Merge branch 'resolve_prog_type'

Udip Pant says:

====================
This patch series adds changes in verifier to make decisions such as granting
of read / write access or enforcement of return code status based on
the program type of the target program while using dynamic program
extension (of type BPF_PROG_TYPE_EXT).

The BPF_PROG_TYPE_EXT type can be used to extend types such as XDP, SKB
and others. Since the BPF_PROG_TYPE_EXT program type on itself is just a
placeholder for those, we need this extended check for those extended
programs to actually work with proper access, while using this option.

Patch #1 includes changes in the verifier.
Patch #2 adds selftests to verify write access on a packet for a valid
extension program type
Patch #3 adds selftests to verify proper check for the return code
Patch #4 adds selftests to ensure access permissions and restrictions
for some map types such sockmap.

Changelogs:
  v2 -> v3:
    * more comprehensive resolution of the program type in the verifier
      based on the target program (and not just for the packet access)
    * selftests for checking return code and map access
    * Also moved this patch to 'bpf-next' from 'bpf' tree
  v1 -> v2:
    * extraction of the logic to resolve prog type into a separate method
    * selftests to check for packet access for a valid freplace prog
====================

Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/verifier.c

@@ -2625,11 +2625,19 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
 
 #define MAX_PACKET_OFF 0xffff
 
+static enum bpf_prog_type resolve_prog_type(struct bpf_prog *prog)
+{
+	return prog->aux->linked_prog ? prog->aux->linked_prog->type
+				      : prog->type;
+}
+
 static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
 				       const struct bpf_call_arg_meta *meta,
 				       enum bpf_access_type t)
 {
-	switch (env->prog->type) {
+	enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
+
+	switch (prog_type) {
 	/* Program types only with direct read access go here! */
 	case BPF_PROG_TYPE_LWT_IN:
 	case BPF_PROG_TYPE_LWT_OUT:
@@ -4186,7 +4194,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id)
 {
 	enum bpf_attach_type eatype = env->prog->expected_attach_type;
-	enum bpf_prog_type type = env->prog->type;
+	enum bpf_prog_type type = resolve_prog_type(env->prog);
 
 	if (func_id != BPF_FUNC_map_update_elem)
 		return false;
@@ -7376,7 +7384,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	u8 mode = BPF_MODE(insn->code);
 	int i, err;
 
-	if (!may_access_skb(env->prog->type)) {
+	if (!may_access_skb(resolve_prog_type(env->prog))) {
 		verbose(env, "BPF_LD_[ABS|IND] instructions not allowed for this program type\n");
 		return -EINVAL;
 	}
@@ -7464,11 +7472,12 @@ static int check_return_code(struct bpf_verifier_env *env)
 	const struct bpf_prog *prog = env->prog;
 	struct bpf_reg_state *reg;
 	struct tnum range = tnum_range(0, 1);
+	enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
 	int err;
 
 	/* 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) &&
+	if ((prog_type == BPF_PROG_TYPE_STRUCT_OPS ||
+	     prog_type == BPF_PROG_TYPE_LSM) &&
 	    !prog->aux->attach_func_proto->type)
 		return 0;
 
@@ -7487,7 +7496,7 @@ static int check_return_code(struct bpf_verifier_env *env)
 		return -EACCES;
 	}
 
-	switch (env->prog->type) {
+	switch (prog_type) {
 	case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
 		if (env->prog->expected_attach_type == BPF_CGROUP_UDP4_RECVMSG ||
 		    env->prog->expected_attach_type == BPF_CGROUP_UDP6_RECVMSG ||
@@ -9243,6 +9252,7 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 					struct bpf_prog *prog)
 
 {
+	enum bpf_prog_type prog_type = resolve_prog_type(prog);
 	/*
 	 * Validate that trace type programs use preallocated hash maps.
 	 *
@@ -9260,8 +9270,8 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 	 * now, but warnings are emitted so developers are made aware of
 	 * the unsafety and can fix their programs before this is enforced.
 	 */
-	if (is_tracing_prog_type(prog->type) && !is_preallocated_map(map)) {
-		if (prog->type == BPF_PROG_TYPE_PERF_EVENT) {
+	if (is_tracing_prog_type(prog_type) && !is_preallocated_map(map)) {
+		if (prog_type == BPF_PROG_TYPE_PERF_EVENT) {
 			verbose(env, "perf_event programs can only use preallocated hash map\n");
 			return -EINVAL;
 		}
@@ -9273,8 +9283,8 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
 		verbose(env, "trace type programs with run-time allocated hash maps are unsafe. Switch to preallocated hash maps.\n");
 	}
 
-	if ((is_tracing_prog_type(prog->type) ||
-	     prog->type == BPF_PROG_TYPE_SOCKET_FILTER) &&
+	if ((is_tracing_prog_type(prog_type) ||
+	     prog_type == BPF_PROG_TYPE_SOCKET_FILTER) &&
 	    map_value_has_spin_lock(map)) {
 		verbose(env, "tracing progs cannot use bpf_spin_lock yet\n");
 		return -EINVAL;
@@ -9986,7 +9996,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 				insn->code = BPF_LDX | BPF_PROBE_MEM |
 					BPF_SIZE((insn)->code);
 				env->prog->aux->num_exentries++;
-			} else if (env->prog->type != BPF_PROG_TYPE_STRUCT_OPS) {
+			} else if (resolve_prog_type(env->prog) != BPF_PROG_TYPE_STRUCT_OPS) {
 				verbose(env, "Writes through BTF pointers are not allowed\n");
 				return -EINVAL;
 			}

tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c

@@ -123,6 +123,7 @@ static void test_func_replace(void)
 		"freplace/get_skb_len",
 		"freplace/get_skb_ifindex",
 		"freplace/get_constant",
+		"freplace/test_pkt_write_access_subprog",
 	};
 	test_fexit_bpf2bpf_common("./fexit_bpf2bpf.o",
 				  "./test_pkt_access.o",
@@ -141,10 +142,77 @@ static void test_func_replace_verify(void)
 				  prog_name, false);
 }
 
+static void test_func_sockmap_update(void)
+{
+	const char *prog_name[] = {
+		"freplace/cls_redirect",
+	};
+	test_fexit_bpf2bpf_common("./freplace_cls_redirect.o",
+				  "./test_cls_redirect.o",
+				  ARRAY_SIZE(prog_name),
+				  prog_name, false);
+}
+
+static void test_obj_load_failure_common(const char *obj_file,
+					  const char *target_obj_file)
+
+{
+	/*
+	 * standalone test that asserts failure to load freplace prog
+	 * because of invalid return code.
+	 */
+	struct bpf_object *obj = NULL, *pkt_obj;
+	int err, pkt_fd;
+	__u32 duration = 0;
+
+	err = bpf_prog_load(target_obj_file, BPF_PROG_TYPE_UNSPEC,
+			    &pkt_obj, &pkt_fd);
+	/* the target prog should load fine */
+	if (CHECK(err, "tgt_prog_load", "file %s err %d errno %d\n",
+		  target_obj_file, err, errno))
+		return;
+	DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts,
+			    .attach_prog_fd = pkt_fd,
+			   );
+
+	obj = bpf_object__open_file(obj_file, &opts);
+	if (CHECK(IS_ERR_OR_NULL(obj), "obj_open",
+		  "failed to open %s: %ld\n", obj_file,
+		  PTR_ERR(obj)))
+		goto close_prog;
+
+	/* It should fail to load the program */
+	err = bpf_object__load(obj);
+	if (CHECK(!err, "bpf_obj_load should fail", "err %d\n", err))
+		goto close_prog;
+
+close_prog:
+	if (!IS_ERR_OR_NULL(obj))
+		bpf_object__close(obj);
+	bpf_object__close(pkt_obj);
+}
+
+static void test_func_replace_return_code(void)
+{
+	/* test invalid return code in the replaced program */
+	test_obj_load_failure_common("./freplace_connect_v4_prog.o",
+				     "./connect4_prog.o");
+}
+
+static void test_func_map_prog_compatibility(void)
+{
+	/* test with spin lock map value in the replaced program */
+	test_obj_load_failure_common("./freplace_attach_probe.o",
+				     "./test_attach_probe.o");
+}
+
 void test_fexit_bpf2bpf(void)
 {
 	test_target_no_callees();
 	test_target_yes_callees();
 	test_func_replace();
 	test_func_replace_verify();
+	test_func_sockmap_update();
+	test_func_replace_return_code();
+	test_func_map_prog_compatibility();
 }

tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c

@@ -1,8 +1,10 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2019 Facebook */
 #include <linux/stddef.h>
+#include <linux/if_ether.h>
 #include <linux/ipv6.h>
 #include <linux/bpf.h>
+#include <linux/tcp.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_endian.h>
 #include <bpf/bpf_tracing.h>
@@ -151,4 +153,29 @@ int new_get_constant(long val)
 	test_get_constant = 1;
 	return test_get_constant; /* original get_constant() returns val - 122 */
 }
+
+__u64 test_pkt_write_access_subprog = 0;
+SEC("freplace/test_pkt_write_access_subprog")
+int new_test_pkt_write_access_subprog(struct __sk_buff *skb, __u32 off)
+{
+
+	void *data = (void *)(long)skb->data;
+	void *data_end = (void *)(long)skb->data_end;
+	struct tcphdr *tcp;
+
+	if (off > sizeof(struct ethhdr) + sizeof(struct ipv6hdr))
+		return -1;
+
+	tcp = data + off;
+	if (tcp + 1 > data_end)
+		return -1;
+
+	/* make modifications to the packet data */
+	tcp->check++;
+	tcp->syn = 0;
+
+	test_pkt_write_access_subprog = 1;
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/freplace_attach_probe.c

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+
+#include <linux/ptrace.h>
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#define VAR_NUM 2
+
+struct hmap_elem {
+	struct bpf_spin_lock lock;
+	int var[VAR_NUM];
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_HASH);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, struct hmap_elem);
+} hash_map SEC(".maps");
+
+SEC("freplace/handle_kprobe")
+int new_handle_kprobe(struct pt_regs *ctx)
+{
+	struct hmap_elem zero = {}, *val;
+	int key = 0;
+
+	val = bpf_map_lookup_elem(&hash_map, &key);
+	if (!val)
+		return 1;
+	/* spin_lock in hash map */
+	bpf_spin_lock(&val->lock);
+	val->var[0] = 99;
+	bpf_spin_unlock(&val->lock);
+
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/freplace_cls_redirect.c

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <linux/pkt_cls.h>
+#include <bpf/bpf_endian.h>
+#include <bpf/bpf_helpers.h>
+
+struct bpf_map_def SEC("maps") sock_map = {
+	.type = BPF_MAP_TYPE_SOCKMAP,
+	.key_size = sizeof(int),
+	.value_size = sizeof(int),
+	.max_entries = 2,
+};
+
+SEC("freplace/cls_redirect")
+int freplace_cls_redirect_test(struct __sk_buff *skb)
+{
+	int ret = 0;
+	const int zero = 0;
+	struct bpf_sock *sk;
+
+	sk = bpf_map_lookup_elem(&sock_map, &zero);
+	if (!sk)
+		return TC_ACT_SHOT;
+
+	ret = bpf_map_update_elem(&sock_map, &zero, sk, 0);
+	bpf_sk_release(sk);
+
+	return ret == 0 ? TC_ACT_OK : TC_ACT_SHOT;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/freplace_connect_v4_prog.c

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+
+#include <linux/stddef.h>
+#include <linux/ipv6.h>
+#include <linux/bpf.h>
+#include <linux/in.h>
+#include <sys/socket.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_endian.h>
+
+SEC("freplace/connect_v4_prog")
+int new_connect_v4_prog(struct bpf_sock_addr *ctx)
+{
+	// return value thats in invalid range
+	return 255;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/progs/test_pkt_access.c

@@ -79,6 +79,24 @@ int get_skb_ifindex(int val, struct __sk_buff *skb, int var)
 	return skb->ifindex * val * var;
 }
 
+__attribute__ ((noinline))
+int test_pkt_write_access_subprog(struct __sk_buff *skb, __u32 off)
+{
+	void *data = (void *)(long)skb->data;
+	void *data_end = (void *)(long)skb->data_end;
+	struct tcphdr *tcp = NULL;
+
+	if (off > sizeof(struct ethhdr) + sizeof(struct ipv6hdr))
+		return -1;
+
+	tcp = data + off;
+	if (tcp + 1 > data_end)
+		return -1;
+	/* make modification to the packet data */
+	tcp->check++;
+	return 0;
+}
+
 SEC("classifier/test_pkt_access")
 int test_pkt_access(struct __sk_buff *skb)
 {
@@ -117,6 +135,8 @@ int test_pkt_access(struct __sk_buff *skb)
 	if (test_pkt_access_subprog3(3, skb) != skb->len * 3 * skb->ifindex)
 		return TC_ACT_SHOT;
 	if (tcp) {
+		if (test_pkt_write_access_subprog(skb, (void *)tcp - data))
+			return TC_ACT_SHOT;
 		if (((void *)(tcp) + 20) > data_end || proto != 6)
 			return TC_ACT_SHOT;
 		barrier(); /* to force ordering of checks */