Re: [PATCH bpf-next 2/2] selftests/bpf: Expand skb dynptr selftests for tp_btf

Martin KaFai Lau <martin.lau@xxxxxxxxx> · Mon, 6 May 2024 14:43:50 -0700

On 4/30/24 5:18 AM, Philo Lu wrote:
Add 3 test cases for skb dynptr used in tp_btf:
- test_dynptr_skb_tp_btf: use skb dynptr in tp_btf and make sure it is
   read-only.
- skb_invalid_ctx_fentry/skb_invalid_ctx_fexit: bpf_dynptr_from_skb
   should fail in fentry/fexit.

In test_dynptr_skb_tp_btf, to trigger the tracepoint in kfree_skb,
test_pkt_access is used for its test_run, as in kfree_skb.c. Because the
test process is different from others, a new setup type is defined,
i.e., SETUP_SKB_PROG_TP.

The result is like:
$ ./test_progs -t 'dynptr/test_dynptr_skb_tp_btf'
   #77/14   dynptr/test_dynptr_skb_tp_btf:OK
   #77      dynptr:OK
   #120     kfunc_dynptr_param:OK
   Summary: 2/1 PASSED, 0 SKIPPED, 0 FAILED

$ ./test_progs -t 'dynptr/skb_invalid_ctx_f'
   #77/83   dynptr/skb_invalid_ctx_fentry:OK
   #77/84   dynptr/skb_invalid_ctx_fexit:OK
   #77      dynptr:OK
   #120     kfunc_dynptr_param:OK
   Summary: 2/2 PASSED, 0 SKIPPED, 0 FAILED

Also fix two coding style nits (change spaces to tabs).

Signed-off-by: Philo Lu <lulie@xxxxxxxxxxxxxxxxx>
---
  .../testing/selftests/bpf/prog_tests/dynptr.c | 36 +++++++++++++++++--
  .../testing/selftests/bpf/progs/dynptr_fail.c | 25 +++++++++++++
  .../selftests/bpf/progs/dynptr_success.c      | 23 ++++++++++++
  3 files changed, 82 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/dynptr.c b/tools/testing/selftests/bpf/prog_tests/dynptr.c
index 7cfac53c0d58..ba40be8b1c4e 100644
--- a/tools/testing/selftests/bpf/prog_tests/dynptr.c
+++ b/tools/testing/selftests/bpf/prog_tests/dynptr.c
@@ -9,6 +9,7 @@
  enum test_setup_type {
  	SETUP_SYSCALL_SLEEP,
  	SETUP_SKB_PROG,
+	SETUP_SKB_PROG_TP,
  };
  
  static struct {
@@ -28,6 +29,7 @@ static struct {
  	{"test_dynptr_clone", SETUP_SKB_PROG},
  	{"test_dynptr_skb_no_buff", SETUP_SKB_PROG},
  	{"test_dynptr_skb_strcmp", SETUP_SKB_PROG},
+	{"test_dynptr_skb_tp_btf", SETUP_SKB_PROG_TP},
  };
  
  static void verify_success(const char *prog_name, enum test_setup_type setup_type)
@@ -35,7 +37,7 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
  	struct dynptr_success *skel;
  	struct bpf_program *prog;
  	struct bpf_link *link;
-       int err;
+	int err;
  
  	skel = dynptr_success__open();
  	if (!ASSERT_OK_PTR(skel, "dynptr_success__open"))
@@ -47,7 +49,7 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
  	if (!ASSERT_OK_PTR(prog, "bpf_object__find_program_by_name"))
  		goto cleanup;
  
-       bpf_program__set_autoload(prog, true);
+	bpf_program__set_autoload(prog, true);
  
  	err = dynptr_success__load(skel);
  	if (!ASSERT_OK(err, "dynptr_success__load"))
@@ -87,6 +89,36 @@ static void verify_success(const char *prog_name, enum test_setup_type setup_typ
  
  		break;
  	}
+	case SETUP_SKB_PROG_TP:
+	{
+		struct __sk_buff skb = {};
+		struct bpf_object *obj;
+		int aux_prog_fd;
+
+		/* Just use its test_run to trigger kfree_skb tracepoint */
+		err = bpf_prog_test_load("./test_pkt_access.bpf.o", BPF_PROG_TYPE_SCHED_CLS,
+					 &obj, &aux_prog_fd);
+		if (!ASSERT_OK(err, "prog_load sched cls"))
+			goto cleanup;
+
+		LIBBPF_OPTS(bpf_test_run_opts, topts,
+			    .data_in = &pkt_v4,
+			    .data_size_in = sizeof(pkt_v4),
+			    .ctx_in = &skb,
+			    .ctx_size_in = sizeof(skb),
+		);
+
+		link = bpf_program__attach(prog);
+		if (!ASSERT_OK_PTR(link, "bpf_program__attach"))
+			goto cleanup;
+
+		err = bpf_prog_test_run_opts(aux_prog_fd, &topts);
+
+		if (!ASSERT_OK(err, "test_run"))
+			goto cleanup;
+
+		break;
+	}
  	}
  
  	ASSERT_EQ(skel->bss->err, 0, "err");
diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index 7ce7e827d5f0..c438d1c3cac5 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -6,6 +6,7 @@
  #include <stdbool.h>
  #include <linux/bpf.h>
  #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
  #include <linux/if_ether.h>
  #include "bpf_misc.h"
  #include "bpf_kfuncs.h"
@@ -1254,6 +1255,30 @@ int skb_invalid_ctx(void *ctx)
  	return 0;
  }
  
+SEC("fentry/skb_tx_error")
+__failure __msg("must be referenced or trusted")
+int BPF_PROG(skb_invalid_ctx_fentry, struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	return 0;
+}
+
+SEC("fexit/skb_tx_error")
+__failure __msg("must be referenced or trusted")
+int BPF_PROG(skb_invalid_ctx_fexit, struct __sk_buff *skb)
+{
+	struct bpf_dynptr ptr;
+
+	/* this should fail */
+	bpf_dynptr_from_skb(skb, 0, &ptr);
+
+	return 0;
+}
+
  /* Reject writes to dynptr slot for uninit arg */
  SEC("?raw_tp")
  __failure __msg("potential write to dynptr at off=-16")
diff --git a/tools/testing/selftests/bpf/progs/dynptr_success.c b/tools/testing/selftests/bpf/progs/dynptr_success.c
index 5985920d162e..8faafab97c0e 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_success.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_success.c
@@ -5,6 +5,7 @@
  #include <stdbool.h>
  #include <linux/bpf.h>
  #include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
  #include "bpf_misc.h"
  #include "bpf_kfuncs.h"
  #include "errno.h"
@@ -544,3 +545,25 @@ int test_dynptr_skb_strcmp(struct __sk_buff *skb)
  
  	return 1;
  }
+
+SEC("tp_btf/kfree_skb")
+int BPF_PROG(test_dynptr_skb_tp_btf, struct __sk_buff *skb, void *location)

struct __sk_buff is the incorrect type. This happens to work but will be a 
surprise for people trying to read something (e.g. skb->len). The same goes for 
the ones in dynptr_fail.c.

+{
+	__u8 write_data[2] = {1, 2};
+	struct bpf_dynptr ptr;
+	int ret;
+
+	if (bpf_dynptr_from_skb(skb, 0, &ptr)) {
+		err = 1;
+		return 1;
+	}
+
+	/* since tp_btf skbs are read only, writes should fail */
+	ret = bpf_dynptr_write(&ptr, 0, write_data, sizeof(write_data), 0);
+	if (ret != -EINVAL) {
+		err = 2;
+		return 1;
+	}
+
+	return 1;
+}








