[RFC PATCH bpf-next v2 02/11] selftests/bpf: Test passing CONST_PTR_TO_DYNPTR to kfunc that may mutate dynptr

[Amery Hung <ameryhung@gmail.com>]

Make sure for kfunc that takes mutable dynptr argument, verifier rejects
passing CONST_PTR_TO_DYNPTR to it.

Rename struct sample to test_sample to avoid a conflict with the
definition in vmlinux.h

In test_kfunc_dynptr_param.c, initialize dynptr to 0 to avoid
-Wuninitialized-const-pointer warning.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
 .../testing/selftests/bpf/progs/dynptr_fail.c | 37 +++++++++++++++----
 .../bpf/progs/test_kfunc_dynptr_param.c       |  2 +-
 2 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index 8f2ae9640886..5e1b1cf4ea8e 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -1,15 +1,14 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2022 Facebook */
 
+#include <vmlinux.h>
 #include <errno.h>
 #include <string.h>
-#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"
+#include "../test_kmods/bpf_testmod_kfunc.h"
 
 char _license[] SEC("license") = "GPL";
 
@@ -46,7 +45,7 @@ struct {
 	__type(value, __u64);
 } array_map4 SEC(".maps");
 
-struct sample {
+struct test_sample {
 	int pid;
 	long value;
 	char comm[16];
@@ -95,7 +94,7 @@ __failure __msg("Unreleased reference id=4")
 int ringbuf_missing_release2(void *ctx)
 {
 	struct bpf_dynptr ptr1, ptr2;
-	struct sample *sample;
+	struct test_sample *sample;
 
 	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(*sample), 0, &ptr1);
 	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(*sample), 0, &ptr2);
@@ -173,7 +172,7 @@ __failure __msg("type=mem expected=ringbuf_mem")
 int ringbuf_invalid_api(void *ctx)
 {
 	struct bpf_dynptr ptr;
-	struct sample *sample;
+	struct test_sample *sample;
 
 	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(*sample), 0, &ptr);
 	sample = bpf_dynptr_data(&ptr, 0, sizeof(*sample));
@@ -315,7 +314,7 @@ __failure __msg("invalid mem access 'scalar'")
 int data_slice_use_after_release1(void *ctx)
 {
 	struct bpf_dynptr ptr;
-	struct sample *sample;
+	struct test_sample *sample;
 
 	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(*sample), 0, &ptr);
 	sample = bpf_dynptr_data(&ptr, 0, sizeof(*sample));
@@ -347,7 +346,7 @@ __failure __msg("invalid mem access 'scalar'")
 int data_slice_use_after_release2(void *ctx)
 {
 	struct bpf_dynptr ptr1, ptr2;
-	struct sample *sample;
+	struct test_sample *sample;
 
 	bpf_ringbuf_reserve_dynptr(&ringbuf, 64, 0, &ptr1);
 	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(*sample), 0, &ptr2);
@@ -1993,3 +1992,25 @@ int test_dynptr_reg_type(void *ctx)
 	global_call_bpf_dynptr((const struct bpf_dynptr *)current);
 	return 0;
 }
+
+/* Cannot pass CONST_PTR_TO_DYNPTR to bpf_kfunc_dynptr_test() that may mutate the dynptr */
+__noinline int global_subprog_dynptr_mutable(const struct bpf_dynptr *dynptr)
+{
+	long ret = 0;
+
+	/* this should fail */
+	bpf_kfunc_dynptr_test((struct bpf_dynptr *)dynptr, NULL);
+	__sink(ret);
+	return ret;
+}
+
+SEC("tc")
+__failure __msg("cannot pass pointer to const bpf_dynptr, the helper mutates it")
+int kfunc_dynptr_const_to_mutable(struct __sk_buff *skb)
+{
+	struct bpf_dynptr data;
+
+	bpf_dynptr_from_skb(skb, 0, &data);
+	global_subprog_dynptr_mutable(&data);
+	return 0;
+}
diff --git a/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
index c3631fd41977..1c6cfd0888ba 100644
--- a/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
+++ b/tools/testing/selftests/bpf/progs/test_kfunc_dynptr_param.c
@@ -33,7 +33,7 @@ SEC("?lsm.s/bpf")
 __failure __msg("cannot pass in dynptr at an offset=-8")
 int BPF_PROG(not_valid_dynptr, int cmd, union bpf_attr *attr, unsigned int size, bool kernel)
 {
-	unsigned long val;
+	unsigned long val = 0;
 
 	return bpf_verify_pkcs7_signature((struct bpf_dynptr *)&val,
 					  (struct bpf_dynptr *)&val, NULL);
-- 
2.47.3