asm(							\
+".pushsection " SECTION ",\"a\";              \n"	\
+".size __BTF_ID__sort__" #name ", .-" #name " \n"	\
+".popsection;                                 \n");
+
 #endif
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index bee3da2cd945..5a9a6fd72907 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4633,6 +4633,11 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 		return -EINVAL;
 	}
 
+	if (fn->allowed && !fn->allowed(env->prog)) {
+		verbose(env, "helper call is not allowed in probe\n");
+		return -EINVAL;
+	}
+
 	/* With LD_ABS/IND some JITs save/restore skb from r1. */
 	changes_data = bpf_helper_changes_pkt_data(fn->func);
 	if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) {
-- 
2.25.4