selftests/bpf: Add return value checks for failed tests

The return ranges of some bpf lsm test progs can not be deduced by
the verifier accurately. To avoid erroneous rejections, add explicit
return value checks for these progs.

Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Link: https://lore.kernel.org/r/20240719110059.797546-8-xukuohai@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

4 files changed, 26 insertions, 3 deletions

diff --git a/tools/testing/selftests/bpf/progs/err.h b/tools/testing/selftests/bpf/progs/err.h
index d66d283d9e59..38529779a236 100644
--- a/tools/testing/selftests/bpf/progs/err.h
+++ b/tools/testing/selftests/bpf/progs/err.h
@@ -5,6 +5,16 @@
 #define MAX_ERRNO 4095
 #define IS_ERR_VALUE(x) (unsigned long)(void *)(x) >= (unsigned long)-MAX_ERRNO
 
+#define __STR(x) #x
+
+#define set_if_not_errno_or_zero(x, y)			\
+({							\
+	asm volatile ("if %0 s< -4095 goto +1\n"	\
+		      "if %0 s<= 0 goto +1\n"		\
+		      "%0 = " __STR(y) "\n"		\
+		      : "+r"(x));			\
+})
+
 static inline int IS_ERR_OR_NULL(const void *ptr)
 {
 	return !ptr || IS_ERR_VALUE((unsigned long)ptr);
diff --git a/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c b/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c
index 2f0eb1334d65..8ef6b39335b6 100644
--- a/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c
+++ b/tools/testing/selftests/bpf/progs/test_sig_in_xattr.c
@@ -6,6 +6,7 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 #include "bpf_kfuncs.h"
+#include "err.h"
 
 char _license[] SEC("license") = "GPL";
 
@@ -79,5 +80,8 @@ int BPF_PROG(test_file_open, struct file *f)
 	ret = bpf_verify_pkcs7_signature(&digest_ptr, &sig_ptr, trusted_keyring);
 
 	bpf_key_put(trusted_keyring);
+
+	set_if_not_errno_or_zero(ret, -EFAULT);
+
 	return ret;
 }
diff --git a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
index f42e9f3831a1..12034a73ee2d 100644
--- a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
+++ b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
@@ -11,6 +11,7 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 #include "bpf_kfuncs.h"
+#include "err.h"
 
 #define MAX_DATA_SIZE (1024 * 1024)
 #define MAX_SIG_SIZE 1024
@@ -55,12 +56,12 @@ int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
 
 	ret = bpf_probe_read_kernel(&value, sizeof(value), &attr->value);
 	if (ret)
-		return ret;
+		goto out;
 
 	ret = bpf_copy_from_user(data_val, sizeof(struct data),
 				 (void *)(unsigned long)value);
 	if (ret)
-		return ret;
+		goto out;
 
 	if (data_val->data_len > sizeof(data_val->data))
 		return -EINVAL;
@@ -84,5 +85,8 @@ int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
 
 	bpf_key_put(trusted_keyring);
 
+out:
+	set_if_not_errno_or_zero(ret, -EFAULT);
+
 	return ret;
 }
diff --git a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
index a9fc30ed4d73..20904cd2baa2 100644
--- a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
+++ b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c
@@ -7,6 +7,7 @@
 #include "bpf_misc.h"
 #include "xdp_metadata.h"
 #include "bpf_kfuncs.h"
+#include "err.h"
 
 /* The compiler may be able to detect the access to uninitialized
    memory in the routines performing out of bound memory accesses and
@@ -331,7 +332,11 @@ SEC("?lsm/bpf")
 __success __log_level(2)
 int BPF_PROG(arg_tag_ctx_lsm)
 {
-	return tracing_subprog_void(ctx) + tracing_subprog_u64(ctx);
+	int ret;
+
+	ret = tracing_subprog_void(ctx) + tracing_subprog_u64(ctx);
+	set_if_not_errno_or_zero(ret, -1);
+	return ret;
 }
 
 SEC("?struct_ops/test_1")