linux-kernel - [RFC][PATCH v2 6/7] selftests/bpf: Prevent positive ret values in test_lsm and verify_pkcs7

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Date:   Wed,  7 Dec 2022 18:24:33 +0100
From:   Roberto Sassu <roberto.sassu@...weicloud.com>
To:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...ux.dev, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, revest@...omium.org,
        jackmanb@...omium.org, mykolal@...com, paul@...l-moore.com,
        jmorris@...ei.org, serge@...lyn.com, shuah@...nel.org
Cc:     bpf@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [RFC][PATCH v2 6/7] selftests/bpf: Prevent positive ret values in test_lsm and verify_pkcs7_sig

From: Roberto Sassu <roberto.sassu@...wei.com>

Modify test_lsm and verify_pkcs7_sig to ensure that they don't return
positive values.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 tools/testing/selftests/bpf/progs/lsm.c               |  4 ++++
 .../selftests/bpf/progs/test_verify_pkcs7_sig.c       | 11 +++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/lsm.c b/tools/testing/selftests/bpf/progs/lsm.c
index d8d8af623bc2..42252750d866 100644
--- a/tools/testing/selftests/bpf/progs/lsm.c
+++ b/tools/testing/selftests/bpf/progs/lsm.c
@@ -88,6 +88,10 @@ SEC("lsm/file_mprotect")
 int BPF_PROG(test_int_hook, struct vm_area_struct *vma,
 	     unsigned long reqprot, unsigned long prot, int ret)
 {
+	/* file_mprotect hook must return zero or negative values. */
+	if (ret > 0)
+		ret = -EINVAL;
+
 	if (ret != 0)
 		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 ce419304ff1f..d3cab4370f29 100644
--- a/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
+++ b/tools/testing/selftests/bpf/progs/test_verify_pkcs7_sig.c
@@ -42,14 +42,14 @@ struct {
 char _license[] SEC("license") = "GPL";
 
 SEC("lsm.s/bpf")
-int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
+s64 BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
 {
 	struct bpf_dynptr data_ptr, sig_ptr;
 	struct data *data_val;
 	struct bpf_key *trusted_keyring;
 	__u32 pid;
 	__u64 value;
-	int ret, zero = 0;
+	s64 ret, zero = 0;
 
 	pid = bpf_get_current_pid_tgid() >> 32;
 	if (pid != monitored_pid)
@@ -86,5 +86,12 @@ int BPF_PROG(bpf, int cmd, union bpf_attr *attr, unsigned int size)
 
 	bpf_key_put(trusted_keyring);
 
+	/*
+	 * bpf hook must return zero or negative values, use s64 to propagate
+	 * the bounds to R0.
+	 */
+	if (ret > 0)
+		return -EINVAL;
+
 	return ret;
 }
-- 
2.25.1